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Content uploaded by Kenneth Alper
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All content in this area was uploaded by Kenneth Alper on Oct 24, 2018
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——Chapter 1——
IBOGAINE: A REVIEW
Kenneth R. Alper
Departments of Psychiatry and Neurology
New York University School of Medicine
New York, NY 10016
I. Introduction, Chemical Properties, and Historical Time Line ....................................
A. Introduction............................................................................................................
B. Chemical Structure and Properties ........................................................................
C. Historical Time Line ..............................................................................................
II. Mechanisms of Action.................................................................................................
A. Neurotransmitter Activities....................................................................................
B. Discrimination Studies...........................................................................................
C. Effects on Neuropeptides.......................................................................................
D. Possible Effects on Neuroadaptations Related to Drug Sensitization
or Tolerance ...........................................................................................................
III. Evidence of Efficacy in Animal Models.......................................................................
A. Drug Self-Administration ......................................................................................
B. Acute Opioid Withdrawal......................................................................................
C. Conditioned Place Preference................................................................................
D. Locomotor Activity................................................................................................
E. Dopamine Efflux....................................................................................................
IV Evidence of Efficacy and Subjective Effects in Humans............................................
A. Evidence of Efficacy..............................................................................................
B. Subjective Effects ..................................................................................................
V. Pharmacokinetics .........................................................................................................
A. Absorption..............................................................................................................
B. Distribution ............................................................................................................
C. Metabolism ............................................................................................................
D. Excretion................................................................................................................
VI. Safety ...........................................................................................................................
A. Neurotoxicity .........................................................................................................
B. Cardiovascular Effects ...........................................................................................
C. Fatalities.................................................................................................................
D. Abuse Liability ......................................................................................................
VII. Learning, Memory, and Neurophysiology...................................................................
A. Learning, Memory, and Addiction.........................................................................
B. Effects of Ibogaine on Learning and Memory ......................................................
C. Ibogaine and the EEG ............................................................................................
D. Goutarel’s Hypothesis............................................................................................
VIII. Anthropological and Sociological Perspectives ..........................................................
THE ALKALOIDS, Vol.56 Copyright © 2001 by Academic Press
0099-9598/01 $35.00 All rights of reproduction in any form reserved
1
IX. Economic and Political Perspectives...........................................................................
A. Economic Incentives and the Development of Ibogaine.......................................
B. Political Issues .......................................................................................................
X. Conclusions..................................................................................................................
References....................................................................................................................
I. Introduction and Historical Time Line
A. Introduction
Ibogaine, a naturally occurring plant alkaloid with a history of use as a
medicinal and ceremonial agent in West Central Africa, has been alleged to be
effective in the treatment of drug abuse. The National Institute on Drug Abuse
(NIDA) has given significant support to animal research, and the U.S. Food and
Drug Administration (FDA) has approved Phase I studies in humans. Evidence
for ibogaine’s effectiveness includes a substantial preclinical literature on
reduced drug self-administration and withdrawal in animals, and case reports in
humans. There is relatively little financial incentive for its development by the
pharmaceutical industry because ibogaine is isolated from a botanical source in
which it naturally occurs, and its chemical structure cannot be patented. This has
left the academic community and the public sector with a crucial role in research
on ibogaine, which was a major reason for organizing the First International
Conference on Ibogaine.
A major focus of the Conference was the possible mechanism(s) of action of
ibogaine. Ibogaine is of interest because it appears to have a novel mechanism of
action distinct from other existing pharmacotherapeutic approaches to addiction,
and it potentially could provide a paradigm for understanding the neurobiology
of addiction and the development of new treatments. Another important focus of
the Conference was to review human experience with ibogaine and preclinical
and clinical evidence of efficacy and safety. The Conference also featured presen-
tations related to the sociological and anthropological aspects of the sacramental
context of the use of iboga in Africa and the distinctive ibogaine subculture of the
United States and Europe.
B. Chemical Structure and Properties
Ibogaine (10-methoxyibogamine) (Figure 1) is an indole alkaloid with
molecular formula C20H26N20 and molecular weight 310.44. Ibogaine is the most
abundant alkaloid in the root bark of the Apocynaceous shrub Tabernanthe iboga,
which grows in West Central Africa. In the dried root bark, the part of the plant
2kenneth r. alper
in which alkaloid content is highest, total alkaloid content is reportedly 5 to 6%
(1).
Ibogaine has a melting point of 153°, a pKaof 8.1 in 80% methylcellosolve,
and it crystallizes as prismatic needles from ethanol. Ibogaine is levorotatory [α]D
–53°(in 95% ethanol), soluble in ethanol, ether, chloroform, acetone and
benzene, but it is practically insoluble in water. Ibogaine is decomposed by the
action of heat and light. Ibogaine hydrochloride decomposes at 299°, is also
levorotatory [α]D–63°(ethanol), [α]D–49°(H2O), and is soluble in water,
methanol, and ethanol, slightly soluble in acetone and chloroform, and practically
insoluble in ether (2). The X-ray crystal analysis that confirmed the structure of
ibogaine has been described (3). The literature provides references to the mass
spectrum of ibogaine (4), and the proton (5,6) and the 13C (7-9) NMR spectra of
ibogaine and other iboga alkaloids. Analytic chemical methods for extraction,
derivatization, and detection of ibogaine utilizing combined gas chromatography-
mass spectometry have been described (10-13).
Ibogaine undergoes demethylation to form its principal metabolite,
noribogaine, also known as O-desmethylibogaine or 10-hydroxyibogamine. 18-
methoxycoronaridine (18-MC, see Glick et al. in this volume) is an ibogaine
congener that appears to have efficacy similar to ibogaine in animal models of
drug dependence with evidence of less potential toxicity.
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1. ibogaine: a review
Alkaloid R1R2R3
Ibogaine OCH3HH
Noribogaine OH H H
(+)-18-Methoxycoronaridine H CO2CH3OCH3
Figure 1. Chemical Structures of Ibogaine, Noribogaine, and 18-Methoxycoronaridine.
The ibogamine skeleton above is numbered using the LeMen and Taylor system in which ibogaine is
designated as 10-methoxyibogamine and noribogaine as 10-hydroxyibogamine. Alternatively,
according to the Chemical Abstracts numbering system for the ibogamine skeleton which is
frequently encountered in the biological and medical literature, ibogaine and noribogaine have respec-
tively been referred to as 12-methoxyibogamine and 12-hydroxyibogamine.
C. Historical Time Line
The following timeline outlines the historical events relating to the
development of ibogaine as a treatment for drug dependence. Elsewhere in this
volume, Alper et al. provide a more detailed contemporary history of ibogaine in
the United States and Europe.
1864: The first description of T. iboga is published. A specimen is brought to
France from Gabon. A published description of the ceremonial use of T. iboga in
Gabon appears in 1885 (14).
1901: Ibogaine is isolated and crystallized from T. iboga root bark (15-17).
1901-1905: The first pharmacodynamic studies of ibogaine are performed.
During this period ibogaine is recommended as a treatment for “asthenia” at a
dosage range of 10 to 30 mg per day (14).
1939-1970: Ibogaine is sold in France as Lambarène, a “neuromuscular
stimulant,” in 8 mg tablets, recommended for indications that include fatigue,
depression, and recovery from infectious disease (14).
1955: Harris Isbell administers doses of ibogaine of up to 300 mg to eight
already detoxified morphine addicts at the U.S. Addiction Research Center in
Lexington, Kentucky (18).
1957: The description of the definitive chemical structure of ibogaine is
published. The total synthesis of ibogaine is reported in 1965 (19-21).
1962-1963: In the United States, Howard Lotsof administers ibogaine to 19
individuals at dosages of 6 to 19 mg/kg, including 7 with opioid dependence who
note an apparent effect on acute withdrawal symptomatology (22,23).
1967-1970: The World Health Assembly classifies ibogaine with hallucinogens
and stimulants as a “substance likely to cause dependency or endanger human
health.” The U.S. Food and Drug Administration (FDA) assigns ibogaine
Schedule I classification. The International Olympic Committee bans ibogaine as
a potential doping agent. Sales of Lambarène cease in France (14).
1969: Dr. Claudio Naranjo, a psychiatrist, receives a French patent for the
psychotherapeutic use of ibogaine at a dosage of 4 to 5 mg/kg (24).
1985: Howard Lotsof receives a U.S. patent for the use of ibogaine in opioid
4kenneth r. alper
withdrawal (22). Additional patents follow for indications of dependence on
cocaine and other stimulants (23), alcohol (25), nicotine (26), and polysubstance
abuse (27).
1988-1994: U.S. and Dutch researchers publish initial findings suggestive of
the efficacy of ibogaine in animal models of addiction, including diminished
opioid self-administration and withdrawal (28-30), as well as diminished cocaine
self-administration (31).
1989-1993: Treatments are conducted outside of conventional medical settings
in the Netherlands involving the International Coalition of Addict Self-Help
(ICASH), Dutch Addict Self Help (DASH), and NDA International (22,32-35).
1991: Based on case reports and preclinical evidence suggesting possible
efficacy, NIDA Medication Development Division (MDD) begins its ibogaine
project. The major objectives of the ibogaine project are preclinical toxicological
evaluation and development of a human protocol.
August 1993: FDA Advisory Panel meeting, chaired by Medical Review
Officer Curtis Wright, is held to formally consider Investigational New Drug
Application filed by Dr. Deborah Mash, Professor of Neurology at the University
of Miami School of Medicine. Approval is given for human trials. The approved
ibogaine dosage levels are 1, 2, and 5 mg/kg. The Phase I dose escalation study
begins December 1993, but activity is eventually suspended (36).
October 1993-December 1994: The National Institute on Drug Abuse (NIDA)
holds a total of four Phase I/II protocol development meetings, which include
outside consultants. The resulting draft protocol calls for the single adminis-
tration of fixed dosages of ibogaine of 150 and 300 mg versus placebo for the
indication of cocaine dependence (37).
March 1995: The NIDA Ibogaine Review Meeting is held in Rockville,
Maryland, chaired by the MDD Deputy Director, Dr. Frank Vocci. The possibility
of NIDA funding a human trial of the efficacy of ibogaine is considered. Opinions
of representatives of the pharmaceutical industry are mostly critical, and are a
significant influence in the decision not to fund the trial. NIDA ends its ibogaine
project, but it does continue to support some preclinical research on iboga
alkaloids.
Mid 1990s-2001: Ibogaine becomes increasingly available in alternative
settings, in view of the lack of approval in the Europe and the United States.
Treatments in settings based on a conventional medical model are conducted in
5
1. ibogaine: a review
Panama in 1994 and 1995 and in St. Kitts from 1996 to the present. Informal
scenes begin in the United States, Slovenia, Britain, the Netherlands, and the
Czech Republic. The Ibogaine Mailing List (38) begins in 1997 and heralds an
increasing utilization of the Internet within the ibogaine medical subculture.
II. Mechanisms of Action
A. Neurotransmitter Activities
1. General Comments
Elsewhere in this volume, Glick et al., Sershen et al., and Skolnick review the
mechanism of action of ibogaine. Popik and Skolnick (39) provide a recent,
detailed review of ibogaine’s receptor activities. Ibogaine appears to have a novel
mechanism of action that differs from other existing pharmacotherapies of
addiction, and its mechanism of action does not appear to be readily explained on
the basis of existing pharmacologic approaches to addiction. Ibogaine’s effects
may result from complex interactions between multiple neurotransmitter systems
rather than predominant activity within a single neurotransmitter system (39-42).
Several laboratories have reported on the results of pharmacological screens of
the receptor binding profile of ibogaine (40,43-45). Ibogaine has low micromolar
affinities for multiple binding sites within the central nervous system, including
N-methyl-D-aspartate (NMDA), kappa- and mu-opioid and sigma2receptors,
sodium channels, and the serotonin transporter. Although not apparent in binding
studies, functional studies indicate significant activity of ibogaine as a noncom-
petitive antagonist at the nicotinic acetylcholine receptor (46-50).
Although in vitro activities in the micromolar range are often described as
ancillary in attempting to characterize a drug’s in vivo mechanism of action,
micromolar activity may be pharmacologically important with regard to ibogaine
or noribogaine due to the relatively high concentrations reached in the brain
(40,44,51). Hough et al. (51) noted a brain level of ibogaine of 10 µM in female
rats at 1 hour after the administration of 40 mg/kg ibogaine i.p., which is the usual
dosage, animal, gender and route of administration used in that laboratory to
investigate ibogaine’s effects on drug self-administration and withdrawal. Brain
levels of ibogaine, and its major metabolite noribogaine, ranged from 1 to 17 µM
between 15 minutes and 2 hours in male rats following the oral administration
ibogaine at a dose of 50 mg/kg (44).
2. Glutamate
Elsewhere in this volume, Skolnick reviews the possible relevance of
6kenneth r. alper
ibogaine’s activity as a glutamate antagonist to its putative effects in drug
dependence. There is evidence that suggests that antagonists of the N-methyl-D-
aspartate (NMDA) subtype of glutamate receptor are a potentially promising
class of agents for the development of medications for addiction (52-54).
Ibogaine’s apparent activity as a noncompetitive NMDA antagonist has been
suggested to be a possible mechanism mediating its putative effects on drug
dependence (39,41,55-58).
Ibogaine competitively inhibits the binding of the NMDA antagonist MK801
to the NMDA receptor complex, with reported affinities in the range of 0.02 to
9.8 µM (40,45,55-57,59,60). Functional evidence supporting an antagonist action
of ibogaine at the NMDA receptor includes observations of reduced glutamate-
induced cell death in neuronal cultures, reduction of NMDA-activated currents in
hippocampal cultures (55,58), prevention of NMDA-mediated depolarization in
frog motoneurons (59), and protection against NMDA-induced convulsions (61).
Glycine, which acts as an NMDA co-agonist by binding at the NMDA receptor,
attenuates ibogaine’s effect of blocking naloxone-precipitated jumping (58).
MK801 and ibogaine do not produce identical effects, as evidenced by the
observation that in the rat brain ibogaine lowered the concentration of dopamine
while increasing the level of its metabolites, whereas MK801 did not have these
effects (62,63).
3. Opioids
It has been suggested that ibogaine’s or noribogaine’s activity as a putative
agonist at mu-opioid receptors might explain ibogaine’s apparent efficacy in
opioid withdrawal (36,64,65). Ibogaine binds to mu-opioid receptors with
reported binding affinities in the range of 0.13 to 26 µM (40,45,64,66), with one
study reporting a result in excess of 100 µM (43). Ibogaine behaves as an agonist
in a functional assay for mu-opioid receptors, the binding of [35S]-GTPγS (65).
However, some observations are difficult to reconcile with a mu-agonist action of
ibogaine. Ibogaine did not behave as a mu-opioid agonist in assays with isolated
smooth muscle preparations (67). Unlike mu-opioid agonists, ibogaine (68-70)
and noribogaine (71) do not appear by themselves to have antinociceptive effects.
Some findings suggest the intriguing possibility that ibogaine may act at the
level of second messenger signal transduction to enhance the functional activity
of mu-opioid receptors independently of any direct agonist interaction at opioid
receptors. Both ibogaine and noribogaine reportedly potentiated morphine-
induced inhibition of adenylate cyclase in vitro with opioid receptors already
occupied by the maximally effective concentration of morphine, but did not affect
adenylate cyclase in the absence of morphine (72). A similar interpretation might
also explain the finding that ibogaine inhibited the development of tolerance to
the antinociceptive effect of morphine in mice, without by itself affecting
nociception (73).
7
1. ibogaine: a review
Ibogaine binds to kappa-opioid receptors with reported binding affinities in the
range of 2.2 to 30 µM (43,45,56,66). Evidence consistent with a kappa-opioid
action of ibogaine includes the observation that the kappa-opioid antagonist,
norbinaltorphimine antagonized some of the effects of ibogaine in morphine-
treated rats (74,75). Kappa-opioid agonists reportedly can imitate certain effects
of ibogaine, such as reduced cocaine and morphine self-administration (76), and
reduction in locomotor activation to morphine accentuated by prior morphine
exposure (77). Sershen, on the other hand, attributes a kappa-opioid antagonist
action to ibogaine, based on the observation that stimulated dopamine efflux from
mouse brain slices was decreased by a kappa opioid agonist, and the decrease was
offset by the addition of ibogaine (78). However, ibogaine’s interactions with
multiple neurotransmitter systems raises the possibility that the finding could be
accounted for by mechanisms that do not involve the kappa-opioid receptor, as
dopamine efflux is modulated by multiple neurotransmitters.
4. Serotonin
Ibogaine and serotonin both contain an indole ring in their structure, and
ibogaine has been shown to bind to the serotonin transporter and to increase
serotonin levels in the nucleus accumbens (NAc) (41,79,80). The demonstration
that ibogaine blocks serotonin uptake (81) suggests that the effect of ibogaine on
extracellular serotonin levels may be mediated by uptake inhibition, in addition
to release (80). The reported affinity of ibogaine for the serotonin transporter
ranges from 0.55 to 10 µM (39,44,45,79,81), and the affinity of noribogaine for
the serotonin transporter is approximately 10-fold stronger (45,79). The
magnitude of the effect of ibogaine on serotonin release is reportedly large and is
comparable to that of the serotonin releasing agent fenfluramine, with
noribogaine having a lesser effect, and 18-MC no effect (80). Some authors
suggest a role for modulatory influence of serotonin in ibogaine’s effects on
dampening dopamine efflux in the NAc (41,80).
Ibogaine’s hallucinogenic effect has been suggested to involve altered
serotonergic neurotransmission (42,80). Ibogaine is reported in some studies to
bind the 5-HT2A receptor, which is thought to mediate the effects of “classical”
indolealkylamine and phenethylamine hallucinogens (82), with three studies
reporting affinities in the range of 4.1 to 12 µM (40,45,83), one reporting a value
of 92.5 µM (84), and with two other studies reporting no significant affinity
(43,44). Drug discrimination studies provide some functional evidence for the
action of ibogaine as an agonist at the 5-HT2A receptor, which is apparently a
significant, although nonessential, determinant of the ibogaine stimulus (84) (see
Section II.B, “Discrimination Studies”). Ibogaine binds to the 5-HT3receptor
with reported affinities of 2.6 and 3.9 µM (40,45), and it was without significant
affinity in two other studies (43,83). The 5-HT3receptor is apparently not
involved in the ibogaine discriminative stimulus (85).
8kenneth r. alper
5. Dopamine
Ibogaine does not appear to significantly affect radioligand binding to D1, D2,
D3, or D4receptors (40,43,44) and is a competitive blocker of dopamine uptake
at the dopamine transporter with affinities in the range of 1.5 to 20 µM (81).
Where affinities for the serotonin and dopamine transporter have been estimated
within the same study, the reported affinity of ibogaine for the serotonin
transporter has generally been 10 to 50 times stronger than its affinity for the
dopamine transporter (44,79,81). Ibogaine does not apparently affect norepi-
nephrine reuptake (44,45).
French et al. (86) studied the electrophysiological activity of dopamine
neurons in the ventral tegmental area (VTA) of rats given up to 7.5 mg/kg
ibogaine intravenously and found a significant increase in firing rate. Ibogaine
given intraperitoneally (i.p.) at a dose of 40 mg/kg did not affect the spontaneous
firing of VTA dopamine neurons or the response of VTA dopamine neurons to
cocaine or morphine. Ibogaine reportedly lowers the concentration of dopamine,
while increasing the level of its metabolites, indicating diminished release of
dopamine in the brain of the rat (62,63) and the mouse (87). Decreased release of
dopamine could possibly explain the observation of increased prolactin release
following ibogaine administration (62,63,88). Staley et al. (44) have suggested
that ibogaine might act at the dopamine transporter to inhibit the translocation of
dopamine into synaptic vesicles, thereby redistributing dopamine from vesicular
to cytoplasmic pools. As a result, the metabolism of dopamine by monoamine
oxidase could explain the observation of decreased tissue dopamine content with
increased levels of its metabolites.
The effects of ibogaine on dopamine efflux in response to the administration of
drugs of abuse are described in Section III.E, “Dopamine Efflux”.
6. Acetylcholine
Ibogaine is a nonselective and weak inhibitor of binding to muscarinic receptor
subtypes. Reported affinities are 7.6 and 16 µM and 5.9 and 31 µM, respectively,
for the M1and M2muscarinic receptor subtypes (40,45), with another study
reporting no significant affinity of ibogaine for muscarinic receptors (43).
Functional evidence consistent with a muscarinic cholinergic agonist effect of
ibogaine includes the observations of the elimination of ibogaine-induced EEG
dyssynchrony by atropine in cats (89), decreased heart rate following ibogaine
administration in rats (90), and the attribution of the effect of cholinesterase
inhibition to ibogaine in the older literature (1,91). The affinity of noribogaine for
muscarinic receptors is apparently similar to that of ibogaine (44,45).
Several laboratories have reported that ibogaine produces noncompetitive
functional inhibition of the nicotinic acetylcholine receptor, apparently involving
open channel blockade (46,48-50). As with a number of other channel blockers,
binding studies involving channels associated with nicotinic receptors have been
9
1. ibogaine: a review
limited by the lack of appropriate ligands, and investigations of the affinity of
ibogaine for the nicotinic acetylcholine receptor have mainly involved functional
assays. Utilizing 86Rb+efflux assays, Fryer and Lukas (50) found that ibogaine
inhibited human ganglionic and muscle-type nicotinic acetylcholine receptors
with IC50 values of 1.06 and 22.3 µM, respectively. Badio et al. (48) found that
ibogaine inhibited 22Na+influx through rat ganglionic and human muscle-type
nicotinic acetylcholine receptors with IC50 values of 0.020 µM and 2.0 µM,
respectively. Noribogaine was 75-fold less active than ibogaine in the rat
ganglionic cell assay. In mice, ibogaine at a dose of 10 mg/kg completely blocked
the central antinociceptive nicotinic receptor-mediated response to epibatidine.
Ibogaine has been associated with decreased acetylcholine-stimulated nicotinic
receptor mediated catecholamine release in cultured cells (49) and decreased
dopamine release evoked by nicotine in the NAc of the rat (46,92).
7. Sigma Receptors
Elsewhere in this volume, Bowen discusses ibogaine’s action at the sigma
receptor. The affinity of ibogaine for the sigma2receptor is strong relative to other
known CNS receptors, and the reported range is 0.09 to 1.8 µM (45,60,93,94).
The affinity of ibogaine for the sigma1receptor is reportedly on the order of 2 to
100 times weaker than its affinity for the sigma2receptor (45,60,93,94). The
neurotoxic effects of ibogaine may involve activity at the sigma2receptor, which
reportedly potentiates the neuronal response to NMDA (95).
8. Sodium Channels
The reported affinity of ibogaine for sodium channels ranges from 3.6 to 9 µM
(40,43). There is apparently no experimental evidence regarding the functional
significance of ibogaine’s action at sodium channels.
B. Discrimination Studies
Elsewhere in this volume, Helsley et al. discuss the topic of ibogaine and drug
discrimination. Drug discrimination studies offer a possible approach to the issue
of ibogaine’s mechanism of action and may help resolve the distinction between
ibogaine’s therapeutic and hallucinogenic effects. The 5-HT2A receptor appears to
be a significant, but nonessential, determinant of the ibogaine stimulus (84,96).
The ibogaine stimulus is reportedly generalized to the indolealkylamine
hallucinogen D-lysergic acid diethylamide (LSD) and the phenethylamine
hallucinogen 2,5-dimethoxy-4-ethylamphetamine (DOM), and this general-
ization is abolished by the addition of a 5-HT2A receptor antagonist (96). The
addition of a 5-HT2A receptor antagonist did not attenuate stimulus control of
ibogaine itself in the ibogaine-trained animals, indicating that the 5-HT2A is not
essential to the ibogaine discriminative stimulus. The 5-HT2C receptor, which
10 kenneth r. alper
plays a modulatory role in hallucinogenesis, is also involved, but is not essential
to the ibogaine stimulus, and the 5-HT1A and 5-HT3receptors are apparently not
involved in the ibogaine stimulus (85). The ibogaine discriminative stimulus
reportedly is potentiated by the serotonin reuptake inhibitor fluoxetine (85), and
has an insignificant degree of generalization to the serotonin releaser D-fenflu-
ramine (97).
Ibogaine showed a lack of substitution for phencyclidine (98,99), and
substituted for MK 801 only at high (100 mg/kg) doses in mice (58,61), but not
at lower (10 mg/kg) doses in rats (99,100), suggesting that the NMDA receptor is
not a significant determinant of the ibogaine stimulus. Sigma2, and mu- and
kappa-opioid activity may be involved in the ibogaine discriminative stimulus
(99). A high degree of stimulus generalization is reported between ibogaine and
some of the Harmala alkaloids, a group of hallucinogenic beta-carbolines that are
structurally related to ibogaine (101,102). While the discriminative stimulus for
both the Harmala alkaloids and ibogaine apparently involves the 5-HT2receptor
(84,85,103), it does not appear essential to generalization between ibogaine and
harmaline, as generalization to the harmaline stimulus was unaffected by the
addition of a 5-HT2antagonist in ibogaine-trained animals (84). Ibogaine-trained
rats generalize to noribogaine (100,104), which in one study was more potent
than ibogaine itself in eliciting ibogaine-appropriate responses (100).
C. Effects on Neuropeptides
Both ibogaine and cocaine given in multiple administrations over 4 days to
rats reportedly increase neurotensin-like immunoreactivity (NTLI) in the
striatum, substantia nigra, and NAc (105). However, unlike cocaine, which
increased NTLI in the frontal cortex, ibogaine had no effect on frontal cortical
NTLI. Ibogaine pretreatment prevented the increase of NTLI in striatum and
substantia nigra induced by a single dose of cocaine. Substance P, like NTLI,
was increased in the striatum and substantia nigra after either cocaine or
ibogaine, with an increase in frontal cortex with cocaine and no effect with
ibogaine (106). Ibogaine–induced increases in NTLI or substance P were
blocked by administration of a D1antagonist.
Unlike the NTLI or substance P responses, ibogaine alone had no effect on
dynorphin. However, ibogaine pretreatment dramatically enhanced cocaine-
induced increases in dynorphin, a kappa-opioid agonist (107). The authors
suggested that the increase in dynorphin related to cocaine’s interaction with
ibogaine could result in enhanced kappa-opioid activity. Kappa-opioid agonists
reportedly decrease cocaine intake in animal models (108,109).
11
1. ibogaine: a review
D. Possible Effects on Neuroadaptations Related to
Drug Sensitization or Tolerance
There is some evidence to suggest that ibogaine treatment might result in the
“resetting” or “normalization” of neuroadaptations related to drug sensitization or
tolerance (110 ). Ibogaine pretreatment blocked the expression of sensitization-
induced increases in the release of dopamine in the NAc shell in response to
cocaine in cocaine-sensitized rats (111). The effect of ibogaine on diminished
locomotor activity and dopamine efflux in the NAc in response to morphine is
more evident in animals with prior exposure to morphine (112,113), which is
consistent with a relatively selective effect of ibogaine on neuroadaptations
acquired from drug exposure. Similarly, the observation that ibogaine inhibited
the development of tolerance in morphine-tolerant mice, but had no effect on
morphine nociception in morphine-naïve mice (114 ), suggests a selective effect
on acquired neuroadaptations related to repeated morphine exposure.
Ibogaine appears to have persistent effects not accounted for by a metabolite
with a long biological half-life (29,115). Ibogaine’s action could possibly involve
the opposition or reversal of persistent neuroadaptive changes thought to be
associated with drug tolerance or sensitization. Such an action could be related to
persistent effects on second messengers (72,116). For example, sensitization to
both opiates and cocaine is thought to involve enhanced stimulation of cyclic
AMP (117 ). Ibogaine has been reported to potentiate the inhibition of adenylyl
cyclase by serotonin (72), an effect that would be expected to oppose the
enhanced transduction of cyclic AMP that is reportedly associated with stimulant
sensitization (117 ).
III. Evidence of Efficacy in Animal Models
A. Drug Self-Administration
Evidence for ibogaine’s effectiveness in animal models of addiction includes
observations of reductions in self-administration of morphine or heroin
(29,31,118-120), cocaine (29,31,119,121), and alcohol (122), and reduced
nicotine preference (75). According to some reports, effects of ibogaine on drug
self-administration are apparently persistent. Sershen et al. (121) administered
ibogaine i.p. to mice as two 40 mg/kg dosages 6 hours apart, and found a
diminution of cocaine preference that was still evident after 5 days. Glick et al.
(29,119) noted reductions in cocaine and morphine self-administration that
persisted for at least 2 days and were dose dependent in the range of 2.5 to 80
mg/kg. ibogaine given i.p. The persistence of an effect beyond the first day
12 kenneth r. alper
suggests a specific action of ibogaine on drug intake, as water intake was also
suppressed initially by ibogaine on the first, but not the second day. Cappendijk
and Dzoljic (31) found reductions in cocaine self-administration that persisted for
more than 48 hours in rats treated with ibogaine at a dose of 40 mg/kg i.p., given
as a single administration, or repeatedly on 3 consecutive days or three
consecutive weeks.
In the studies by Glick et al. there was variation between results in individual
rats with some showing persistent decreases in morphine or cocaine intake for
several days or weeks after a single injection and others only after two or three
weekly injections. The authors noted evidence of a continuous range of individual
sensitivity to ibogaine among the experimental animals and that it appeared as if
adjustments of the dosage regimen could produce long-term reductions in drug
intake in most animals (29). Similarly, Cappendijk and Dzoljic (31) found the
largest effects on cocaine self-administration occurred when ibogaine was given
weekly for three consecutive weeks. This result suggests the possibility that the
optimal schedule of ibogaine administration to limit cocaine intake may involve
modification of the single dose regimen which has been used for opioid detoxifi-
cation (32,123).
Dworkin et al. (11 8) found that pretreatment with ibogaine at a dose of 80
mg/kg i.p. diminished the response for heroin and cocaine, and also for food,
suggesting a nonspecific confound. A 40 mg/kg intraperitoneal dose of ibogaine
sharply reduced heroin self-administration in the absence of a significant effect
on food response, although the effect did not persist beyond 24 hours (118 ).
Dworkin et al. cited methodologic factors relating to differences in gender, strain,
and reinforcement schedule to explain the apparent discrepancy between their
results and other studies that reported persistent effects (29,31,119,121).
Noribogaine has also been reported to reduce cocaine and morphine self-
administration (124). The effect of noribogaine on drug self-administration
persisted for 2 days, after the response for water, which was initially suppressed
on the first day, had returned to baseline. Other iboga alkaloids have also been
reported to reduce morphine and cocaine self-administration in rats for a period
of a day or longer following a single i.p dose (119 ). Some of the iboga alkaloids
tested in this study produced tremors, which typically occurred for a period of 2
to 3 hours, and were independent of persistent effects of drug self-administration.
An ibogaine congener, 18-methoxycoronaridine (18-MC) (45), reportedly
reduces in rats the self-administration of cocaine (120), morphine and alcohol
(125), and nicotine preference (75) without any apparent reduction in the
response for water.
B. Acute Opioid Withdrawal
Dzoljic et al. (28) administered ibogaine in a dose range of 4 to 16 µg intra-
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1. ibogaine: a review
cerebroventricularly to rats and observed a dose-dependent attenuation of
naloxone-precipitated withdrawal signs. This same group also found an
attenuation of morphine withdrawal signs in rats with 40 mg/kg ibogaine
administered i.p., and also norharman, an endogenously occurring hallucinogenic
beta-carboline and a structural relative of ibogaine (126). Glick et al. have
reported dose-dependent reduction of the signs of naltrexone-precipitated
morphine withdrawal in rats administered ibogaine at doses of 20, 40, or 80
mg/kg i.p (127) or 18-MC (128) at doses of 20 and 40 mg/kg i.p. Attenuation of
withdrawal signs was reported in morphine-dependent monkeys given 2 or 8
mg/kg ibogaine subcutaneously (129). In their chapter in this volume, Parker and
Siegel report that 40 mg/kg ibogaine administered i.p attenuated naloxone-
precipitated morphine withdrawal in rats, as well as withdrawal-induced place
aversion.
Sharpe and Jaffe (130) reported that ibogaine in dosages ranging between 5
and 40 mg/kg administered subcutaneously failed to attenuate naloxone-precip-
itated withdrawal in rats, although they did find that one sign (grooming) was
reduced, and noted the possible effect of methodological issues such as morphine
exposure and withdrawal procedures, or the route of administration of ibogaine.
Popik et al. (58) and Layer et al. (56) found that ibogaine at doses ranging from
40 to 80 mg/kg i.p. reduced naloxone-precipitated jumping in morphine
dependent mice, although Francés et al. (69) found the opposite effect of 30
mg/kg ibogaine administered i.p. in mice. As pointed out by Popik and Skolnik
(39), the divergent results in morphine dependent mice might relate to ibogaine
having been given prior to the administration of naloxone in the studies by Popik
et al. (58) and Layer et al. (56), whereas ibogaine was administered after
naloxone in the study by Francés et al.
C. Conditioned Place Preference
Parker and Siegel review ibogaine and place preference in this volume.
Ibogaine is reported to prevent the acquisition of place preference when given 24
hours before amphetamine (131) or morphine (132). The effect of ibogaine on
blocking the acquisition of place preference was diminished across multiple
conditioning trials. Ibogaine given after morphine did not apparently attenuate
the expression of previously established morphine place preference (133).
D. Locomotor Activity
Pretreatment with ibogaine and its principal metabolite, noribogaine reportedly
diminishes locomotor activation in response to morphine (74,112,113,124,134-
136). The effect of ibogaine in reducing locomotor activity in response to
morphine is reportedly greater in female than in male rats, probably reflecting the
14 kenneth r. alper
relatively greater bioavailability of ibogaine in females (135). The literature on
cocaine appears to be less consistent, with some reports of decreased locomotor
activation (87,137-139), and others reporting increases (127,137,140,141). This
apparent disparity may be related in part to the species of experimental animal
that was used, as Sershen et al. (137) report increased locomotor activity in
response to cocaine in the rat, with the opposite result in the mouse.
Stereotypy is a methodologic issue that might explain some of the disparate
results regarding ibogaine’s interaction with the locomotor response to cocaine.
Higher doses of stimulants can produce strereotypy, which could decrease the
amount of measured locomotion relative to an animal that is experiencing less
locomotor stimulation at a lower stimulant dose. Thus, the potentiation by
ibogaine of locomotor activity related to cocaine administration can result in less
measured movement in animals experiencing locomotor stimulation to the point
of stereotypy (110 ). Ibogaine pretreatment reportedly potentiates stereotypy in
rats receiving cocaine or methamphetamine (111,142).
E. Dopamine Efflux
Reductions in dopamine efflux in the NAc in response to morphine have been
reported in animals pretreated with ibogaine (113,115,134), noribogaine (124), or
18-MC (120,143). Similarly, reductions in dopamine efflux in the NAc in
response to nicotine have been reported in animals pretreated with ibogaine
(46,92) and 18-MC (42).
As with locomotor stimulation, methodological issues may have played a part
in apparently divergent results regarding ibogaine’s effect on dopamine efflux in
the NAc in response to cocaine or amphetamine, which is reportedly increased as
measured by microdialysis (134), although the opposite result was observed in a
study on cocaine using microvoltammetry (139). Dosage is an additional consid-
eration that might influence ibogaine’s effect on dopamine efflux in the NAc in
response to cocaine, with a larger ibogaine dose reportedly producing an increase
and a smaller dose producing a decrease (144).
Dopamine efflux in response to cocaine may also depend on whether dopamine
measurements are made in the NAc core versus shell. Szumlinski et al. (111)
found that ibogaine pretreatment (given 19 hours earlier) abolished the sensitized
dopamine efflux in response to cocaine in the NAc shell in rats that had been
sensitized by repeated prior exposure to cocaine. The same ibogaine pretreatment
had no apparent effect on dopamine efflux in the NAc shell in response to “acute”
(administered without prior cocaine exposure) cocaine. The authors noted a prior
study in their laboratory that found a potentiation by ibogaine pretreatment of
dopamine efflux in response to acute cocaine in which the position of the
recording probe spanned both the core and shell regions of the NAc (134). These
results indicate the possibility of a differential effect of ibogaine on dopamine
15
1. ibogaine: a review
efflux in response to cocaine between the NAc shell, which is thought to play a
relatively greater role in the motivational aspects of drugs of abuse, and the NAc
core, which, in turn, is thought to play a relatively greater role in motor behavior
(145). The authors suggested that the effect of ibogaine on reduced cocaine self-
administration may be mediated by the observed reduction in dopamine efflux in
response to cocaine in the NAc shell in cocaine-sensitized animals (111). On the
other hand, the enhancement by ibogaine preatreatment of locomotor activity
seen in response to acute or chronic cocaine administration may be mediated by
increased dopamine efflux in the NAc core. The observed increase in dopamine
efflux with ibogaine pretreatment in the NAc core in response to acute cocaine
(134) is consistent with such a formulation, although this group has yet to report
on the effect in cocaine-sensitized animals.
Ibogaine and 18-MC reportedly decrease dopamine release evoked by nicotine
in the NAc of the rat (46,92). In the study by Benwell et al. (46), the decreased
NAc dopamine release following ibogaine was independent of any change in
locomotor activity, which was viewed as notable given the usual association
between NAc dopamine efflux and locomotor activity in response to nicotine.
The authors cited previous work in which a similar dissociation between NAc
dopamine efflux and locomotor activity in response to nicotine was produced by
treatment with NMDA antagonists, and they suggested that their findings might
be related to ibogaine’s NMDA antagonist activity.
IV. Evidence of Efficacy and Subjective Effects in Humans
A. Evidence Of Efficacy
1. Acute Opioid Withdrawal
One line of clinical evidence suggesting ibogaine’s possible efficacy are the
accounts of the addicts themselves, whose demand has led to the existence of an
“informal” treatment network in Europe and the United States. Opioid
dependence is the most common indication for which addicts have sought
ibogaine treatment, which has been typically administered as a single dose.
Common reported features of case reports describing ibogaine treatment
(35,36,146-149) are reductions in drug craving and opiate withdrawal signs and
symptoms within 1 to 2 hours, and sustained, complete resolution of the opioid
withdrawal syndrome after the ingestion of ibogaine. These case studies appear
consistent with general descriptions of ibogaine treatment (33,34,150).
Alper et al. (32) summarized 33 cases treated for the indication of opioid
detoxification in nonmedical settings under open label conditions. These cases
16 kenneth r. alper
are a subset of those presented at the NIDA Ibogaine Review Meeting held in
March, 1995 (151). A focus on acute opioid withdrawal may offset some of the
methodological limitations of the informal treatment context because the acute
opioid withdrawal syndrome is a clinically robust phenomenon that occurs within
a relatively limited time frame and yields reasonably clear outcome measures.
Despite the unconventional setting and the lack of structured clinical rating
instruments, the lay “treatment guides” who reported on the case series might
reasonably be expected to be able to assess the presence or absence of the
relatively clinically obvious and unambiguous features of opioid withdrawal.
The subjects in this series of cases reported an average daily use of heroin of
0.64 ± 0.50 g, primarily by the intravenous route, and received an average dose
of ibogaine of 19.3 ± 6.9 mg/kg (range of 6 to 29 mg/kg). Resolution of the signs
of opioid withdrawal without further drug seeking behavior was observed in 25
patients. Other outcomes included drug seeking behavior without withdrawal
signs (four patients), drug abstinence with attenuated withdrawal signs (two
patients), drug seeking behavior with continued withdrawal signs (one patient),
and one fatality, possibly involving surreptitious heroin use (see Section VI,
“Safety”). The reported effectiveness of ibogaine in this series suggests the need
for a systematic investigation in a conventional clinical research setting.
In their chapter in this volume, Mash et al. report having treated more than 150
subjects for substance dependence in a clinic located in St. Kitts, West Indies. A
subset of 32 of these subjects was treated with a fixed dose of ibogaine of 800 mg
for the indication of opioid withdrawal. Physician ratings utilizing structured
instruments for signs and symptoms of opioid withdrawal indicated resolution of
withdrawal signs and symptoms at time points corresponding to 12 hours
following ibogaine administration and 24 hours after the last use of opiates, and
at 24 hours following ibogaine administration and 36 hours after the last use of
opiates. The resolution of withdrawal signs and symptoms was sustained during
subsequent observations over an interval of approximately one week following
ibogaine administration. Reductions of measures of depression and craving
remained significantly reduced one month after treatment (123). The authors
noted that ibogaine appeared to be equally efficacious in achieving detoxification
from either methadone or heroin. The reported efficacy of ibogaine for the opioid
withdrawal syndrome observed in the St. Kitts facility appears to confirm the
earlier impressions of the case study literature (32-36,146-150).
2. Long-Term Outcomes
There is very little data regarding the long-term outcomes in patients treated
with ibogaine. Lotsof (151) presented a summary of 41 individuals treated
between 1962 and 1993 at the NIDA Ibogaine Review Meeting held in March
1995. The data consisted of self-reports obtained retrospectively, which are
essentially anecdotal, but apparently represent the only formal presentation of a
17
1. ibogaine: a review
systematic attempt to determine long-term outcomes in patients treated with
ibogaine. Thirty-eight of the 41 individuals presented in the summary reported
some opioid use, with approximately 10 of these apparently additionally
dependent on other drugs, mainly cocaine, alcohol, or sedative-hypnotics. The
use of tobacco or cannabis was not apparently assessed. Across the sample of 41
individuals, nine individuals were treated twice and one was treated three times
for a total of 52 treatments. The interval of time following treatment was recorded
for which patients reported cessation of use of the drug or drugs on which they
were dependent. Fifteen (29%) of the treatments were reportedly followed by
cessation drug use for less than 2 months, 15 (29%) for at least 2 months and less
than 6 months, 7 (13%) for at least 6 months and less than one year, 10 (19%) for
a period of greater than one year, and in 5 (10%) outcomes could not be
determined.
B. Subjective Effects
There appear to be common elements to experiences generally described by
patients treated with ibogaine. The “stages” of the subjective ibogaine experience
presented below are a composite derived by the author from interviews with
patients and treatment guides, and general descriptions and case studies provided
by the literature (33-35,146,150). Ibogaine has been typically given in a non-
hospital setting as a single dose in the morning. Vomiting is reportedly common
and usually occurred relatively suddenly as a single episode in the first several
hours of treatment. Patients generally lie still in a quiet darkened room
throughout their treatment, a practice that is possibly related to the cerebellar
effects of ibogaine, and because vomiting tends to be more frequent with
movement. Patients later in treatment often experience muscle soreness, possibly
due to reduced motor activity earlier in treatment, that resolves with motion,
stretching, or massage.
1. Acute
The onset of this phase is within 1 to 3 hours of ingestion, with a duration on
the order of 4 to 8 hours. The predominant reported experiences appear to involve
a panoramic readout of long-term memory (152), particularly in the visual
modality, and “visions” or “waking dream” states featuring archetypal
experiences such as contact with transcendent beings, passage along a lengthy
path, or floating. Descriptions of this state appear more consistent with the
experience of dreams than of hallucinations. Informants appear to emphasize the
experience of being placed in, entering, and exiting entire visual landscapes,
rather than the intrusion of visual or auditory hallucinations on an otherwise
continuous waking experience of reality. Ibogaine-related visual experiences are
reported to be strongly associated with eye closure and suppressed by eye
18 kenneth r. alper
opening. The term “oneiric” (Greek, oneiros, dream) has been preferred to the
term “hallucinogenic” in describing the subjective experience of the acute state.
Not all subjects experience visual phenomena from ibogaine, which may be
related to dose, bioavailability, and interindividual variation.
2. Evaluative
The onset of this phase is approximately 4 to 8 hours after ingestion, with a
duration on the order of 8 to 20 hours. The volume of material recalled slows. The
emotional tone of this phase is generally described as neutral and reflective.
Attention is still focused on inner subjective experience rather than the external
environment, and it is directed at evaluating the experiences of the acute phase.
Patients in this and the acute phase above are apparently easily distracted and
annoyed by ambient environmental stimuli and prefer as little environmental
sensory stimulation as possible in order to maintain an attentional focus on inner
experience.
3. Residual Stimulation
The onset of this phase is approximately 12 to 24 hours after ingestion, with a
duration in the range of 24 to 72 hours or longer. There is a reported return of
normal allocation of attention to the external environment. The intensity of the
subjective psychoactive experience lessens, with mild residual subjective arousal
or vigilance. Some patients report reduced need for sleep for several days to
weeks following treatment. It is not clear to what extent such reports might reflect
a persistent effect of ibogaine on sleep or a dyssomnia due to another cause.
V. Pharmacokinetics
A. Absorption
Jeffcoat et al. (153) administered single oral doses of ibogaine of 5 mg/kg and
50 mg/kg to rats, and estimated oral bioavailabilities of 16 and 71% at the two
dosages, respectively, in females, and 7 and 43% in males. The dose-dependent
bioavailability was interpreted as suggesting that ibogaine absorption, and/or first
pass elimination, is nonlinear, and the greater bioavailability in females was
viewed as consistent with gender-related differences in absorption kinetics. Pearl
et al. (135) administered ibogaine at a dose of 40 mg/kg i.p. and found whole
brain levels at 1, 5, and 19 hours post-administration of 10, 1, and 0.7 µM in
female rats, and 6, 0.9, and 0.2 µM in male rats, respectively. In the same study,
brain levels of noribogaine at 1, 5, and 19 hours post-administration were 20, 10,
19
1. ibogaine: a review
and 0.8 µM in female rats, and 13, 7, and 0.1 µM and male rats respectively. In
addition to gender differences in bioavailability, the data also provide evidence
for the pharmacologic relevance of micromolar activities of ibogaine and
noribogaine measured in vitro (40,44).
Upton (154) reported on observations in rats given ibogaine in the form of oral
suspension, oral solution, or via IV or intraperitoneal routes, and also reviewed
data obtained in beagle dogs, cynomologous monkeys, and human subjects.
Absorption of the oral suspension in rats was noted to be variable and incomplete.
As in the study cited above by Jeffcoat (153), peak levels and bioavailability were
greater in female than in male rats.
B. Distribution
Hough et al. (51) administered 40 mg/kg ibogaine by the intraperitoneal and
subcutaneous routes and evaluated its distribution in plasma, brain, kidney, liver,
and fat at 1 and 12 hours post-administration. Ibogaine levels were higher
following subcutaneous versus intraperitoneal administration, suggesting a
substantial “first pass” effect involving hepatic extraction. The results were
consistent with the highly lipophilic nature of ibogaine; ibogaine concentrations
at 1 hour postadministration were 100 times greater in fat, and 30 times greater
in brain, than in plasma. These authors suggested that the prolonged actions of
ibogaine could relate to adipose tissue serving as a reservoir with release and
metabolism to noribogaine over an extended period of time (51). The apparently
greater levels of ibogaine in whole blood versus plasma suggests the possibility
that platelets might constitute a depot in which ibogaine is sequestered (42). If
there is conversion of ibogaine to noribogaine in the brain, then the significantly
greater polarity of noribogaine relative to ibogaine could prolong the presence of
the more polar metabolite in the CNS after conversion from ibogaine (42).
C. Metabolism
The major metabolite of ibogaine, noribogaine, is formed through demethy-
lation, apparently via the cytochrome P-450 2D6 (CYP2D6) isoform (155).
Consistent with first pass metabolism of the parent drug, noribogaine is
reportedly detectable in brain tissue within 15 minutes after oral administration
of 50 mg/kg ibogaine (44). Noribogaine is itself pharmacologically active and is
discussed in this volume by Baumann et al.
In pooled human liver microsomes, Pablo et al. identified two kinetically
distinguishable ibogaine O-demethylase activities which corresponded, respec-
tively, to high and low values of the apparent Michaelis constant (Kmapp) (155).
The low Kmapp ibogaine O-demethylase activity was attributable to CYP2D6 and
accounted for greater than 95% of the total intrinsic clearance in pooled human
20 kenneth r. alper
liver microsomes. The authors noted that the apparent involvement of the
CYP2D6 suggests possible human pharmacogenetic differences in the
metabolism of ibogaine. “Poor metabolizers” who lack a copy of the CYP2D6
gene (156) would be expected to have relatively less CYP2D6-catalyzed activity
to metabolize ibogaine to noribogaine. Consistent with such an expectation, a
subject identified as a phenotypic CYP2D6 poor metabolizer possessed only the
high Kmapp ibogaine O-demethylase activity, which had accounted for only a
small fraction of the intrinsic clearance. In another study, analysis of ibogaine and
noribogaine levels in human subjects yielded a distribution interpreted as
indicating three groups of rapid, intermediate, and poor metabolizers (157), a
pattern consistent with the observed pharmacogenetic polymorphism of CYP2D6
in human populations (156).
D. Excretion
Ibogaine has an estimated half-life on the order of 1 hour in rodents (158), and
7.5 hours in man (Mash et al., this volume). Ibogaine and its principal metabolite,
noribogaine, are excreted via the renal and gastrointestinal tracts. In rats, Jeffcoat
et al. (153) noted 60 to 70% elimination in urine and feces within 24 hours, and
Hough et al. (51) found plasma and tissue levels to be 10 to 20-fold lower at 12
hours versus 1 hour post dose.
Upton and colleagues (154) cited several pharmacokinetic issues of potential
concern based on their analysis of data obtained from rats. These include
evidence for presystemic clearance potentially resulting in low bioavailability
and interpatient variability, and saturable first pass clearance, which could also
generate intrapatient variability. The possibility of saturable systemic clearance
was also noted. Mash et al. (36) suggested the possibility of species or strain
differences in ibogaine metabolism and clearance rates and cited the rapid
elimination of ibogaine from the blood of primates, as opposed to rats or humans,
as an example.
In human subjects, 90% of a 20 mg/kg dose of ibogaine was reportedly
eliminated within 24 hours (36). Noribogaine is apparently eliminated signifi-
cantly more slowly than ibogaine, and observations in human subjects indicate
persistently high levels of noribogaine at 24 hours (36,79,123, Mash et al. in this
volume). The sequestration and slow release from tissues of ibogaine or
noribogaine and the slow elimination of noribogaine have been suggested to
account for the apparently persistent effects of ibogaine.
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1. ibogaine: a review
VI. Safety
A. Neurotoxicity
1. Neuropathology
Multiple laboratories have reported on the degeneration of cerebellar Purkinje
cells in rats given ibogaine at a dose of 100 mg/kg i.p. (159,160). However, the
available evidence suggests that the neurotoxic effects of ibogaine may occur at
levels higher than those observed to have effects on opioid withdrawal and self-
administration. Molinari et al. (161) found no evidence of cerebellar Purkinje cell
degeneration with 40 mg/kg i.p. administered as a single dose, which is reported
to reduce morphine or cocaine self-administration or morphine withdrawal in rats
(29,119,126,161). Xu et al. (162) evaluated biomarkers of cerebellar
neurotoxicity in rats treated with single doses of ibogaine of 25, 50, 75, and 100
mg/kg i.p. The biomarkers used in this study included the specific labeling of
degenerating neurons with silver, and Purkinje neurons with antisera to calbindin.
Astrocytes were identified with antisera to glial fibrillary acidic protein (GFAP),
a marker of reactive gliosis, a general response of astrocytes to CNS injury. The
25 mg/kg dosage was found to correspond to a no-observable-adverse-effect-
level (NOAEL). Helsley et al. (102) treated rats with 10 mg/kg ibogaine every
other day for 60 days and observed no evidence of neurotoxicity.
Regarding the question of neurotoxicity in brain areas outside the cerebellum,
O’Hearn and Molliver (163) have stated, “Evidence of neuronal injury following
ibogaine administration in rats appears to be almost entirely limited to the
cerebellum.” While the cerebellum appears to be the brain region most vulnerable
to neurotoxic effects of ibogaine, some research has addressed the issue of
neurotoxicity in other brain regions. O’Callaghan et al. (164) examined GFAP in
male and female rats exposed to either an “acute” regimen of ibogaine
administered at doses of 50, 100, or 150 mg/kg i.p. daily for 3 days or a “chronic”
regimen of daily oral administration of 25, 75, or 150 mg/kg for 14 days. The
acute i.p. regimen produced elevations of GFAP in animals of either gender that
were not restricted to the cerebellum, and were observed in the cerebellum and
hippocampus at the 50 mg/kg dosage level, and in the cortex, hippocampus,
olfactory bulb, brain stem, and striatum at the 100 mg/kg level. The effect of the
acute ibogaine regimen on GFAP was no longer evident at 14 days with either
dosage in male rats, and was restricted to the cerebellum with the 100 mg/kg dose
in female rats. GFAPlevels were examined at 17 days after the completion of the
chronic dosing regimen. No elevations of GFAP were found in any of the brain
regions examined at any of the dosages administered utilizing the chronic
regimen in males, and elevations of GFAP were found only in females, which
were restricted to the hippocampus with the 25 mg/kg dosage regimen and were
22 kenneth r. alper
present in the hippocampus, olfactory bulb, striatum, and brain stem with the 150
mg/kg dosage regimen.
O’Hearn et al. (159) found GFAP elevations in the cerebellum only, and not the
forebrain of male rats administered 100 mg/kg doses i.p on up to 3 consecutive
days. Elevations of GFAP are relatively sensitive, but not specific to, neuronal
degeneration (162). Using a silver degeneration-selective stain as a histologic
marker of neurodegeneration, Scallet et al. (165) examined diverse brain regions
in rats and mice treated with single 100 mg/kg doses of ibogaine administered i.p.
and found evidence of neurodegeneration only in the cerebellum in rats, whereas
mice showed no evidence of neurodegeneration. In rats that received a dose of
ibogaine of 100 mg/kg i.p., neuronal degeneration was confined to the cerebellum
as revealed by staining with Fluoro-Jade, a recently developed sensitive and
definitive marker of neuronal degeneration (166,167).
Sensitivity to ibogaine neurotoxicity appears to vary significantly between
species. The monkey appears to be less sensitive to potential ibogaine
neurotoxicity than the rat (36). Mash et al. observed no evidence of neurotoxicity
in monkeys treated for 5 days with repeated oral doses of ibogaine of 5 to 25
mg/kg, or subcutaneously administered doses of 100 mg/kg (36). Another species
difference in sensitivity is the mouse, which unlike the rat shows no evidence of
cerebellar degeneration at a 100 mg/kg i.p. dose of ibogaine (165).
2. Mechanisms of Neurotoxicity
Ibogaine’s cerebellar toxicity could be related to excitatory effects mediated by
sigma2receptors in the olivocerebellar projection, which sends glutaminergic
excitatory input to cerebellar Purkinje cells, whose synaptic redundancy makes
them particularly vulnerable to excitotoxic injury (160). Sigma2agonists are
reported to potentiate the neuronal response to NMDA (95), and potentiation of
glutamatergic responses at Purkinje cells might lead to the observed
neurotoxicity. Sigma2agonists have also been shown to induce apoptosis, and
activation of sigma2receptors by ibogaine results in direct neurotoxicity via
induction of apoptosis in in vitro cell culture systems (168,169). Elsewhere in this
volume, Bowen discusses the effects of iboga alkaloids at sigma2receptors. It is
possible therefore that ibogaine’s neurotoxic effect on the highly sensitive
Purkinje neurons is the result of combined direct neurotoxicity and excitotoxicity
due to the enhancement of glutamatergic activity, both effects being mediated by
sigma2receptors. The agonist activity of ibogaine at the sigma2receptor might
explain the apparent paradox of ibogaine-induced excitotoxicity, despite its
properties as an NMDA antagonist (42). The neurotoxic effects of iboga alkaloids
can apparently be dissociated from their putative effects on addiction, since
sigma2receptors appear not to be involved in the suppression of drug self-
administration. 18-MC, an ibogaine congener with relatively much less sigma2
affinity, reportedly produces effects similar to ibogaine on morphine and cocaine
23
1. ibogaine: a review
administration in rats, but has shown no evidence of neurotoxicity, even at high
dosages (42,75,120).
Ibogaine’s NMDA antagonist activity has been cited as a rationale for a patent
for its use as a neuroprotective agent to minimize excitotoxic damage in stroke
and anoxic brain injury (170). In methamphetamine-treated mice, ibogaine is
reported to protect against hyperthermia and the induction of heat shock protein,
which are possible mediators of methamphetamine neurotoxicity (171). Binienda
et al. in this volume report an accentuation of delta amplitude in ibogaine
pretreated animals given cocaine, and they suggest a “paradoxical” proconvulsant
effect resulting from the interaction of cocaine and ibogaine, similar to
interactions reported between cocaine and other noncompetitive NMDA
antagonists. However, ibogaine is reported to protect against convulsions
produced by electroshock (61), or the administration of NMDA (55). Luciano et
al. (148) did not observe EEG abnormalities in five human subjects during
treatment with ibogaine in the dosage range of 20 to 25 mg/kg. There is
apparently no reported human data on possible differences between the pre- and
post-ibogaine treatment EEG, or effects persisting into extended periods of time
after treatment.
3. Tremor
Ibogaine has been noted to produce tremor at dosages of 10 mg/kg i.p. in rats
(172) and 12 mg/kg s.c. in mice (173). Glick et al. (119 ) evaluated ibogaine and
several other iboga alkaloids and found that their effects on drug self-adminis-
tration and tendency to produce tremor were independent from one another.
Studies of structure-activity relationships of the iboga alkaloids indicate that the
tendency to cause tremor is enhanced by the presence of a methoxy group at
position 10 or 11 and is diminished or eliminated by the presence of a
carbomethoxy group at position 16 (173,174). Accordingly, tremors were not
produced in rats administered noribogaine, which differs from ibogaine with
respect to the absence of a methoxy group at position 10, at a dosage of 40 mg/kg
i.p. (124). Likewise, tremors were not observed in rats administered a dosage of
18-MC as high as 100 mg/kg. 18-MC differs from ibogaine with respect to the
absence of a methoxy group at position 10 and the presence of a carbomethoxy
group at position 16 (120).
4. Observations in Humans
Concern over possible neurotoxicity led Mash et al. to quantitatively
investigate ibogaine’s effects on postural stability, body tremor, and appendicular
tremor in humans (36). In U.S. FDA safety trials, nine subjects receiving 1 and 2
mg/kg of ibogaine showed only a statistically insignificant increase in body sway
6 hours after taking ibogaine. Ten patients evaluated 5 to 7 days after receiving
doses of ibogaine ranging from 10 to 30 mg/kg showed no evidence of
24 kenneth r. alper
abnormality on quantitative measures of static or dynamic posturography or hand
accelometry, or on clinical neurologic exam.
A woman died in the United States in 1994 who had been previously treated
with ibogaine 25 days earlier (36). This woman had undergone four separate
treatments with ibogaine in dosages ranging from 10 to 30 mg/kg in the 15
months prior to her death. The cause of death was concluded to have been a
mesenteric arterial thrombosis related to chronic cellulitis, and a role for ibogaine
in causing the fatality was not suspected. Of interest with regard to concerns over
potential neurotoxicity, was the absence of any neuropathological abnormality
not associated with chronic IV drug use. Neuropathological examination revealed
only slight medullary neuroaxonal dystrophy and an old focal meningeal fibrosis,
which were explainable on the basis of chronic IV drug use (36). There was no
evidence of cytopathology or neurodegenerative changes in the cerebellum or any
other brain area, nor was there evidence of astrocytosis or microglial activation.
B. Cardiovascular Effects
Glick et al. (45) found no changes in resting heart rate or blood pressure in rats
at the dose of 40 mg/kg of ibogaine, which was often used in that laboratory in
drug withdrawal or self-administration studies. Higher doses of ibogaine (100
and 200 mg/kg) decreased the heart rate without an effect on blood pressure, and
18-MC had no apparent effect on heart rate or blood pressure at any of the above
doses. Binieda et al. (90) found a significantly decreased heart rate in rats given
50 mg/kg of ibogaine.
Mash et al. (175) reported on intensive cardiac monitoring in 39 human
subjects dependent on cocaine and/or heroin who received fixed doses of
ibogaine of 500, 600, 800, or 1000 mg. Six subjects exhibited some significant
decrease of resting pulse rate relative to baseline, one of whom evidenced a
significant decrease in blood pressure, which was attributed to a transient
vasovagal response. Monitoring revealed no evidence of EKG abnormalities
appearing or intensifying during ibogaine treatment. No significant adverse
events were seen under the study conditions, and it was concluded that the single
dose of ibogaine was apparently well tolerated. In their chapter in this volume,
Mash et al. comment further that random regression of vital signs showed no
changes across time or by dosage in opiate-dependent subjects. They did however
observe the occurrence of a hypotensive response to ibogaine in some cocaine-
dependent subjects, which was responsive to volume repletion.
C. Fatalities
The LD50 of ibogaine is reportedly 145 mg/kg i.p. and 327 mg/kg intragas-
trically in the rat, and 175 mg/kg i.p. in the mouse (158).
25
1. ibogaine: a review
In June 1990, a 44 year-old woman died in France approximately 4 hours after
receiving a dose of ibogaine of about 4.5 mg/kg. The cause of death was
concluded to have been acute heart failure in an autopsy carried out at the
Forensic-Medical Institute in Zurich (176). Autopsy revealed evidence of a prior
myocardial infarction of the left ventricle, severe atherosclerotic changes, and 70
to 80% stenosis of all three major coronary artery branches. This patient had a
history of hypertension, and inverted T waves were noted on EKG three months
prior to the patient’s death. The autopsy report concluded that the patients
preexisting heart disease was likely to have caused the patient’s death, and it
specifically excluded the possibility of a direct toxic effect of ibogaine. The report
acknowledged the possibility that an interaction between ibogaine and the
patient’s preexisting heart condition could have been a contributing factor in the
fatal outcome.
The autopsy report, which included information obtained from the patient’s
family physician, and the psychiatrist who administered ibogaine, makes
reference to the possibility that the patient might have taken other drugs. The
autopsy report noted the presence of amphetamine in the enzyme immunocyto-
chemical (EMIT) assay of a dialysate of the kidney tissue (urine was reported not
to be obtainable). This finding, however, was regarded as artifactual and possibly
attributable to a false positive EMIT result due to the presence of phenylethy-
lamine.
A fatality occurred during a heroin detoxification treatment of a 24-year-old
female in the Netherlands in June 1993. This incident was a significant factor in
the NIDA decision not to fund a clinical trial of ibogaine in 1995. The patient
received a total ibogaine dose of 29 mg/kg and suffered a respiratory arrest and
died 19 hours after the start of the treatment. Forensic pathological examination
revealed no definitive conclusion regarding the probable cause of death (177) and
cited the general lack of information correlating ibogaine concentrations with
possible toxic effects in humans. The high levels of noribogaine found in the
deceased patient were possibly consistent with saturation of elimination kinetics.
However, the higher levels of noribogaine in heart, relative to femoral blood, also
suggested significant postmortem redistribution of noribogaine. The potential
artifact associated with a high volume of distribution and postmortem release of
drug previously sequestered in tissue (51,139,158) limits the interpretability of
postmortem levels of noribogaine.
Some evidence suggested the possibility of surreptitious opioid use in this
case, which was noted in the Dutch inquiry (178) and which is another source of
uncertainty in this fatality. There is evidence suggesting that the interaction of
opioids and ibogaine potentiates opioid toxicity (68,179). Analysis of gastric
contents for heroin or morphine, which might have confirmed recent heroin
smoking, and analysis of blood for 6-monoacetyl morphine, a heroin metabolite
whose presence indicates recent use (180), were not performed. This incident
26 kenneth r. alper
underscores the need for the security and medical supervision available in a
conventional medical setting, and for completion of dose escalation studies to
allow systematic collection of pharmacokinetic and safety data.
In London, in January 2000, a 40-year-old heroin addict died after having
allegedly taken 5 g of iboga alkaloid extract 40 hours prior to his death (38, see
the chapter by Alper et al. in this volume). The extract was said to have contained
approximately five times the alkaloid content of the dried rootbark. The official
British inquest regarding this matter is still in progress as of the time of the
writing of this book.
D. Abuse Liability
The available evidence does not appear to suggest that ibogaine has significant
potential for abuse. The 5-HT2A receptor, the primary mediator of responding for
LSD and other commonly abused drugs classified as “hallucinogenic” or
“psychedelic,” does not appear to be essential to discriminability of the ibogaine
stimulus (84,96). Ibogaine is reportedly neither rewarding or aversive in the
conditioned place preference paradigm (132). Rats given either 10 or 40 mg/kg
ibogaine daily for 6 consecutive days did not show withdrawal signs (129).
Animals do not self-administer 18-MC, an ibogaine analog, in paradigms in
which they self-administer drugs of abuse (45). None of the consultants to NIDA
in the 1995 Ibogaine Review Meeting identified the possible abuse of ibogaine as
a potential safety concern.
VII. Learning, Memory, and Neurophysiology
A. Learning, Memory, and Addiction
Drug abusers may be viewed as having a disorder involving excess attribution
of salience to drugs and drug-related stimuli (181), which suggests the possibility
of a role of processes subserving learning and memory in the acquisition of the
pathological motivational focus in addiction (182-185). Learning, in the most
general sense, can be viewed as the modification of future brain activity, of which
thought, motivation, consciousness, or sensory experience are emergent
properties, on the basis of prior experience. This broad definition subsumes
everything from social behavior to learning to read, to the neuroadaptations of
drug tolerance and dependence.
Addiction can be argued to involve the pathological acquisition or “learning”
of associations of drug related stimuli with motivational states corresponding to
27
1. ibogaine: a review
valuation and importance (181,183,184). The pathological learning of addiction
differs from that of normal learning in at least two important respects. First, the
acquisition of drug salience in addiction does not involve learned associations
between drug-related external cues or internal representations, and the experience
of external events as they actually occur. Instead, the “imprinting” or “stamping
in” of drug incentives appears to involve alterations of neural plasticity in
processes that subserve motivation, memory and learning, resulting in neural
behavior that to a significant extent has escaped the constraint of validation by
experience with external reality (183-186). Dopamine and glutamate
transmission are thought to be involved in the modulation of neural plasticity of
both normal learning and the neuroadaptations of drug salience (184). Second,
drug-related “learning” does not apparently habituate (184). Unlike normal
learning, the drug stimulus appears to be experienced as perpetually novel and
continues to command attention and be attributed with salience unattenuated by
habituation (53,182).
B. Effects of Ibogaine on Learning and Memory
Ibogaine appears to have significant effects on brain events involved in
learning and the encoding of drug salience. Ibogaine interacts significantly with
the NMDA receptor (39,58,179), which is involved in long term potentiation
(LTP), a process thought to be important in neural plasticity, memory, and
learning (182,184,187). Experiences apparently involving memory, such as
panoramic recall, are prominent in descriptions by individuals who have taken
ibogaine (14).
The observation of an effect of ibogaine on the expression of behavioral
sensitization to amphetamine, but not a conditioned place preference (188), raises
the interesting possibility of a relatively selective effect of ibogaine on the
pathological encoding of drug salience, distinguished from learning involving
non-drug incentives. Ibogaine reportedly attenuates the acquisition of place
preference for morphine or amphetamine (131,132). A general effect of
interference with learning has been suggested (189), but studies on spatial
learning show an actual enhancement by ibogaine (102,190). Consistent with a
selective effect on neuroadaptations acquired from drug exposure are ibogaine’s
effects on locomotor activity and dopamine efflux in the NAc, which are
relatively more evident in animals with prior experience with morphine (112,113)
or cocaine (111).
C. Ibogaine and the EEG
Studies of animals treated acutely with ibogaine report a desynchronized EEG
with fast low amplitude activity, a state described as “activated” or “aroused”
28 kenneth r. alper
(89,90,191). Binienda et al. (90) noted a decline in delta amplitude and
interpreted this as consistent with activation of dopaminergic receptors. However,
observations on the interaction of atropine and ibogaine with respect to the EEG
suggest the involvement of ascending cholinergic input. Depoortere (191) found
that ibogaine enhanced an atropine-sensitive theta frequency EEG rhythm in rats.
Schneider and Sigg (89) observed a shift toward high-frequency low-voltage
EEG activity following the administration of ibogaine to cats, and they noted that
this effect was blocked by the administration of atropine. Luciano et al. (148)
observed no changes in the visually evaluated EEG in humans administered 20 to
25 mg/kg ibogaine.
D. Goutarel’s Hypothesis
The French chemist Robert Goutarel (14) hypothesized that ibogaine treatment
involves a state with functional aspects shared by the brain states of REM sleep,
with important effects on learning and memory. During the REM state, there is
believed to be reconsolidation of learned information in a state of heightened
neural plasticity, with the reprocessing of previously learned information and the
formation of new associations (192,193). Goutarel suggested that a REM-like
state may be induced by ibogaine, which corresponds to a window of heightened
neural plasticity, during which there may be weakening of the pathological
linkages between cues and representations of the drug incentive and the motiva-
tional states with which they have become paired (14). Analogous to the
reconsolidation of learned information that is thought to occur during the REM
state (192,193), Goutarel theorized that the pathological learning of addiction was
modified during ibogaine treatment. He appears to have based his theoretical
formulation mainly on reports of the phenomenological experiences of awake
ibogaine-treated subjects that share features in common with dreams. Goutarel’s
hypothesis is speculative, but nonetheless has an interesting apparent consistency
with the literature on the relationship of learning and addiction and the
physiologic function of the REM EEG state with regard to the consolidation of
learned information.
There is some evidence that may be viewed as consistent with Goutarel’s
hypothesis. Goutarel’s belief in a relationship of the ibogaine-treated EEG state
to that of REM is supported by studies in animals treated with ibogaine that report
an apparently activated or desynchronized EEG state consistent with arousal,
vigilance, or REM sleep (90,191). The observation that ibogaine enhanced an
atropine-sensitive theta frequency rhythm (191) suggests the possible
involvement of ascending cholinergic input, which is an essential determinant of
EEG desynchronization during REM sleep (192). The possible reconsolidation of
learned information due to heightened plasticity during both the REM and
ibogaine-induced desynchronized EEG states is suggested by the observation that
29
1. ibogaine: a review
EEG dyssynchrony is associated with an increased facilitation of Hebbian
covariance (194), which is believed to be an important determinant of the neural
plasticity involved in consolidation of learning and memory. Also, with regard to
a possible analogy of the REM and ibogaine induced brain states, some ibogaine
treatment guides have anecdotally mentioned that they have observed REM-like
eye movements in awake patients during treatments (195,196).
VIII. Anthropological and Sociological Perspectives
As discussed in various aspects by this volume by the Fernandezes, Frenken,
and Lotsof and Alexander, ibogaine’s use appears to involve distinctive
interactions of psychopharmacologic effects with set and setting in both the
subcultures of the United States and Europe, and the centuries older, sacramental
context of the use of iboga in Bwiti, the religious movement in West Central
Africa. In the Bwiti religious subculture, and arguably to some extent in the
European ibogaine subculture, there is the common attribute of a group of
initiates that seek to facilitate healing through the affiliation of the collective with
the individual. In both the African and U.S./European contexts, the ibogaine
experience has been attributed to serving the objective of facilitating personal
growth and change. Use of ibogaine in both contexts has been criticized as
involving the use of an “addictive” or “hallucinogenic” agent, and it appears to
some extent to involve the formation of a subculture among individuals
confronted with marginal social circumstances such as colonialism, or the state of
addiction (197-199, see also Fernandez and Fernandez in this volume).
Galanter (200) identifies three important psychological features that he regards
as descriptive of the process of charismatic groups or zealous self-help
movements such as 12-step programs that appear to also be relevant to Bwiti.
These three processes are group cohesiveness, shared belief, and altered
consciousness, such as that of religious ecstasy or insight to which the group can
attribute a new construction of reality in their life. An understanding of these
powerful behavioral influences could be useful in optimizing the clinical milieu
and interpersonal dynamics of present conventional treatment settings, or of
future treatment settings, if ibogaine or a congener should receive official
approval.
The application of ethnographic techniques to the analysis of the phenomeno-
logical features of the acute treatment experience could be informative from a
neuropsychiatric, as well as from a cultural perspective. For example, similar
subjective phenomena are frequently described in both ibogaine treatment and
near death experiences (NDEs) (14,152,199,201) such as panoramic memory;
30 kenneth r. alper
calm, detached emotional tone; specific experiences, such as passage along a long
path or floating; “visions” or “waking dream” states featuring archetypal
experiences such as contact with transcendent beings; and the frequent attribution
of transcendent significance to the experience. Such shared features between
ibogaine and NDEs suggest a common transcultural phenomenology of
transcendent or religious experience or, alternatively, the possibility of a similar
subjective experience due to the influence of a common underlying neurobio-
logical mechanism such as NMDA transmission (202).
IX. Economic and Political Perspectives
A. Economic Incentives and the Development of Ibogaine
The academic research community working in the public sector has a crucial
role in studying ibogaine as a paradigm for the development of new treatment
approaches. The strategy of relying on the pharmaceutical industry to underwrite
the cost of drug development works extremely well in many instances, but
appears to present some limitations with regard to the development of pharma-
cotherapy for addiction in general, and specifically ibogaine.
In the public sector, the major economic incentives for the development of
addiction treatment are the saved costs associated with preventing lost economic
productivity, medical morbidity, or crime. In the private sector, decisions are
based on weighing the expense of development against the expected profit, and
not the magnitude of saved economic or social costs. Owing to limited financial
incentives in the form of insurance reimbursements and a perceived lack of
“breakthrough” compounds, the U.S. pharmaceutical industry has not generally
viewed addiction as an attractive area for development (203), and expenditures
for the development of medications for addiction are small relative to those to
develop drugs for other indications. Ibogaine is particularly unattractive to
industry for several reasons: its mechanism of action is apparently complex and
incompletely understood, it may present significant safety issues, it is a naturally
occurring alkaloid whose structure cannot itself be patented, and some of its use
patent are close to expiration.
There is arguably an important role for academic/public-sector development in
the case of a theoretically interesting drug with a limited profit potential and
significant developmental expense such as ibogaine. However, the entire annual
expenditures for medications development in NIDA, which accounts to about
90% of U.S. public sector spending on developing addiction pharmacotherapy, is
on the order of approximately $60 million, a fraction of the average cost of
31
1. ibogaine: a review
successfully developing a drug to market, which is estimated to exceed $300
million (204). Opportunities to fund research on ibogaine are limited by factors
that generally affect the development of other drugs to treat addiction: a limited
public sector budget in the presence of disproportionately low private-sector
expenditures on the development of pharmacotherapies for addiction relative to
other indications (203).
B. Political Issues
The chapter by Alper et al. in this volume describes the medical subculture of
the informal ibogaine treatment scene and the political subculture of advocacy for
the development and availability of ibogaine. These scenes are a distinctive and
significant aspect of ibogaine’s history, which arguably have impacted on
decisions regarding its development. From a clinical standpoint, the informal
treatment subculture has been an important source of information on human
experience with ibogaine (32).
From a political or historical standpoint, the informal treatment subculture has
viewed itself as a form of activism or civil disobedience on the part of its partic-
ipants seeking a treatment, despite a lack of official approval (34). Ibogaine has
been associated with a vocal activist subculture, which views its mission as
making controversial treatments available to a stigmatized minority group of
patients suffering from a life-threatening illness, and has utilized tactics intended
to engage the attention of the press (34). These confrontational media-oriented
tactics may well have provoked negative reactions at times, but may also have
influenced Curtis Wright, the former FDA ibogaine project officer, to write in
1995 that “. . . a significant portion of the public we serve believes the drug merits
investigation” (205).
X. Conclusions
Evidence that supports the possible efficacy of ibogaine as a treatment for
addiction includes case reports in humans, and effects in preclinical models of
drug dependence. The case report evidence has mainly involved the indication of
acute opioid withdrawal, and there appears to be consistency between earlier
observations derived from informal treatment contexts (32-36,146-150) and more
recent work from a setting that appears to conform to a conventional medical
model (123, Mash et al. in this volume). The continued existence of informal
treatment scenes parallels case report evidence indicating possible efficacy.
Animal work has provided observations of attenuation of opiate withdrawal signs
32 kenneth r. alper
and reductions of self-administration of a variety of drugs including morphine,
cocaine, alcohol, and nicotine. Preclinical models have also yielded evidence that
with respect to certain abused drugs, ibogaine may dampen responses that may
be associated with dependence, such as dopamine efflux in the NAc or locomotor
activation.
Ibogaine’s pharmacologic profile includes interactions with multiple
neurotransmitter systems that could plausibly be related to addiction, including
NMDA, nicotinic, mu- and kappa-opioid, and serotonergic systems. The putative
efficacy of ibogaine does not appear fully explainable on the basis of interactions
with any single neurotransmitter system, or on the basis of currently utilized
pharmacologic strategies such as substitution therapies, or monoamine reuptake
inhibition. Ibogaine’s effects may result from interactions between multiple
neurotransmitter systems, and might not be attributable to actions at any single
type of receptor. The apparently persistent effect of ibogaine has been suggested
to involve a long-lived metabolite. Some evidence suggests effects on second
messenger signal transduction, an interesting possibility that could conceivably
result from interactions between multiple neurotransmitter systems and produce
persistent effects lasting beyond the duration of occupancy at receptor sites. Work
with ibogaine congeners suggests that other iboga alkaloids can be developed that
might minimize unwanted toxic, or possibly behavioral effects, while retaining
apparent efficacy in drug dependence. In summary, the available evidence
suggests that ibogaine and the iboga alkaloids may have efficacy in addiction on
the basis of mechanisms that are not yet known and which can possibly be
dissociated from toxic effects, and may present significant promise as a paradigm
for the study and development of pharmacotherapy for addiction.
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