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Pharmacokinetic and behavioural profile of THC, CBD, and THC+CBD combination after pulmonary, oral, and subcutaneous administration in rats and confirmation of conversion in vivo of CBD to THC


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Metabolic and behavioural effects of, and interactions between Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are influenced by dose and administration route. Therefore we investigated, in Wistar rats, effects of pulmonary, oral and subcutaneous (sc.) THC, CBD and THC+CBD. Concentrations of THC, its metabolites 11-OH-THC and THC-COOH, and CBD in serum and brain were determined over 24 h, locomotor activity (open field) and sensorimotor gating (prepulse inhibition, PPI) were also evaluated. In line with recent knowledge we expected metabolic and behavioural interactions between THC and CBD. While cannabinoid serum and brain levels rapidly peaked and diminished after pulmonary administration, sc. and oral administration produced long-lasting levels of cannabinoids with oral reaching the highest brain levels. Except pulmonary administration, CBD inhibited THC metabolism resulting in higher serum/brain levels of THC. Importantly, following sc. and oral CBD alone treatments, THC was also detected in serum and brain. S.c. cannabinoids caused hypolocomotion, oral treatments containing THC almost complete immobility. In contrast, oral CBD produced mild hyperlocomotion. CBD disrupted, and THC tended to disrupt PPI, however their combination did not. In conclusion, oral administration yielded the most pronounced behavioural effects which corresponded to the highest brain levels of cannabinoids. Even though CBD potently inhibited THC metabolism after oral and sc. administration, unexpectedly it had minimal impact on THC-induced behaviour. Of central importance was the novel finding that THC can be detected in serum and brain after administration of CBD alone which, given the increasing medical use of CBD-only products, has important legal and forensic ramifications.
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Pharmacokinetic and behavioural prole
of THC, CBD, and THC+CBD combinatio
n after pulmonary, oral, and subcutaneous
administration in rats and conrmation
of conversion in vivo of CBD to THC
, Libor Uttl
, LukášKadeřábek
, Marie Balíková
Eva Lhotková
, Rachel R. Horsley
, Pavlína Nováková
Klára Šíchová
, Kristýna Štefková
, Filip Tylš
, Martin Kuchař
Institute of Forensic Medicine and Toxicology, First Faculty of Medicine, Charles University and General
University Hospital in Prague, 121 08 Prague 2, Czech Republic
Department of Analytical Chemistry, Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2,
Czech Republic
National Institute of Mental Health, Topolová 748, 250 67 Klecany, Czech Republic
Department of Physiology, Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2, Czech
Faculty of Food and Biochemical Technology, University of Chemistry and Technology Prague, Technická 5,
166 28 Prague 6, Czech Republic
3rd Faculty of Medicine, Charles University, Ruská 87, 100 00 Prague 10, Czech Republic
Received 23 February 2017; received in revised form 12 August 2017; accepted 22 October 2017
binol (THC);
Cannabidiol (CBD);
Metabolic and behavioural effects of, and interactions between Δ9-tetrahydrocannabinol (THC)
and cannabidiol (CBD) are inuenced by dose and administration route. Therefore we
investigated, in Wistar rats, effects of pulmonary, oral and subcutaneous (sc.) THC, CBD and
THC+CBD. Concentrations of THC, its metabolites 11-OH-THC and THC-COOH, and CBD in
serum and brain were determined over 24 h, locomotor activity (open eld) and sensorimotor
gating (prepulse inhibition, PPI) were also evaluated. In line with recent knowledge we
expected metabolic and behavioural interactions between THC and CBD. While cannabinoid
serum and brain levels rapidly peaked and diminished after pulmonary administration, sc. and
oral administration produced long-lasting levels of cannabinoids with oral reaching the highest
0924-977X/&2017 Elsevier B.V. and ECNP. All rights reserved.
Corresponding author at: National Institute of Mental Health, Topolová 748, 250 67 Klecany, Czech Republic.
E-mail address: (T. Páleníček).
European Neuropsychopharmacology (]]]])],]]]]]]
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
brain levels. Except pulmonary administration, CBD inhibited THC metabolism resulting in
higher serum/brain levels of THC. Importantly, following sc. and oral CBD alone treatments,
THC was also detected in serum and brain. S.c. cannabinoids caused hypolocomotion, oral
treatments containing THC almost complete immobility. In contrast, oral CBD produced mild
hyperlocomotion. CBD disrupted, and THC tended to disrupt PPI, however their combination did
not. In conclusion, oral administration yielded the most pronounced behavioural effects which
corresponded to the highest brain levels of cannabinoids. Even though CBD potently inhibited
THC metabolism after oral and sc. administration, unexpectedly it had minimal impact on THC-
induced behaviour. Of central importance was the novel nding that THC can be detected in
serum and brain after administration of CBD alone which, if conrmed in humans and given the
increasing medical use of CBD-only products, might have important legal and forensic
&2017 Elsevier B.V. and ECNP. All rights reserved.
1. Introduction
Given the on-going research and use of cannabis and
cannabis-derived products for medical purposes, it is parti-
cularly crucial to understand the nature of cannabinoid
interactions within the organism. Even though more than
100 phytocannabinoids have been identied in cannabis
plants (Bhattacharyya et al., 2010;Englund et al., 2016;
Hanus et al., 2016;Mechoulam et al., 2014), the two major
phytocannabinoids are Δ
-tetrahydrocannabinol (THC) and
cannabidiol (CBD), both of which have been shown to have
distinct therapeutic and adverse effects (Alexander, 2016;
Schubart et al., 2014;Whiting et al., 2015;Zhornitsky and
Potvin, 2012). While THC is the primary psychoactive
constituent of cannabis, CBD is primarily non-psychoactive
and has been shown to attenuate the behavioural and
metabolic effects of THC (Bhattacharyya et al., 2010;
Englund et al., 2013). In relation to this, recent research
on medical cannabis focuses on various THC: CBD ratios in
order to target particular therapeutic requirements. Owing
to the fact that there is great complexity in the nature of
THC - CBD interactions (McPartland et al., 2015;Reid and
Bornheim, 2001;Todd et al., 2016;Zuardi et al., 2012a), the
pharmacokinetics and behavioural effects of THC and CBD,
and especially their combination, across various forms of
administration, are not yet fully described. Furthermore,
the translation between pre-clinical and human data has
frequently been problematic because the routes of admin-
istration typically used by humans for cannabinoids, i.e.,
pulmonary (e.g., smoking, vaporisation); dermal (e.g.,
application of ointment or lotion) and oral (e.g., consump-
tion in food) are not often employed in animal studies.
In humans, pulmonary administration of cannabis pro-
duces the greatest bioavailability of THC, with serum
concentrations peaking within minutes, and subjective
effects apparent almost immediately (Huestis et al.,
1992), similar to intravenous (iv.) administration of THC
(Bhattacharyya et al., 2010;Englund et al., 2016). By
contrast, after oral administration of cannabinoids/cannabis
preparations, the onset of subjective effects is typically
delayed by 30 to 130 min and peak serum THC concentra-
tions are lower and delayed for about 1 6 hours after
ingestion, sometimes showing two peaks due to
enterohepatic circulation. Due to rst-pass liver metabo-
lism, higher levels of the psychoactive metabolite 11-
hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC) are also
typical (for review see Huestis, 2007). Compared to pul-
monary, iv. and oral administration of cannabinoids, very
little is known about the kinetics when administered via skin
compartment (transdermal and subcutaneous administra-
tion; Paudel et al., 2010;Stinchcomb et al., 2004).
Whilst THC binds to a number of non-cannabinoid recep-
tors in the brain, the primary mechanism of action of THC
responsible for its psychoactive effects is mediated via
partial agonism at cannabinoid CB
receptors (Campos
et al., 2012;Mechoulam et al., 2014). It is also the major
mechanism, via which THC mediates its pro-psychotic
adverse effects (Bhattacharyya et al., 2010;Englund
et al., 2013). In rodents, CB
receptor agonists, like THC,
induce what has been termed the cannabinoid tetrad
which is characterised by anti-nociception, catalepsy,
hypothermia and suppression of motor activity (El-Alfy
et al., 2010;Katsidoni et al., 2013). The psychotomi-
metic-like effects of THC and other CB
receptor agonists
in preclinical experiments focusing on sensorimotor gating
produced inconsistent ndings, with some studies showing
no effects, some a disruption of PPI and others a facilitation
(Gomes et al., 2014;Gururajan et al., 2011;Levin et al.,
2014;Long et al., 2010a;Long et al., 2010b,2013;Malone
and Taylor, 2006;Nagai et al., 2006;Peres et al., 2016).
Unlike THC, CBD lacks signicant psychotomimetic
effects; rather, it seems to counteract the psychotomimetic
and behavioural effects of THC, as well as showing anxio-
lytic and antipsychotic properties in and of itself
(Bhattacharyya et al., 2010;Englund et al., 2013;Long
et al., 2010b;Morgan et al., 2010;Pertwee, 2008;Schubart
et al., 2011;Varvel et al., 2006). In animal studies, again in
contrast to THC, CBD does not elicit the classic CB
mediated cannabinoid tetrad (in mice) and it produces
minimal disruption of behavioural tasks in humans, monkeys
and rodents (Lichtman et al., 1995;Winsauer et al., 1999).
This is likely because CBD has a low afnity for, and only
weakly antagonises CB
and CB
receptors (Pertwee, 2008;
Thomas et al., 1998;Zuardi et al., 2012a,2012b); more
specically at CB
receptors it acts as a negative allosteric
modulator (Laprairie et al., 2015). Instead, the major
T. Hložek et al.2
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
effects of CBD are via negative modulation of endocanna-
binoid tone through the inhibition of fatty acid-binding
proteins (FABPs) which transport endocannabinoids intra-
cellularly to a metabolising enzyme fatty acid amidohydro-
lase (FAAH) (Elmes et al., 2015) and via its inhibitory action
at anandamide transporters (Campos et al., 2013;Rakhshan
et al., 2000;Watanabe et al., 1996). CBD has, however,
further complex pharmacological actions involving other
neurotransmitter systems and receptors (Campos and
Guimaraes, 2009;Campos et al., 2012;Kathmann et al.,
2006;McPartland et al., 2015;Ryberg et al., 2007). At
sufciently high doses (120 mg/kg intraperitoneally in
mice), CBD may also inhibit hepatic microsomal drug
metabolism, which may lead to increased THC levels in
blood owing to delayed hydroxylation of THC to 11-OH-THC.
In consequence, at high doses, CBD can potentiate (rather
than ameliorate) the aforementioned effects of THC
(Bornheim et al., 1995).
The main aim of our study was to evaluate pharmacoki-
netic and behavioural effects of THC and CBD alone, and in
combination, in rats across three routes of administration:
sc., pulmonary and oral. Specically, we aimed to compare
24 hour pharmacokinetic proles of the two natural canna-
binoids and their co-administration at a 1: 1 ratio in rat sera
and brains and effects on locomotor behaviour in the open
eld and sensorimotor gating in the test of prepulse
inhibition of acoustic startle reaction (PPI ASR). The proles
of the psychoactive metabolite 11-OH-THC, and non-psy-
choactive metabolite 11-nor-9-carboxy-THC (THC-COOH)
were also evaluated. From the behavioural perspective we
hypothesised that THC would have inhibitory effects on
locomotion, that it would disrupt sensorimotor gating, and
that CBD would counteract these effects. We also expected
that the THC induced changes might be more pronounced
after oral administration because of the expected presence
of the potent psychoactive metabolite 11-OH-THC (Huestis,
Finally, since THC and CBD are chemically related com-
pounds, it has been reported that under certain (acidic)
conditions, CBD can be cyclised to THC in vitro: a partial
cyclisation of CBD to THC was reported when CBD was
machine smoked with tobacco, most likely due to acidic
conditions produced by the burned tobacco and by the
acidity of simulated gastric uids (Merrick et al., 2016;
Quarles et al., 1973;Watanabe et al., 2007). More recently,
the important question has been raised as to whether CBD
can also be converted to THC in vivo (Merrick et al., 2016).
Therefore our last aim was to ascertain whether treatment
with CBD (orally, or by any other route) can result in the
presence of THC in serum, and if so, whether this is
accompanied by THC-mediated behavioural effects.
2. Experimental procedures
2.1. Subjects
For all of the experiments, male Wistar rats (Velaz, Czech Republic)
weighing 200250 g were used. Animals were housed in standard
laboratory cages in the animal facility with controlled temperature
(22 721C), humidity (3070%), light/dark cycle (6 a.m. lights on /
6 p.m. lights off) and ad libitum access to water and standard diet.
Before testing, the animals were acclimatised to the animal facility
for 710 days, and all experiments were performed between 8:00 h
and 13:00 h, during the light phase under standard temperature and
humidity conditions already described. Unless otherwise stated,
experimental groups (drug route) for the behavioural experi-
ments consisted of 10 animals and each subject was tested only
once. Brains and sera of these rats were used also for kinetic
analyses, with 6 animals per experimental group (see Section 2.4).
All of the experiments adhered to the Guidelines of the European
Union (86/609/EU) and the directives of the Czech National
Committee for the Care and Use of Laboratory Animals. Ethical
approval for the studies was obtained from the Czech Ministry of
2.2. Drug preparation and administration
THC and CBD were obtained from THC-Pharm GmbH in a powder
form. For the pulmonary administrations, 20 mg of THC, CBD, or
their combination (THC: CBD at 1: 1 dose ratio) were dissolved in
98% ethanol in a volume of 200 μl and dropped on the metal-wired
liquid pad purchased with the vaporiser and dried for 1 min. New
liquid pads were used for each administration. Cannabinoids were
then delivered via an in-house set-up consisting of a Volcanos
vaporiser and a hermetically closed plastic inhalation box (volume
9.5 L). Vaporisation was held at 226 1C for 45 sec; 4 animals were
kept together in the box and inhaled the vaporised air for 5 min
(including 45 sec of vaporization). Intact animals placed for the
same period of time in the box, without vaporizing, served as
controls. For sc., and oral administration, THC, CBD and THC+CBD
were dissolved in pharmaceutical grade sunower oil (oleum
helanti) and administered at a dose of 10 mg/kg of each drug or a
mixture of 10 mg/kg THC +10 mg/kg CBD in a volume of 0.5 ml/kg,
which was then delivered by sc. injection, or directly to the
stomach by oral gavage. Control animals were administered corre-
sponding amounts of sunower oil as vehicle. For oral administra-
tion, in order to control for effects of stomach contents on
absorption, the rats were denied food for 12 h prior to drug
administration. The doses used in the current study were selected
according to animal and clinical studies in which: 1) THC shows
behavioural locomotor effects and induces psychotic-like symptoms
in animals (El-Alfy et al., 2010;Katsidoni et al., 2013;Nagai et al.,
2006;Wiley and Burston, 2014); 2) doses of CBD that were effective
in humans to treat schizophrenia, have shown some antagonising
effects on THC and have also shown some antipsychotic-like
properties in rodents (Bhattacharyya et al., 2010;Englund et al.,
2013;Gomes et al., 2014;Leweke et al., 2012;Pedrazzi et al.,
2.3. Blood and tissue collection
In order to minimise the number of animals used, the animals from
behavioural experiments were subsequently used for the kinetic
study. The rats were humanely killed at 0.5, 1, 2, 4, 8 and 24 h (in
batches of six) after oral and sc. administration. After pulmonary
administration, samples at two additional timings were also col-
lected at 0 and 15 min after removal from the inhalation box. All
experimental groups for kinetics comprised six animals per time
point for each separate drug x route treatment. Additional animals
had to be used for time points shorter than 1 hour, some of which
came from the control group. To allow an interval between
behavioural testing and kinetics data collection, these animals
remained undisturbed in a home cage for at least two more days
and subsequently they were exposed to inhalation of cannabinoids.
Separated sera and brains were collected and kept at 20 1C until
the toxicological analysis.
3Pharmacokinetic and behavioural prole of THC, CBD, and THC +CBD
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
2.4. Quantication of THC, 11-OH-THC, THC-COOH and
Cannabinoids were determined by an in-house validated and
certied GCMS method (certied by Police Presidium of the CR,
ref. no.: PPR-31123-7/CJ-2015990530 / evidence no.: 16/2015). A
total of 10 μl of deuterated CBD-d3/THC-d3/ 11-OH-THC-d3 (5 ng/
μl) internal standard solution was added to each 1.0 ml sample of
serum or brain methanol homogenate (5 ml). For brain analysis, 1 g
of brain tissue was homogenised in 5 ml of methanol. Homogenised
brain samples were frozen at 20 1C in an ethanol bath for 10 min
and then centrifuged at 4 200 rpm for 2 min. Supernatant (4 ml) was
placed in a glass tube and evaporated to 200300 μl. Serum and
brain extracts were diluted with a 4 ml sodium acetate buffer with
a pH of 4.0 (0.01 mol/l). Serum and brain cannabinoids were
extracted with SPE columns (Bond-ELUT, 130 mg, Agilent Technol-
ogies) and eluted with hexan/ethyl acetate (1:4 v/v) and dried
under a nitrogen gas stream in a 400 μl glass insert placed in a
1.5 glass vial. The samples were derivatised with 100 μlof
N-Methyl-N-(trimethylsilyl) triuoroacetamide (MSTFA) for 20 min
at 80 1C. Quantication of extracted cannabinoids was performed
by gas chromatography-mass spectrometry (GCMS) (GC7860/5742C
MSD, Agilent Technologies) using electron impact ionization in the
selective ion mode (CBD: m/z 391; CBD-d3: m/z 394; THC: m/z 386;
THC-d3: m/z 389; 11-OH-THC: m/z 371; 11-OH- THC-d3: m/z 374;
THC-COOH: m/z 371; THC-COOH:-d3: m/z 374). Calibration curve
ranges were prepared by spiking drug-free bovine serum or drug-
free rat brain homogenate for serum and brain analysis, respec-
tively, at concentrations of (i) 2100 ng/ml CBD, THC, 11-OH-THC
and THC-COOH; (ii) 1001 000 ng/ml CBD, THC, 11-OH-THC and
THC-COOH. Limits of detection (LOD) and quantication (LOQ) were
1 ng/ml and 2 ng/ml, respectively. The spiked samples were
vortexed and treated identically to the experimental samples.
2.5. Behavioural testing
Behavioural testing was performed 5 min after inhalation, 60 min
after sc. administration and 120 min after oral administration of the
cannabinoids and vehicle according to the estimated maximal peak
of cannabinoid serum levels (Huestis et al., 1992), the selection of
which was subsequently conrmed by our kinetic ndings. The
general behavioural testing procedures were identical to our
previous studies (Horsley et al., 2016;Palenicek et al., 2013;
Palenicek et al., 2016), briey:
Open eld test: a square black plastic open eld arena (68 68
30 cm) was placed in a soundproof and diffusely lit room.
Animals were placed into the centre of the arena and the length
and spatial characteristics of their trajectory were registered for
30 min and pre-processed by an automatic video tracking system for
recording behavioural activity (EthoVision Color Pro v. 3.1.1,
Noldus, Netherlands). Locomotor activity was analysed in 5 min
time intervals. The spatial characteristics of locomotor activity
were recorded in 5 5 grid of virtual zones with 16 located
peripherally and 9 centrally. Frequency (f) of line crossings into
different zones of the arena was used to calculate thigmotaxis ( =
peripheral zones
all zones
) which indicates the probability of appear-
ance in peripheral zones. Time spent in the centre of the arena
) was calculated as a summation of the time spent in all
9 central zones (
centre zones
Prepulse inhibition of acoustic startle response: PPI ASR was
tested in a startle chamber (SR-LAB, San Diego Instruments,
California, USA). Two ventilated startle chambers (SR-LAB, San
Diego Instruments, California, USA) were calibrated to ensure
equivalent stabilimeter sensitivity between the chambers. The rats
were acclimatised to the startle chamber two days before treat-
ment with a short paradigm consisting of 5 min of background noise
(75 dB white noise) and a subsequent presentation of 6 pulse alone
stimuli (125 dB/20 ms). Startle data were not recorded for accli-
matisation. On the day of the test, a total of 72 trials were held
with an inter-trial interval (ITI) of 420 s (mean ITI: 12.27 s). Rats
were acclimatised to the startle chamber for 5 min, during which
time a 75 dB background white noise was continuously presented.
Six 125 dB/40 ms duration pulse alone trials were then delivered to
establish the baseline acoustic startle response (ASR) for the
subsequent calculation of habituation. Subsequently, 60 trials were
presented in a pseudorandom order as follows: (A) pulse alone:
40 ms 125 dB; (B) prepulse-pulse: 20 ms 83 dB or 91 dB prepulse, a
variable (30, 60 or 120 ms) inter-stimulus interval (ISI: mean 70 ms),
then 40 ms 125 dB pulse; (C) 60 ms no stimulus. Finally, six pulse
alone (40 ms 125 dB) trials were delivered. Habituation was calcu-
lated by the percentage reduction in startle values from the initial
six baseline trials to the nal six trials. PPI was calculated as:
[100(mean prepulsepulse trials / mean pulse alone trials)
100]. Mean ASR was derived from the pulse alone trials. The
average startle response (the area under the curve in arbitrary
units, AVG) was used for the calculation of the dependent variable.
Animals with an ASR AVG response lower than 10 were excluded
from further analysis as non-responders.
2.6. Statistical analysis of behavioural data
Analyses of behavioural data used IBM SPSS version 22 or MS Ofce
Excel. In all cases, the criterion for rejection of the null hypothesis
for po0.05, and all tests were two tailed. Factorial and one-way
ANOVAs (Analysis of Variance) were used to analyse the data,
according to the specic experimental design in use. Where time
blocks was included in the ANOVA (locomotor trajectory data),
pairwise comparisons of the overall behavioural curves were
planned using contrast analyses according to the method described
by (Abelson and Prentice, 1997), otherwise (for PPI, total locomo-
tion, thigmotaxis and T
), independent t-tests were planned to
follow up signicant main effects or interactions. Where Mauchly's
test of sphericity (repeated measures ANOVA) or where Levene's
test for unequal variances (independent t-tests) were signicant,
adjusted statistics are reported. For Abelson's contrasts, since a
mixed design was used, the pooled error term and pooled degrees
of freedom were calculated and are reported. Recalculated and
adjusted degrees of freedom are rounded to whole numbers for
presentational purposes.
2.6.1. Open eld
An overall total locomotion was analysed by a 4 (drug) 3 (route)
independent ANOVA with drug (THC, CBD, THC +CBD or vehicle) and
route (sc., pulmonary, oral) as independent factors. Locomotor
trajectory data in 5 min time blocks were analysed using a 4 3
6 mixed factorial ANOVA with drug (THC, CBD, THC +CBD or vehicle)
and route (sc., pulmonary, oral) independent factors, and time
blocks (6 5 min) as a repeated measures factor, followed by
Abelson's contrast analyses to compare (within each route) the
characteristic patterns of locomotor effects (across time blocks) of
the different cannabinoids with vehicle, and with one another.
and thigmotaxis data were each analysed using a 4
3 factorial ANOVA with drug (THC, CBD, THC +CBD or vehicle) and
route (sc., pulmonary, oral) as independent factors.
2.6.2. Prepulse inhibition
ASR data were screened for non-responders (startle amplitude
o10); 14 oral THC and THC +CBD rats were excluded on this basis.
As a result, orally administered groups were excluded entirely from
subsequent habituation and PPI analyses, and the oral route was
dropped as a level of the route factor (leaving sc. and pulmonary
administration groups for analysis). Habituation and PPI were
therefore analysed using a 4 2 factorial ANOVA, with drug
T. Hložek et al.4
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
(THC, CBD, THC+CBD, or vehicle) and route (sc. or pulmonary) as
independent factors.
3. Results
3.1. Cannabinoid levels in blood and brain tissue
In the case of sc. administration, the concentration of THC was
approximately four times higher and CBD two times lower during
THC+CBD co-administration in both the serum and brain tissue
compared to single cannabinoid administration. Administration by
the sc. route also revealed two peaks, possibly indicative of a two-
compartment model. CBD sc. resulted in a measurable THC serum
concentration but only 4 h and 8 h after dosing (Figure 1).
After pulmonary administration of cannabinoids, their serum
levels peaked just after removal from the inhalation box while the
brain levels peaked at 15 min after dosing, and then gradually
decreased. The pharmacokinetic prole after co-administration of
THC+CBD was not different to the proles of CBD or THC alone. The
maximum brain cannabinoid concentrations were approximately
three times lower in comparison with serum concentrations
(Figure 2).
Following oral administration each of the cannabinoids or their
combination, both serum and brain levels peaked at 2 h post
administration and with THC alone the brain concentrations
remained high for another 2 h. Serum and brain concentrations of
CBD were approximately two to threefold lower during THC+CBD
co-administration than in the case of administration of CBD alone.
On the contrary, concentrations of THC were approximately two
times higher during THC+CBD co-administration in comparison with
THC alone. Importantly, oral administration of CBD again resulted in
measurable THC serum concentrations along with CBD concentra-
tions, but here were no detectable levels in the brain (Figure 3). To
nd out whether this was related to the fact that the levels in the
brain were below the limit of detection (LOD) of the method, we
administered an additional two animals with 60 mg/kg of oral CBD,
and the sera and brains were analysed 2 h after administration. The
concentrations of cannabinoids detected were as follows: (A) for rat
1 serum CBD was 990.9 ng/ml and THC 19.1 ng/ml, brain levels
were 1075.9 ng/g for CBD and 33.3 ng/g for THC, (B) for rat 2 serum
CBD was 723.1 ng/ml and THC below the limit of detection, brain
levels were 871.9 ng/g for CBD and 6.8 ng/g for THC. The oral
administration also resulted in a signicant accumulation of canna-
binoids in brain tissue, which in the case of THC was more than
double the levels in the serum.
The pharmacokinetic prole of 11-OH-THC after each route of
administration reached the highest concentrations after oral admin-
istration; it accumulated in the brain at concentrations of approxi-
mately 200 ng/g, which is comparable to THC brain levels after
vaporisation (Figs. 13). It was not detected at measurable levels
after administration of CBD alone.
The non-psychoactive metabolite THC-COOH had a delayed peak
between 48 h after administration, remained detectable 24 h later
and had very low levels compared to 11-OH-THC; after pulmonary and
sc. administration it was not detected in the brain tissue (Tab l e 1).
3.2. Behavioural tests
3.2.1. Open eld
Total locomotion summed across the time blocks (Figure 4) showed
a signicant main effect of drug, route and a signicant interaction,
minimum F (2, 18) =13.49, p=0.001. Independent t-tests (within
route) showed after sc. treatment, there was no signicant
difference between vehicle and each of the cannabinoids, but after
pulmonary treatment, there were signicant reduction of locomo-
tion after each of the cannabinoids compared to vehicle, minimum t
(18) =2.96, p=0.01. Similarly after oral treatment THC and THC
+CBD signicantly reduced total locomotion, but on the contrary
Figure 1 Pharmacokinetic proles of CBD, THC and CBD+THC in serum and brain tissue after subcutaneous administration 10 mg/
kg (six rats per time point). n.d. =not detected.
5Pharmacokinetic and behavioural prole of THC, CBD, and THC +CBD
Figure 2 Pharmacokinetic proles of CBD, THC and CBD+THC in serum and brain tissue after pulmonary administration of 20 mg
vaporised per 4 rats, inhalation for 5 min (six rats per time point).
Figure 3 Pharmacokinetic proles of CBD, THC and CBD+THC in serum and brain tissue after oral administration 10 mg/kg (six rats
per time point). n.d. =not detected.
T. Hložek et al.6
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
CBD increased it, minimum t(18) =3.92, p=0.001. Comparisons
of routes of administration within each drug treatment showed that
THC and THC+CBD orally had signicantly lower locomotion
compared to sc. and pulmonary administration of these compounds,
by contrast CBD increased locomotion, minimum t(18) =4.36, p=
The analysis of locomotor data in 5 min time blocks (Figure 5)
showed signicant main effects for blocks (shown as a typical
progressive decline in locomotor activity over 30 min), for drug and
for route, minimum F (2, 108) =13.49, p=0.001. All possible two-
way interactions were signicant (drug blocks, route blocks,
drug route), minimum F (10, 371) =2.66, p=0.003. The drug
route blocks interaction was also signicant: F (21, 371) =
3.46, p=0.001. Figure 6 shows characteristics trajectories.
Subsequent contrast analysis between cannabinoids and vehicle
for the sc. route showed marginally signicant differences between
the behavioural curves of vehicle versus THC and CBD, F (1, 256) =
3.01, p=0.08, and F (1, 256) =3.23, p=0.07, respectively; the
THC+CBD combination did not differ from vehicle and no differ-
ences between the cannabinoids when delivered via the sc. route
were observed.
Within the pulmonary route, THC was different to vehicle,
contrast F (1, 256) =6.00, p=0.015, but CBD and THC +CBD did
not differ from vehicle. There were no signicant differences
between CBD versus THC, or CBD versus THC+CBD, although the
difference between THC versus THC+CBD was marginally signicant
(contrast F (1, 256) =3.03, p=0.08). This was manifested as
slightly higher activity for THC in early blocks, and some minor
uctuations in responding from the THC+CBD group, whilst requir-
ing comment, does not merit further discussion.
When administered orally, THC showed signicantly reduced
locomotor responding, which persisted over time compared to
vehicle, contrast F (1, 256) =24.63, p=0.001, and a similar
pattern was shown after THC+CBD, F (1, 256) =22.87, p=0.001.
Even though the total distance travelled was longer in CBD than in
vehicle, the contrasts for behavioural curves were not signicantly
different. Locomotor activity was also signicantly reduced under
THC and the THC+CBD combination compared to CBD alone,
minimum contrast F (1, 256) =15.51, p=0.001, and THC and
THC+CBD did not differ signicantly from one another.
Within drug contrasts of the curves over time showed that for
CBD, there were signicant differences between routes, where oral
administration induced higher locomotor activity than sc. or
pulmonary administration, minimum contrast F (1, 256) =4.10, p
=0.05. Oral THC and THC+CBD signicantly reduced locomotion
compared to sc. and pulmonary administration, minimum contrast F
(1, 256) =10.23, p=0.001, and there were no signicant
differences between the pulmonary and sc. routes.
For T
(Figure 7), there were no signicant main effects of
drug or route, maximum F (2, 108) =1.02, p=0.37, but there was
Table 1 Pharmacokinetic proles of THC-COOH in serum and brain tissue after subcutaneous, pulmonary and oral
administration of THC (20 mg vaporised per 4 rats, inhalation for 5 min and 10 mg/kg for oral and subcutaneous
administration, six rats per time point). n.d. =not detected.
Time of Sampling
Route 0 min 15 min 0.5 h 1 h 2 h 4 h 8 h 24 h
Subcutaneous serum (ng/ml) –– 1.0 6.3 4.4 11.9 5.4 2.4
brain (ng/g) –– n.d. n.d. n.d. n.d. n.d. n.d.
Pulmonary serum (ng/ml) 1.4 2.0 1.9 2.6 1.6 2.6 3.2 0.9
brain (ng/g) n.d. n.d. n.d. n.d. n.d. n.d. n.d. n.d.
Oral serum (ng/ml) –– 4.1 8.9 15.0 34.7 43.3 17.7
brain (ng/g) –– n.d. 1.5 5.3 15.7 12.8 4.6
Figure 4 Mean trajectory length over 30 min. after subcutaneous, pulmonary and oral administration of vehicle (VEH), THC, CBD,
or THC+CBD. Error bars show 71 S.E.M. Asterisks indicate signicant differences from corresponding vehicle, po0.05.
7Pharmacokinetic and behavioural prole of THC, CBD, and THC +CBD
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
a signicant drug x route interaction, F (6, 108) =3.46, p=0.004.
Whilst within the sc. route, none of the cannabinoids showed
signicant differences from vehicle, within the pulmonary route,
each of the cannabinoids signicantly reduced T
, most mark-
edly for THC+CBD, minimum t(18) =2.24, p=0.038. Within the
oral route, THC signicantly reduced time in the centre compared
to vehicle, t(18) =2.86, p=0.010, but CBD alone, or in
combination with THC did not, maximum t(18) =1.49, p=1.52.
There were no differences between THC or CBD and THC +CBD
when delivered sc. or orally, however, with pulmonary administra-
tion, THC+CBD signicantly reduced time in the centre compared
to CBD alone, t(18) =3.62, p=0.005, and similarly, THC +CBD
signicantly reduced time in the centre compared to THC alone, t
(18) =3.73, po0.002. Finally, there were no signicant differences
between THC and CBD, irrespective of route of administration.
There were signicant main effects of drug and route on
thigmotaxis, minimum F (2, 108) =3.57, p=0.032, as well as a
signicant drug route interaction, F (6, 108) =6.28, p=0.001
(Figure 7). Within the sc. route, CBD affected thigmotaxis, reducing
the likelihood of appearance in the periphery compared to vehicle,
t(18) =2.10, p=0.05, but THC and THC+CBD did not. After
pulmonary treatment, THC and CBD alone reduced thigmotaxis
compared to vehicle, minimum t(18) =3.02, p=0.007, but THC
+CBD did not signicantly affect this measure. Within the oral
route, THC and CBD alone did not signicantly affect thigmotaxis,
however THC+CBD signicantly reduced it, compared to vehicle, t
(18) =2.89, p=0.010. When comparing cannabinoids with one
another, there were no differences on thigmotaxis between THC or
CBD versus THC+CBD, when treated sc. and via pulmonary admin-
istration. However after pulmonary administration, THC+CBD
increased thigmotaxis compared to CBD alone and to THC alone,
minimum t(18) =3.42, p=0.003. After oral treatment, THC+CBD
decreased thigmotaxis compared to CBD and THC, t(18) =2.51, p
=0.02, and there were no signicant differences between THC and
3.2.2. Prepulse inhibition
ASR data were screened prior to analysis for non-responders (ASR o
10) and a number of rats were excluded on this basis, most notably
from the groups that were orally administered THC (before exclu-
sions mean ASR =20.58, SEM =6.69; 5 rats needed excluding) and
THC+CBD (before exclusions mean ASR =9.38 SEM =3.13; 9 rats
required excluding). Given the oor in responding (where any
further decrease in startle would not be detectable: (Palenicek
et al., 2013)) and the number of exclusions, the oral route was
dropped from subsequent factorial analysis of habituation and PPI
data. After excluding the oral group, ASR analysis showed no
signicant main effects or interactions, maximum F (3, 64) =
0.71, p=0.55 (Table 2). Likewise, habituation data showed no
signicant main effects or interactions, maximum F (3, 63) =0.32,
p=0.81. Therefore neither ASR nor habituation showed baseline
differences that might confound interpretation of PPI data.
On PPI there was a signicant main effect of drug, F (3, 64) =
4.13, p=0.01 (Figure 8), but no signicant main effect of route, or
drug route interaction. Independent t-tests by drug on the main
effect (irrespective of route) showed that neither THC nor THC
+CBD were different from vehicle (THC was marginally, maximum t
(32) =1.79, p=0.08), but there was a signicant difference
between CBD and vehicle, t(33) =2.30, po0.05. THC and CBD did
not differ from one another, however, each was signicantly
different to THC+CBD, minimum t(34) =2.64, po0.01.
Table 2 shows the descriptive statistics for the non-signicant
interaction, and also includes values (after exclusions) for the
orally administered groups. Independent t-tests were used to
compare useable oral PPI data; these showed that oral CBD did
not differ to oral vehicle, however there were differences between
the oral and the sc. and pulmonary routs, minimum t(18) =2.09, p
4. Discussion
The main ndings of the pharmacokinetic experiments were:
1) cannabinoids were best absorbed after oral administra-
tion, after which brain levels were several times higher
compared to sc. and pulmonary administration; 2) pulmonary
administration yielded an almost immediate peak in canna-
binoid levels followed by their rapid elimination; in contrast,
peaks appeared later after sc. and oral administration, and
cannabinoids were still detectable 24 hours later; 3) sc. as
well as oral, but not pulmonary, co-administration of THC
with CBD yielded an increase in serum and brain levels of
THC compared to THC alone; 4) the psychoactive metabolite
11-OH-THC accumulated in the brain tissue compared to sera
Figure 5 Mean trajectory length per 5 min time block over 30
min after subcutaneous (A), pulmonary (B) and oral
(C) administration of vehicle (VEH), THC, CBD, THC +CBD. Error
bars show 7SEM. Asterisks indicate signicant differences from
corresponding vehicle, po0.05.
T. Hložek et al.8
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
and its abundance was highest after oral administration; and
5) the non-psychoactive metabolite THC-COOH was detected
with a delayed peak but surprisingly only in very low
concentrations. A novel and partly unexpected nding was
the presence of THC in sera after oral and after sc.
administration when only CBD alone had been administered.
An additional experiment with high dose of oral CBD (60 mg/
kg) conrmed the presence of THC also in the brain. The
main behavioural effects of cannabinoids were: 1) moderate
locomotor inhibition after pulmonary administration of can-
nabinoids, 2) strong sedation / catalepsy after oral admin-
istration of THC and THC +CBD; 3) mildly elevated
locomotor activity after oral CBD; and 3) CBD disrupted PPI
(main effect irrespective of pulmonary or sc. administration
route) compared to vehicle.
4.1. Pharmacokinetics
Pulmonary administration is the most typical method of
cannabis consumption in humans as either a recreational
drug or experimental medicine. In accordance with our
current ndings, peak plasma THC concentrations in humans
are usually reached within few minutes after smoking
(Huestis, 2007;Manwell et al., 2014). While serum levels
rapidly decreased, the brain levels, although having a
maximum three times lower than sera, remained high for
one hour after administration. This is consistent with the
nding that peak behavioural/cognitive effects in humans
appear with a delay compared to peak serum levels
(Huestis, 2007;Manwell et al., 2014). CBD bioavailability
was about two thirds of THC. One possible explanation may
be the different thermodynamics of the two compounds
with CBD having a slightly higher boiling point than THC
(160180 1Cversus 157 1C, respectively; (McPartland and
Russo, 2001)), which might, in turn, lead to a lower total
amount of vaporised CBD. Pulmonary THC +CBD did not
produce different pharmacokinetic proles for the two
compounds compared to when CBD or THC were adminis-
tered alone. Finally, no THC levels were detected after
pulmonary CBD administration, which is in line with (Quarles
et al., 1973) who reported that CBD did not form Δ
when marijuana cigarettes were smoked either by a human
subject or by a smoking machine without concomitant use of
As expected and contrary to pulmonary administration of
cannabinoids, the oral administration of both compounds
had much slower kinetics with a peak two hours after
Figure 6 Characteristic trajectories after subcutaneous, pulmonary and oral administration of vehicle (VEH), THC, CBD, THC +CBD.
Figure 7 Mean T
(A) and thigmotaxis (B) over 30 min
after subcutaneous, pulmonary and oral administration of
vehicle (VEH), THC, CBD, or THC +CBD. Error bars show 7
SEM. Asterisks show signicant differences from corresponding
9Pharmacokinetic and behavioural prole of THC, CBD, and THC +CBD
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
administration. Interestingly, even though peak serum levels
were comparable to pulmonary administration, brain levels
were three to six times higher and remained very high for
four hours, which clearly indicates that compounds are
gradually accumulated into lipophilic brain tissue. This, in
turn, would correspond to the prolonged effects of orally
administered cannabis products. A very interesting nding is
that despite the reported very low bioavailability of canna-
binoids after oral administration (620% for THC and 619%
for CBD (Huestis, 2007;Klumpers et al., 2012;Zhornitsky
and Potvin, 2012)), in our case, we saw the best bioavail-
ability compared to both alternative methods of adminis-
tration. The fact that cannabinoids were dissolved in oil and
that our animals fasted before administration may have led
to better bioavailability compared to a situation when pure
compounds, e.g., a solution encapsulated or dissolved in
water, are administered. The very high brain levels were
also reected in the behavioural tests, as discussed below.
There are two very important issues of the oral admin-
istration. Firstly, co-administration of THC+CBD changed
the pharmacokinetic proles of both cannabinoids com-
pared to administration of each cannabinoid separately.
Specically, the maximum mean peak serum concentration
of CBD was three times lower during THC +CBD co-admin-
istration than after CBD alone, while the maximum mean
peak concentration of THC was two times higher compared
to THC alone. Similar pharmacokinetic proles were estab-
lished in brain tissue, whereby the maximum peak concen-
tration of cannabinoids was approximately two times higher.
The effect on THC is most likely related to CBD-induced
inhibition of its liver metabolism, since CBD acts as a potent
inhibitor of cytochrome P450 enzymes CYP1A2, CYP2B6,
CYP2C9, CYP2D6 and CYP3A4 (Zhornitsky and Potvin, 2012).
Even though the abundance of the main psychoactive
metabolite 11-OH-THC was several times higher compared
to pulmonary administration, almost no difference in its
concentration was observed between THC alone and the
THC+CBD groups indicating that this particular metabolic
pathway was not affected. The presence of high levels of
this potent metabolite most likely accounted for/added to
the robust behavioural effects observed after oral adminis-
tration. In contrast to THC, the lower CBD levels compared
to CBD alone treatment are difcult to explain. Since CBD is
metabolised by various enzymes at cytochrome P450
(Jiang et al., 2011), one of the possible explanations could
be an induction of CBD metabolism by THC. However we did
not nd any literature to directly support this. Interestingly,
a very similar nding has been shown in humans; when same
doses of THC and CBD were co-administered via different
routes of administration, CBD had lower plasma levels
compared to THC (Guy and Robson, 2004;Huestis, 2007).
So we might assume that several metabolic interactions can
occur between THC and CBD and many of these remain to be
identied. The second important nding is that administra-
tion of CBD alone resulted in measurable concentrations of
THC in serum, ranging from 2.0 to 68.6 ng/ml. Surprisingly,
with this current dose we did not detect THC in the brain
Table 2 ASR, habituation and PPI: Means (S.E.M.s are shown in italics) for the cannabinoid (THC, CBD, THC+CBD) by route
(subcutaneous, pulmonary, oral). Values reect AVG amplitude, after exclusions where ASRo10 arbitrary units. The values
presented under THC and THC+CBD oral administration (bold and underlined) correspond to reduced number of animals after
exclusion of ASR non-responders; remaining subjects were: n=5 for THC group and n=1 for THC +CBD group.
Drug Treatment
Measure Route Vehicle THC CBD THC+CBD
ASR (arbitrary units) Subcutaneous 162.57 (36.22) 189.73 (43.51) 132.37 (16.76) 231.33 (57.35)
Pulmonary 112.28 (25.79) 213.06 (47.70) 155.83 (31.25) 146.95 (21.85)
Oral 185.00 (39.75) 35.45 (9.47) 126.33 (22.23) 27.46 (3.63)
Percentage Habituation Subcutaneous 59.93 (7.28) 58.67 (10.13) 60.53 (6.28) 52.65 (1.99)
Pulmonary 60.68 (6.17) 55.96 (.39) 57.68 (6.50) 64.01 (7.48)
Oral 51.71 (10.79) 71.11 (12.01) 44.31 (11.13) 29.07 (32.64)
Percentage PPI Subcutaneous 51.91 (6.61) 39.13 (7.09) 30.23 (8.70) 51.31 (4.74)
Pulmonary 47.36 (6.25) 37.33 (4.54) 35.06 (7.60) 55.05 (5.42)
Oral 30.03 (5.39) 39.37 (18.07) 34.81 (8.12) 19.28 (17.57)
Figure 8 Mean percentage prepulse inhibition (AVG ampli-
tude) for the signicant main effect of drug treatment (vehicle
(VEH), THC, CBD, or THC+CBD) collapsed across subcutaneous
and pulmonary routes Error bars show 71 SEM Asterisk shows
signicant difference from vehicle, connecting lines indicate
signicant inter-cannabinoid differences, po0.05.
T. Hložek et al.10
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
tissue. This led us to add an additional study with two rats
administered with a high oral dose of CBD (60 mg/kg) after
which the THC was also detected in the brain two hours
after treatment. Therefore it is possible that minimal levels
of THC could have been present in the brain following
treatment with CBD 10 mg/kg, but did not reach the limit of
detection (LOD) of our analytical method. As noted in the
introduction, previous experimental work indicated that
when CBD is degraded in an acidic environment (articial
gastric juice), it rapidly cyclises to Δ
-THC (Watanabe
et al., 2007). Recently, (Merrick et al., 2016) conrmed
the formation of psychoactive cannabinoids when CBD is
exposed to simulated gastric uid and also clearly demon-
strated acid catalysed cyclization to Δ
-THC. According to
the rst study, not only THC but also other related
hexahydrocannabinols have been associated with catalepsy,
hypothermia and antinociception in mice (Watanabe et al.,
After an initial short-lasting and low amplitude peak, sc.
administration of either THC or CBD resulted in relatively
steady serum and brain concentrations. The concentrations
of THC and CBD reached over the experimental interval
were generally an order of magnitude lower than the
respective pulmonary and oral administration of either of
the cannabinoids. Nevertheless, after sc. administration of
THC+CBD, the THC maximum mean peak concentration was
ve times higher and CBD concentration about half the
value than administration of THC or CBD alone in both the
serum and brain tissue. This presumably also indicates a
signicant inhibition of THC metabolism by CBD, as has been
already discussed for oral administration. Important nding
is that 11-OH-THC reached almost the same brain levels as
of THC when THC was administered alone. At the same time
these levels were approximately a half of THC levels when
THC+CBD were co-administered indicating that there is an
accumulation of this potent active metabolite in the brain.
Even though we did not observe much behavioural changes,
this may contribute to theoretical psychotomimetic effects
of the combination. Another observation was a second peak
of cannabinoids with a maximum after 8 h for THC and 11-
OH-THC and 4 h for CBD, which was more prominent in the
brain tissue. A theoretical explanation may be the two-
compartment pharmacokinetics model, where the cannabi-
noids are initially released to the blood stream via certain
carrier mechanisms directly after administration, while at
the same time being depot bound in the skin and fat tissue
from which they are subsequently released. Finally, sc.
administration also yielded measurable levels of THC,
indicating that cyclization may also occur in subcutaneous
fat. Again, no measurable brain THC concentrations were
The presence of THC in sera after oral as well as sc.
administration of CBD may have important psychosocial and
forensic consequences. (Merrick et al., 2016) stated that
people who are treated with high CBD doses may theoreti-
cally experience some signs of THC intoxication, e.g.,
sedation, citing child CBD studies on epilepsy. However his
paper induced vigorous opposition from other researchers
against this suggestion (Grotenhermen et al., 2017;Russo,
2017). Whilst we agree that sedation is probably not linked
to THC effects since other cannabinoids and terpenoids are
more likely responsible, however our ndings conrmed the
conversion in vivo of CBD to THC (albeit in rats at doses
several times higher compared to those typically used by
humans). CBD has become widely used in various forms,
including as a popular food supplement and a constituent of
various dermatological preparations, therefore positive test
results for THC cannot be excluded in subjects using these
CBD-based products, with obvious legal ramications (e.g.,
the capacity to drive a motor vehicle). Although the levels
of THC seem to be quite low especially in brain tissue, it is
very speculative if they might produce any objective signs
of intoxication in adults even after very high doses of CBD.
Moreover, conversion of CBD to THC in the stomach will very
much depend on the formulation in which the drug is
administered (Perez-Reyes et al., 1973) and we cannot
exclude that the administration of CBD on an empty
stomach might partially contribute to accelerated transfor-
mation of CBD to THC. A support for this can be extra-
polated from human data where the pH of stomach has been
reported to be the lowest in the morning after whole night
fasting (Brooks, 1985). Nevertheless from a forensic per-
spective, in some places around the globe there may be
zero tolerance to THC when driving and/or operating
machines or performing activities requiring increased atten-
tion, thus CBD users may inadvertently break the law, even
though the use of CBD may be legal.
Finally, very low concentrations of THC-COOH were
detected in our samples (THC: THC-COOH ratio approxi-
mately 10: 1). This is surprising, since in humans this
metabolite is the primary non-psychoactive metabolite
formed from THC, typically displaying plasma levels several
times higher than THC, especially in chronic cannabis users
(Balíková et al., 2014;Karschner et al., 2011). We found
only one study investigating at THC-COOH levels in rats
(Sprague-Dawley strain), which was in agreement with our
data and showed similar results. While THC-COOH was
detected in high concentrations in the liver microsomes of
an in vitro study, the in vivo experiments revealed 11-OH-
THC as the major metabolite in the liver homogenates,
while THC-COOH was much lower and only observed in
female rats (Narimatsu et al., 1991). Similarly, the THC:
THC-COOH ratio in Rhesus monkeys was also approximately
20: 1, thereby showing a similar trend as in rats (Ginsburg
et al., 2014). A most recent nding has shown that in male
and female Sprague Dawley rats, after intraperitoneal
administration of THC and CBD, another important meta-
bolite of THC, cannabinol (CBN) is produced; it especially
occurs after co-administration of THC with CBD. Further-
more, 11-0H-THC and THC-COOH are much more likely to be
detected in female compared to male rats (Britch et al.,
2017). Therefore, signicant interspecies and sex differ-
ences in the metabolism of THC may underlie this discre-
pancy between rats and other species.
4.2. Behavioural effects
The mild inhibitory effects on locomotion after pulmonary
administration are in line with the reported cannabinoid
tetrad (El-Alfy et al., 2010;Katsidoni et al., 2013). However
the oral administration of THC either alone, or co-adminis-
tered with CBD produced robust locomotor inhibition in the
open eld which reected profound sedation/catalepsy
11Pharmacokinetic and behavioural prole of THC, CBD, and THC +CBD
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pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
(this was also seen in the PPI ASR study, where rats treated
with oral THC or THC+CBD barely startled to unexpected
auditory stimuli). Of interest is that only oral, but not
pulmonary or sc. administration, yielded such robust effects
which indicates that different metabolites might be respon-
sible. In support of this, Marshell et al. (2014) found a lack
of cataleptogenic effect and less pronounced inhibition of
locomotion after pulmonary administration of THC and
synthetic cannabinoids versus intraperitoneal administra-
tion (Marshell et al., 2014). CBD failed to ameliorate the
observed sedation, even though after oral CBD alone
increased locomotion compared to the control group. There
was an effect of oral THC+CBD on the spatial character-
istics of the trajectory; however, we assume that this is
most likely confounded by the robust locomotor inhibition
rather than related to attenuation of exploration or anxiety.
None of the other treatments showed any signicant effects
either on locomotion or on its spatial characteristics. The
locomotor inhibitory effect ts within the know cannabinoid
tetrad and is presumably related to the high THC brain
concentrations seen with the oral dose, as a dose depen-
dency for THC induced sedation has already been described
(Shi et al., 2005;Wiley and Martin, 2003). On the other
hand, in some studies THC has been shown to have a dose
dependent bidirectional effects i.e., hyperlocomotion in
low doses and hypolocomotion or sedation at high doses (El-
Alfy et al., 2010;Katsidoni et al., 2013). However, none of
the THC treatments produced any sign of increased locomo-
tion even though the brain concentrations varied widely
across different routes of administration. Even though
highly speculative, an exception could be the increase in
locomotion after oral CBD. Low THC levels in the serum
were present in this case and even though they were not
detected in the brain because of the supposed higher LOD of
the analytical method used, these low THC levels could
theoretically be an underlying cause of the mild stimulatory
effects (El-Alfy et al., 2010;Katsidoni et al., 2013). Even
though the increase in locomotion after CBD was surprising,
it has also been recently described in Sprague Dawley rats
(Britch et al., 2017). It is highly unlikely that increased
locomotion under CBD was a result of anxiolysis, since we
saw no evidence for this in our analysis of the spatial
characteristics of locomotor behaviour.
After exclusion of the oral THC treated groups, we did not
observe any signicant baseline effects on ASR or habitua-
tion that might confound interpretation of effects of drug
and route on PPI ASR. THC marginally disrupted PPI (two-
tailed); it is of note that if one-tailed test would have been
used (to test specic hypothesis that THC disrupts PPI), it
would result in statistical signicance (p=0.04). Thus mild
pro-psychotic effects of THC may have been detected. The
disruptive effect of CBD alone was a surprise; usually the
neurobiological basis of cannabinoid induced decits in PPI,
if present, seems to be attributed to CB1 as well as
dopamine mediated mechanisms (Malone and Taylor, 2006;
Nagai et al., 2006;Tournier and Ginovart, 2014), however in
the case of CBD, with its wide pharmacological action, it
cannot be explained so easily. As stated earlier, literature
ndings on PPI are inconsistent regarding the effects of CB1
agonists (Gomes et al., 2014;Gururajan et al., 2011;Levin
et al., 2014;Long et al., 2010a;Long et al., 2010b,2013;
Malone and Taylor, 2006;Nagai et al., 2006;Peres et al.,
2016). Most likely differences according species and strain,
synthetic versus natural cannabinoids and their potency,
partial versus full agonism underlie such inconsistencies
(Levin et al., 2014;Malone and Taylor, 2006;Peres et al.,
2016). This also seems to be the truth for CBD alone e.g.,
(Gururajan et al., 2011;Long et al., 2010b). Interestingly,
even though CBD alone induced disruption in the PPI, when
co-administered with THC, there was no difference from
vehicle controls, and signicant PPI improvement compared
to both THC as well as CBD. This seems to be in accordance
with CBD's capacity to reverse PPI decits in various rodent
models of psychosis (Gomes et al., 2014;Gururajan et al.,
2011;Levin et al., 2014;Nagai et al., 2006;Pedrazzi et al.,
2015;Peres et al., 2016) and might lead to the conclusion
that a modest antipsychotic-like effect of CBD on THC
induced decit was observed.
In conclusion, in contrast to our predictions, CBD had only
an isolated antagonising effect on THC induced sensorimo-
tor decits, while it left other THC behavioural effects
unaffected and alone it produced sensorimotor gating
disruption. The present study revealed remarkable differ-
ences between cannabinoid pharmacokinetics in relation to
their route of administration and it also reveals important
pharmacokinetic/metabolic interactions of co-administra-
tion of the two main constituents of cannabis, however
these interactions were manifested only marginally in the
behavioural tasks. Contrary to other studies, we observed
good bioavailability of cannabinoids after oral administra-
tion in an oil solution, which will have applications in the
development of formulas with high therapeutic efcacy.
However, the detection of THC in the blood stream after
oral and sc. administration of CBD alone, if conrmed in
humans, may affect the development of therapeutic and
medical CBD products as well as having potential legal and
forensic implications.
Role of Funding source
Funding for this study was provided by projects MICR
VG20122015080, VI20172020056, MHCZDRO (NIMH-CZ,
00023752), European Regional Development Fund
(ED2.1.00/03.0078), and LO1611 from the MEYS under the
NPU I program, 260388/SVV/2017 and PROGRES Q35. These
institutions had no further role in the study design; in the
collection, analysis and interpretation of data; in the
writing of the report; or in the decision to submit the paper
for publication.
TomášHložek and Marie Balíková performed the analytical labora-
tory analyses and their subsequent evaluation as well as writing the
TomášPáleníček designed the whole study and experimental
protocol and participated in the behavioural and pharmacokinetic
experiments and writing the manuscript.
Authors Libor Uttl, LukášKadeřábek, Eva Lhotková, Filip Tylš,
Pavlína Nováková, Klára Šíchová, Kristýna Štefková and Martin
T. Hložek et al.12
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
Kuchařperformed the behavioural experiments, pharmacokinetic
experiments and all contributed to writing and approving the
present manuscript, Rachel Horsley contributed mainly with the
statistical analysis of the data and writing of the manuscript.
Conict of Interest
All of the authors declare that they have no conicts of
The authors would like to thank Craig Hampson, BSc. (Hons) for
helpful comments and language correction.
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15Pharmacokinetic and behavioural prole of THC, CBD, and THC +CBD
Please cite this article as: Hložek, T., et al., Pharmacokinetic and behavioural prole of THC, CBD, and THC+CBD combination after
pulmonary, oral, and subcutaneous.... European Neuropsychopharmacology (2017),
... Co-administration of CBD and another cannabinoid, tetrahydrocannabinol (THC), has already produced a better therapeutic profile than each phytocannabinoid alone [31][32][33]. This synergism between the inflammation related to the two cannabinoids has been reported in vivo. ...
... In BV2 cells, LPS also upregulated the expression of pro-inflammatory miRNAs related to Toll-like receptor (TLR) and NF-κB signaling. In contrast, CBD inhibits LPS-stimulated expression of these mRNAs [31]. ...
Full-text available
Cannabidiol (CBD), the major non-psychoactive phytocannabinoid found in cannabis, has anti-neuroinflammatory properties. Despite the increasing use of CBD, little is known about its effect in combination with other substances. Combination therapy has been gaining attention recently, aiming to produce more efficient effects. Angiotensin II activates the angiotensin 1 receptor and regulates neuroinflammation and cognition. Angiotensin receptor 1 blockers (ARBs) were shown to be neuroprotective and prevent cognitive decline. The present study aimed to elucidate the combined role of CBD and ARBs in the modulation of lipopolysaccharide (LPS)-induced glial inflammation. While LPS significantly enhanced nitric oxide synthesis vs. the control, telmisartan and CBD, when administered alone, attenuated this effect by 60% and 36%, respectively. Exposure of LPS-stimulated cells to both compounds resulted in the 95% inhibition of glial nitric oxide release (additive effect). A synergistic inhibitory effect on nitric oxide release was observed when cells were co-treated with losartan (5 μM) and CBD (5 μM) (by 80%) compared to exposure to each compound alone (by 22% and 26%, respectively). Telmisartan and CBD given alone increased TNFα levels by 60% and 40%, respectively. CBD and telmisartan, when given together, attenuated the LPS-induced increase in TNFα levels without statistical significance. LPS-induced IL-17 release was attenuated by CBD with or without telmisartan (by 75%) or telmisartan alone (by 60%). LPS-induced Interferon-γ release was attenuated by 80% when telmisartan was administered in the absence or presence of CBD. Anti-inflammatory effects were recorded when CBD was combined with the known anti-inflammatory agent dimethyl fumarate (DMF)/monomethyl fumarate (MMF). A synergistic inhibitory effect of CBD and MMF on glial release of nitric oxide (by 77%) was observed compared to cells exposed to MMF (by 35%) or CBD (by 12%) alone. Overall, this study highlights the potential of new combinations of CBD (5 μM) with losartan (5 μM) or MMF (1 μM) to synergistically attenuate glial NO synthesis. Additive effects on NO production were observed when telmisartan (5 μM) and CBD (5 μM) were administered together to glial cells.
... Evaluation of additional routes, such as the subcutaneous administration route where CBD was injected into the fatty tissue layer beneath the skin, has been shown to provide a slow and sustained release of CBD into the systemic circulation and bypass the liver first-pass metabolism [42,43]. Similar advantages were also provided by the intramuscular administration route, which involves injecting CBD directly into the muscle tissue [44]. ...
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Cannabidiol (CBD), derived from the cannabis plant, has gained significant attention due to its potential therapeutic benefits. However, one of the challenges associated with CBD administration is its low bioavailability, which refers to the fraction of an administered dose that reaches systemic circulation. This limitation necessitates the exploration of various approaches to enhance the bioavailability of CBD, thus helping to maximize its therapeutic potential. A variety of approaches are now emerging, including nanoemulsion-based systems, lipid-based formulations, prodrugs, nanocarriers, and alternative routes of administration, which hold promise for improving the bioavailability of CBD and pave the way for novel formulations that maximize the therapeutic potential of CBD in various medical conditions. This opinion piece presents the current understanding surrounding CBD bioavailability and considers strategies aimed at improving both its absorption and its bioavailability.
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Background Glioblastoma multiforme (GBM) is an aggressive cancer with poor prognosis, partly due to resistance to the standard chemotherapy treatment, temozolomide (TMZ). Phytocannabinoid cannabidiol (CBD) has exhibited anti-cancer effects against GBM, however, the ability of CBD to overcome common resistance mechanisms to TMZ have not yet been investigated. 4’-Fluoro-cannabidiol (4’-F-CBD, or HUF-101/PECS-101) is a derivative of CBD, that exhibits increased activity compared to CBD during in vivo behavioural studies. Methods This work investigated the anti-cancer activity of cannabinoids against GBM cells sensitive to and representing major resistance mechanisms to TMZ. The cannabinoids were also studied in combination with imidazotetrazine agents, and the OrbiSIMS technique was used to investigate the mechanism of action of CBD. Results CBD and 4’-F-CBD were found to overcome two major resistance mechanisms (methylguanine DNA-methyltransferase (MGMT) activity and DNA mismatch repair (MMR)-deficiency). Synergistic responses were observed when cells were exposed to cannabinoids and imidazotetrazine agents. Synergy was increased with T25 and 4’-F-CBD. OrbiSIMS analysis highlighted the presence of methylated-DNA, a previously unknown anti-cancer mechanism of action of CBD. Conclusions This work demonstrates the anti-cancer activity of 4’-F-CBD and the synergy of cannabinoids with imidazotetrazine agents for the first time and expands understanding of CBD mechanism of action.
The use of Δ8-tetrahydrocannabinol (Δ8-THC) has increased in recent years. Given that the oral absorption of cannabinoids in oil formulations is typically slow and variable, nanoemulsions may be an improved delivery vehicle. Therefore, we characterized the pharmacokinetics (PK) in Sprague-Dawley rats following the administration of three different oral formulations containing 10 mg/kg Δ8-THC: a translucent liquid nanoemulsion, a reconstituted powder nanoemulsion, and a medium chain triglyceride (MCT) oil solution for comparison. Δ8-THC was also administered intravenously at 0.6 mg/kg. Plasma samples were quantified for Δ8-THC and two metabolites, 11-hydroxy-Δ8-THC (11-OH-Δ8-THC) and 11-carboxy-Δ8-THC (COOH-Δ8-THC). Non-compartmental PK parameters were calculated, and a PK model was developed based on pooled data. Despite a smaller median droplet size of the translucent liquid nanoemulsion (26.9 nm) compared to the reconstituted powder nanoemulsion (168 nm), the PK was similar for both. The median Tmax values of Δ8-THC for the nanoemulsions (0.667 and 1 h) were significantly shorter than the median Tmax of Δ8-THC in MCT oil (6 h). This resulted in an approximately 4-fold higher Δ8-THC exposure over the first 4 h for the nanoemulsions relative to the MCT oil solution. The active 11-OH-Δ8-THC metabolite followed a similar pattern to Δ8-THC. The non-compartmental bioavailability estimates of Δ8-THC for the nanoemulsions (11–16.5%) were lower than for the MCT oil solution (>21.5%). However, a model-based analysis indicated similar bioavailability for all three oral formulations. These results demonstrate favorable absorption properties of both nanoemulsions, despite the difference in droplet sizes, compared to an MCT oil formulation.
Working memory is an executive function that orchestrates the use of limited amounts of information, referred to as working memory capacity, in cognitive functions. Cannabis exposure impairs working memory in humans; however, it is unclear if Cannabis facilitates or impairs rodent working memory and working memory capacity. The conflicting literature in rodent models may be at least partly due to the use of drug exposure paradigms that do not closely mirror patterns of human Cannabis use. Here, we used an incidental memory capacity paradigm where a novelty preference is assessed after a short delay in spontaneous recognition-based tests. Either object or odor-based stimuli were used in test variations with sets of identical (IST) and different (DST) stimuli (3 or 6) for low- and high-memory loads, respectively. Additionally, we developed a human-machine hybrid behavioral quantification approach which supplements stopwatch-based scoring with supervised machine learning-based classification. After validating the spontaneous IST and DST in male rats, 6-item test versions with the hybrid quantification method were used to evaluate the impact of acute exposure to high-THC or high-CBD Cannabis smoke on novelty preference. Under control conditions, male rats showed novelty preference in all test variations. We found that high-THC, but not high-CBD, Cannabis smoke exposure impaired novelty preference for objects under a high-memory load. Odor-based recognition deficits were seen under both low-, and high-memory loads only following high-THC smoke exposure. Ultimately, these data show that Cannabis smoke exposure impacts incidental memory capacity of male rats in a memory load-dependent, and stimuli-specific manner. Significance Statement Incidental memory refers to the limited amount of information encoded by chance during behavior. How psychoactive drug exposure affects incidental memory is poorly understood, particularly for Cannabis exposure. To address this question, we validated object- and odor-based spontaneous incidental memory tests in male rats using a novel human-machine hybrid scoring method. Using these tests, we show exposure to high-THC, but not high-CBD, Cannabis smoke impairs incidental memory under high-memory loads in object-based tests and both high- and low-memory loads in the odor-based tests. Our results highlight cannabinoid-specific effects on incidental memory in male rats using a validated Cannabis smoke exposure method, which have broad implications for the impacts of human use of Cannabis on cognition.
Cannabidiol (CBD) is on the rise as over-the-counter medication to treat sleep disturbances, anxiety, pain, and epilepsy due to its action on the excitatory/inhibitory balance in the brain. However, it remains unclear if CBD also leads to adverse effects on memory via changes of sleep macro- and microarchitecture. To investigate the effect of CBD on sleep and memory consolidation, we performed two experiments using the object space task testing for both simple and cumulative memory in rats. We show that oral CBD administration extended the sleep period but changed the properties of rest and non-REM sleep oscillations (delta, spindle, ripples). Specifically, CBD also led to less long (>100 ms) ripples and, consequently, worse cumulative memory consolidation. In contrast, simple memories were not affected. In sum, we can confirm the beneficial effect of CBD on sleep; however, this comes with changes in oscillations that negatively impact memory consolidation.
Introduction: Basic pharmacokinetic (PK) and pharmacodynamic models of the phytocannabinoids Δ-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) are critical for developing translational models of exposure and toxicity. The neonatal period is a particularly important time to study the effects of cannabinoids, yet there are few studies of cannabinoid PKs by different routes such as direct injection or breast milk ingestion. To study this question, we have developed a translationally relevant rodent model of perinatal cannabinoid administration by measuring plasma levels of THC and CBD after different routes and preparations of these drugs. Materials and Methods: Adult animals and pups were injected with THC or CBD either intraperitoneally or subcutaneously, and plasma was analyzed by liquid chromatography-tandem mass spectrometry to measure cannabinoid levels collected at specified intervals. We also tested the effect of preparation of the drug using an oil-based vehicle (sesame oil) and an aqueous vehicle (Tween). Finally, we measured the plasma levels of cannabinoids in neonatal pups that were transmitted through breast milk after intraperitoneal injection to nursing dams. Results: We observed differences in the PK profiles of cannabinoids in adults and neonatal pups that were dependent on the route of administration and type of vehicle. Cannabinoids prepared in aqueous vehicle, injected intraperitoneally, resulted in a high peak in plasma concentration, which rapidly decreased. In contrast, subcutaneous injections using sesame oil as a vehicle resulted in a slow rise and low plateau in plasma concentration. Intraperitoneal injections with sesame oil as a vehicle resulted in a slower rise compared with aqueous vehicle, but an earlier and higher peak compared with subcutaneous injection. Finally, the levels of THC and CBD that were similar to direct subcutaneous injections were measured in the plasma of pups nursing from intraperitoneally injected dams. Conclusions: The route of administration and the preparation of the drug have important and significant effects on the PK profiles of THC and CBD in rats. These results can be used to create different clinically relevant exposure paradigms in pups and adults, such as short high-dose exposure or a low-chronic exposure, each of which might have significant and varying effects on development.
Cannabidiol (CBD) has become a highly attractive entity in therapeutics. However, its low aqueous solubility, instability and handling problems limit the development of effective CBD formulations. Subcutaneously administered CBD-loaded polycaprolactone microparticles (MP) represent an interesting strategy to overcome these challenges. This work focuses on evaluating the pharmacokinetics of CBD formulated in polymer microparticles for subcutaneous administration and characterising its release. The mean release time (MRLT) parameter is used to compare the release of CBD from two microparticle formulations in vitro and in a mouse model. After the administration of CBD in solution, a bicompartmental distribution is observed due to the extensive diffusion to the brain, being the brain/blood AUC ratio 1.29. The blood and brain mean residence time (MRT) are 0.507 ± 0.04 and 0.257 ± 0.0004 days, respectively. MP prepared with two drug/polymer ratios (15/150-MP and 30/150-MP) are designed, showing similar in vitro dissolution profiles (similarity factor (f2) is 63.21), without statistically significant differences between MRLTin vitro values (4.68 ± 0.63 and 4.32 ± 0.05 days). However, considerable differences in blood and brain profiles between both formulations are detected. The blood and brain MRT values of 15/150-MP are 6.44 ± 0.3 days and 6.15 ± 0.25 days, respectively, whereas significantly lower values 3.91 ± 0.29 days and 2.24 ± 0.64 days are obtained with 30/150-MP. The extended release of CBD during 10 days after a single subcutaneous administration is achieved.
4-20% of people report using cannabis during pregnancy, thereby it is essential to assess the associated risks. There is some evidence that prenatal cannabis exposure (PCE) may be associated with increased risk for development of obesity and diabetes later in life, however this has not been well explored under controlled conditions. The aim of this study was to use a translational THC vapor model in rodents to characterize the effects of PCE on adiposity, glucose metabolism, and feeding patterns in adulthood, with focus on potential sex differences. Pregnant Sprague Dawley rats were exposed to vaporized THC (100mg/ml) or control (polyethylene glycol vehicle) across the entire gestational period. Adult offspring from PCE or control litters were subjected to measures of adiposity, glucose metabolism and feeding behavior. Rats were then placed onto special diets (60% high-fat diet [HFD] or control 10% low fat diet [LFD]) for 4-months, then re-subjected to adiposity, glucose metabolism and feeding behavior measurements. PCE did not influence maternal weight or food consumption but was associated with transient decreased pup weight. PCE did not initially influence bodyweight or adiposity, but PCE did significantly reduce the rate of bodyweight gain when animals were maintained on special diets (HFD/LFD), regardless of which diet. Further, PCE had complex effects on glucose metabolism and feeding behavior that were both sex and diet dependent. No effects of PCE were found on plasma leptin or insulin, or white adipose tissue mass. Overall, this data enhances current understanding of the potential impacts of PCE.
Chronic neuropathic pain is a debilitating pain syndrome caused by damage to the nervous system that is poorly served by current medications. Given these problems, clinical studies have pursued extracts of the plant Cannabis sativa as alternative treatments for this condition. The vast majority of these studies have examined cannabinoids which contain the psychoactive constituent delta‐9‐tetrahydrocannabinol (THC). While there have been some positive findings, meta‐analyses of this clinical work indicates that this effectiveness is limited and hampered by side‐effects. This review focuses on how recent preclinical studies have predicted the clinical limitations of THC‐containing cannabis extracts, and importantly, point to how they might be improved. This work highlights the importance of targeting channels and receptors other than cannabinoid CB1 receptors which mediate many of the side‐effects of cannabis. image
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Sativex(®), a cannabis extract oromucosal spray containing Δ(9)-tetrahydrocannabinol (THC) and cannabidiol (CBD), is currently in phase III trials as an adjunct to opioids for cancer pain treatment, and recently received United Kingdom approval for treatment of spasticity. There are indications that CBD modulates THC's effects, but it is unclear if this is due to a pharmacokinetic and/or pharmacodynamic interaction. Cannabis smokers provided written informed consent to participate in this randomized, controlled, double-blind, double-dummy institutional review board-approved study. Participants received 5 and 15 mg synthetic oral THC, low-dose (5.4 mg THC and 5.0 mg CBD) and high-dose (16.2 mg THC and 15.0 mg CBD) Sativex, and placebo over 5 sessions. CBD, THC, 11-hydroxy-THC, and 11-nor- 9-carboxy-THC were quantified in plasma by 2-dimensional GC-MS. Lower limits of quantification were ≤0.25 μg/L. Nine cannabis smokers completed all 5 dosing sessions. Significant differences (P < 0.05) in maximum plasma concentrations (C(max)) and areas under the curve from 0-10.5 h postdose (AUC(0→10.5)) for all analytes were found between low and high doses of synthetic THC and Sativex. There were no statistically significant differences in C(max), time to maximum concentration or in the AUC(0→10.5) between similar oral THC and Sativex doses. Relative bioavailability was calculated to determine the relative rate and extent of THC absorption; 5 and 15 mg oral THC bioavailability was 92.6% (13.1%) and 98.8% (11.0%) of low- and high-dose Sativex, respectively. These data suggest that CBD modulation of THC's effects is not due to a pharmacokinetic interaction at these therapeutic doses.
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This short communication examines the question whether the experimental data presented in a study by Merrick et al. are of clinical relevance. These authors found that cannabidiol (CBD), a major cannabinoid of the cannabis plant devoid of psychotropic effects and of great interest for therapeutic use in several medical conditions, may be converted in gastric fluid into the psychoactive cannabinoids delta-8-THC and delta-9-THC to a relevant degree. They concluded that “the acidic environment during normal gastrointestinal transit can expose orally CBD-treated patients to levels of THC and other psychoactive cannabinoids that may exceed the threshold for a positive physiological response.” They issued a warning concerning oral use of CBD and recommend the development of other delivery methods. However, the available clinical data do not support this conclusion and recommendation, since even high doses of oral CBD do not cause psychological, psychomotor, cognitive, or physical effects that are characteristic for THC or cannabis rich in THC. On the contrary, in the past decades and by several groups, high doses of oral CBD were consistently shown to cause opposite effects to those of THC in clinical studies. In addition, administration of CBD did not result in detectable THC blood concentrations. Thus, there is no reason to avoid oral use of CBD, which has been demonstrated to be a safe means of administration of CBD, even at very high doses.
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The evidence base for the use of medical cannabis preparations containing specific ratios of cannabidiol (CBD) and Δ(9)-tetrahydrocannabinol (THC) is limited. While there is abundant data on acute interactions between CBD and THC, few studies have assessed the impact of their repeated co-administration. We previously reported that CBD inhibited or potentiated the acute effects of THC dependent on the measure being examined at a 1:1 CBD:THC dose ratio. Further, CBD decreased THC effects on brain regions involved in memory, anxiety and body temperature regulation. Here we extend on these finding by examining over 15 days of treatment whether CBD modulated the repeated effects of THC on behaviour and neuroadaption markers in the mesolimbic dopamine pathway. After acute locomotor suppression, repeated THC caused rebound locomotor hyperactivity that was modestly inhibited by CBD. CBD also slightly reduced the acute effects of THC on sensorimotor gating. These subtle effects were found at a 1:1 CBD:THC dose ratio but were not accentuated by a 5:1 dose ratio. CBD did not alter the trajectory of enduring THC-induced anxiety nor tolerance to the pharmacological effects of THC. There was no evidence of CBD potentiating the behavioural effects of THC. However we demonstrated for the first time that repeated co-administration of CBD and THC increased histone 3 acetylation (H3K9/14ac) in the VTA and ΔFosB expression in the nucleus accumbens. These changes suggest that while CBD may have protective effects acutely, its long-term molecular actions on the brain are more complex and may be supradditive.
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Schizophrenia is a severe psychiatric disorder that involves positive, negative and cognitive symptoms. Prepulse inhibition of startle reflex (PPI) is a paradigm that assesses the sensorimotor gating functioning and is impaired in schizophrenia patients as well as in animal models of this disorder. Recent data point to the participation of the endocannabinoid system in the pathophysiology and pharmacotherapy of schizophrenia. Here, we focus on the effects of cannabinoid drugs on the PPI deficit of animal models of schizophrenia, with greater focus on the SHR (Spontaneously Hypertensive Rats) strain, and on the future prospects resulting from these findings.
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Introduction: In recent research, orally administered cannabidiol (CBD) showed a relatively high incidence of somnolence in a pediatric population. Previous work has suggested that when CBD is exposed to an acidic environment, it degrades to Δ⁹-tetrahydrocannabinol (THC) and other psychoactive cannabinoids. To gain a better understanding of quantitative exposure, we completed an in vitro study by evaluating the formation of psychoactive cannabinoids when CBD is exposed to simulated gastric fluid (SGF). Methods: Materials included synthetic CBD, Δ⁸-THC, and Δ⁹-THC. Linearity was demonstrated for each component over the concentration range used in this study. CBD was spiked into media containing 1% sodium dodecyl sulfate (SDS). Samples were analyzed using chromatography with UV and mass spectrometry detection. An assessment time of 3 h was chosen as representative of the maximal duration of exposure to gastric fluid. Results: CBD in SGF with 1% SDS was degraded about 85% after 60 min and more than 98% at 120 min. The degradation followed first-order kinetics at a rate constant of −0.031 min⁻¹ (R²=0.9933). The major products formed were Δ⁹-THC and Δ⁸-THC with less significant levels of other related cannabinoids. CBD in physiological buffer performed as a control did not convert to THC. Confirmation of THC formation was demonstrated by comparison of mass spectral analysis, mass identification, and retention time of Δ⁹-THC and Δ⁸-THC in the SGF samples against authentic reference standards. Conclusions: SGF converts CBD into the psychoactive components Δ⁹-THC and Δ⁸-THC. The first-order kinetics observed in this study allowed estimated levels to be calculated and indicated that the acidic environment during normal gastrointestinal transit can expose orally CBD-treated patients to levels of THC and other psychoactive cannabinoids that may exceed the threshold for a physiological response. Delivery methods that decrease the potential for formation of psychoactive cannabinoids should be explored.