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Pharmacokinetics of Cannabidiol, Cannabidiolic Acid, Δ9-Tetrahydrocannabinol, Tetrahydrocannabinolic Acid and Related Metabolites in Canine Serum After Dosing With Three Oral Forms of Hemp Extract

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Cannabidiol (CBD)-rich hemp extract use is increasing in veterinary medicine with little examination of serum cannabinoids. Many products contain small amounts of Δ9-tetrahydrocannabinol (THC), and precursor carboxylic acid forms of CBD and THC known as cannabidiolic acid (CBDA) and tetrahydrocannabinolic acid (THCA). Examination of the pharmacokinetics of CBD, CBDA, THC, and THCA on three oral forms of CBD-rich hemp extract that contained near equal amounts of CBD and CBDA, and minor amounts (<0.3% by weight) of THC and THCA in dogs was performed. In addition, we assess the metabolized psychoactive component of THC, 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC) and CBD metabolites 7-hydroxycannabidiol (7-OH-CBD) and 7-nor-7-carboxycannabidiol (7-COOH-CBD) to better understand the pharmacokinetic differences between three formulations regarding THC and CBD, and their metabolism. Six purpose-bred female beagles were utilized for study purposes, each having an initial 7-point, 24-h pharmacokinetic study performed using a dose of 2 mg/kg body weight of CBD/CBDA (~1 mg/kg CBD and ~1 mg/kg CBDA). Dogs were then dosed every 12 h for 2 weeks and had further serum analyses at weeks 1 and 2, 6 h after the morning dose to assess serum cannabinoids. Serum was analyzed for each cannabinoid or cannabinoid metabolite using liquid chromatography and tandem mass spectroscopy (LC-MS/MS). Regardless of the form provided (1, 2, or 3) the 24-h pharmacokinetics for CBD, CBDA, and THCA were similar, with only Form 2 generating enough data above the lower limit of quantitation to assess pharmacokinetics of THC. CBDA and THCA concentrations were 2- to 3-fold higher than CBD and THC concentrations, respectively. The 1- and 2-week steady-state concentrations were not significantly different between the two oils or the soft chew forms. CBDA concentrations were statistically higher with Form 2 than the other forms, showing superior absorption/retention of CBDA. Furthermore, Form 1 showed less THCA retention than either the soft chew Form 3 or Form 2 at weeks 1 and 2. THC was below the quantitation limit of the assay for nearly all samples. Overall, these findings suggest CBDA and THCA are absorbed or eliminated differently than CBD or THC, respectively, and that a partial lecithin base provides superior absorption and/or retention of CBDA and THCA.
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ORIGINAL RESEARCH
published: 04 September 2020
doi: 10.3389/fvets.2020.00505
Frontiers in Veterinary Science | www.frontiersin.org 1September 2020 | Volume 7 | Article 505
Edited by:
Nora Mestorino,
National University of
La Plata, Argentina
Reviewed by:
Jeremy Carlier,
Sapienza University of Rome, Italy
Cengiz Gokbulut,
Balikesir University, Turkey
*Correspondence:
Joseph J. Wakshlag
jw37@cornell.edu
Specialty section:
This article was submitted to
Veterinary Pharmacology and
Toxicology,
a section of the journal
Frontiers in Veterinary Science
Received: 07 May 2020
Accepted: 03 July 2020
Published: 04 September 2020
Citation:
Wakshlag JJ, Schwark WS,
Deabold KA, Talsma BN, Cital S,
Lyubimov A, Iqbal A and Zakharov A
(2020) Pharmacokinetics of
Cannabidiol, Cannabidiolic Acid,
19-Tetrahydrocannabinol,
Tetrahydrocannabinolic Acid and
Related Metabolites in Canine Serum
After Dosing With Three Oral Forms of
Hemp Extract. Front. Vet. Sci. 7:505.
doi: 10.3389/fvets.2020.00505
Pharmacokinetics of Cannabidiol,
Cannabidiolic Acid,
19-Tetrahydrocannabinol,
Tetrahydrocannabinolic Acid and
Related Metabolites in Canine Serum
After Dosing With Three Oral Forms
of Hemp Extract
Joseph J. Wakshlag 1
*, Wayne S. Schwark 2, Kelly A. Deabold 3, Bryce N. Talsma 3,
Stephen Cital 4, Alex Lyubimov 5, Asif Iqbal 5and Alexander Zakharov 5
1Department of Clinical Sciences, Cornell University College of Veterinary Medicine, Ithaca, NY, United States, 2Department
of Molecular Medicine, Cornell University College of Veterinary Medicine, Ithaca, NY, United States, 3University of Florida
Comparative Diagnostic and Population Medicine, Gainesville, FL, United States, 4Ellevet Sciences, Product Development
and Scientific Communications, Portland, ME, United States, 5Toxicology Research Laboratory, Department of
Pharmacology, College of Medicine, University of Illinois at Chicago, Chicago, IL, United States
Cannabidiol (CBD)-rich hemp extract use is increasing in veterinary medicine with
little examination of serum cannabinoids. Many products contain small amounts of
19-tetrahydrocannabinol (THC), and precursor carboxylic acid forms of CBD and
THC known as cannabidiolic acid (CBDA) and tetrahydrocannabinolic acid (THCA).
Examination of the pharmacokinetics of CBD, CBDA, THC, and THCA on three
oral forms of CBD-rich hemp extract that contained near equal amounts of CBD
and CBDA, and minor amounts (<0.3% by weight) of THC and THCA in dogs
was performed. In addition, we assess the metabolized psychoactive component
of THC, 11-hydroxy-19-tetrahydrocannabinol (11-OH-THC) and CBD metabolites
7-hydroxycannabidiol (7-OH-CBD) and 7-nor-7-carboxycannabidiol (7-COOH-CBD) to
better understand the pharmacokinetic differences between three formulations regarding
THC and CBD, and their metabolism. Six purpose-bred female beagles were utilized for
study purposes, each having an initial 7-point, 24-h pharmacokinetic study performed
using a dose of 2 mg/kg body weight of CBD/CBDA (1 mg/kg CBD and 1
mg/kg CBDA). Dogs were then dosed every 12 h for 2 weeks and had further serum
analyses at weeks 1 and 2, 6 h after the morning dose to assess serum cannabinoids.
Serum was analyzed for each cannabinoid or cannabinoid metabolite using liquid
chromatography and tandem mass spectroscopy (LC-MS/MS). Regardless of the form
provided (1, 2, or 3) the 24-h pharmacokinetics for CBD, CBDA, and THCA were similar,
with only Form 2 generating enough data above the lower limit of quantitation to
assess pharmacokinetics of THC. CBDA and THCA concentrations were 2- to 3-fold
higher than CBD and THC concentrations, respectively. The 1- and 2-week steady-state
Wakshlag et al. Canine Serum Cannabinoid Concentrations
concentrations were not significantly different between the two oils or the soft chew
forms. CBDA concentrations were statistically higher with Form 2 than the other forms,
showing superior absorption/retention of CBDA. Furthermore, Form 1 showed less THCA
retention than either the soft chew Form 3 or Form 2 at weeks 1 and 2. THC was below
the quantitation limit of the assay for nearly all samples. Overall, these findings suggest
CBDA and THCA are absorbed or eliminated differently than CBD or THC, respectively,
and that a partial lecithin base provides superior absorption and/or retention of CBDA
and THCA.
Keywords: dog, hemp, cannabidiol, cannabidiolic acid, tetrahydrocannabinol, tetrahydrocannabinolic acid,
pharmacokinetics
INTRODUCTION
The use of cannabidiol (CBD)-rich hemp-extract supplements
is increasing in companion animal medicine with very few
publications on the efficacy of these products in clinical
conditions. To date, there are only three clinical publications
with positive outcomes in canine osteoarthritis and epilepsy (1
3). Two publications have also examined the pharmacokinetics of
similar dosing at 2 mg/kg of cannabinoids from hemp products
(1,4). Both the osteoarthritis study BID dosing of 2 and 2.5 mg/kg
in the seizure study were used, while the third study was a non-
placebo controlled study showing efficacy in a dose escalation
once per day of cannabinoids between 1.5 and 2.5 mg/kg, with
CBD representing the primary cannabinoid in this hemp extract
study (13). Further work on absorption at the 2 mg/kg dose
using a CBD and cannabidiolic acid (CBDA) mixture at 50%
of each in a soft chew form [maximum serum concentration
(Cmax) 300 ng/mL CBD] showed superior absorption when
compared to prior data using an oil base (Cmax 100 ng/mL
CBD), providing some evidence along with others that dosing
with food may be advantageous (4,5).
With the measurement of serum CBD now published in
canines conjures a presumption that CBDA may undergo
biotransformation to CBD based on a single human study
(6). In-vitro systems of gastric absorption suggest that CBDA
might become CBD in the gastrointestinal tract and that
CBD has the potential to become 19-tetrahydrocannabinol
(THC) through either gastric or hepatic conversion (7,8).
Currently, there is little evidence of this occurrence in vivo,
but in general it is thought that CBD does not become THC
in vivo (9). Conversely, literature has shown that providing
oral CBDA rather than CBD, actually results in a 3-fold
higher Cmax of CBD in the bloodstream of people (6). This
has led to the idea that CBDA may be a more bioavailable
cannabinoid that becomes CBD in vivo or that it might
help with the absorption of CBD, allowing for higher serum
concentrations with lower dosing (6). To date, there has been
Abbreviations: CBD, Cannabidiol; CBDA, Cannabidiolic Acid; 7-OH-CBD,
7-Hydroxycannabidiol; 7-COOH-CBD, 7-Nor-7-carboxycannabidiol; CBG,
Cannabigerol; CBN, Cannabinol; THC, (-)-19-Tetrahydrocannabinol; THCA,
19-Tetrahydrocannabinolic Acid; 11-OH-THC, (±)-11-Hydroxy-19-THC;
COOH-THC-Glu, (+)-11-nor-9-Carboxy-19-THC glucuronide.
little examination of serum CBDA in any species to prove
this postulation.
In conjunction with using CBDA to improve absorption or
retention of CBD, current literature is suggesting that CBD
absorption is enhanced by 3- to 5-fold when providing it
in conjunction with a fatty meal (5,1014). The current
recommendations for Epidiolex, the FDA-approved human CBD
product, is that it be fed with a meal to enhance absorption (12).
Our prior publication in dogs showed that providing CBD in a
soft chew food matrix improved absorption with higher CBD
maximal concentrations providing further evidence that a food
matrix might improve absorption but may lower retention times
and half-life times in dogs (4).
Nearly all of the hemp-related products being utilized in the
supplement market, including some labeled as CBD isolates, have
varying levels of THC and tetrahydrocannabinolic acid (THCA),
and although the THC and THCA levels are often below 0.3% by
weight, there may be absorption of these cannabinoids, which are
psychotropic and neuroprotective, respectively (1517). The idea
that THC may become 11-hydroxy-19-tetrahydrocannabinol
(11-OH-THC), the primary intoxicating form, in significant
amounts enabling it to induce clinical signs in dogs is concerning.
Only preliminary research has been done evaluating THC and
11-OH-THC concentrations in dogs being given oral hemp
extracts, with none evaluating THCA forms (17). This concern,
in line with the known enhanced uptake of THC with food in
general, creates a real conundrum for veterinarians concerning
the safety of providing small amounts of THC and its derivatives
when using complete spectrum hemp plant extracts (12,18). In
addition, prior clinical studies have identified rises in hepatic
enzymes, more specifically ALP, during oral hemp extract
administration; and in normal healthy dogs being provided 10
mg/kg and above of CBD or CBD-rich hemp extracts (1,2,
19). Further clarity is necessary regarding hepatic effects during
typical dosing regimens currently being used.
The aim of our study was 4-fold: (1) provide pharmacokinetic
information on a hemp extract with known CBD and CBDA
concentrations and to examine whether low THC and THCA
concentrations could be detected when fed in three oral food-
based forms using 24-h pharmacokinetic profiling as well as
1- and 2-week average serum concentrations; (2) elucidate the
gastrointestinal absorption kinetics of CBDA and potentially
THCA; (3) determine whether we could detect 11-OH-THC, the
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
major intoxicating metabolite of THC, and 7-OH-CBD and 7-
COOH-CBD as primary metabolites of CBD in human literature;
and (4) examine the serum biochemical indicators of hepatic
function before and after 2 weeks of twice-daily dosing to ensure
that the liver is not affected by these particular forms at the 2
mg/kg dosing regimen.
MATERIALS AND METHODS
Dogs
Six purpose-bred intact female beagles between the ages of 14
and 18 months were acquired and housed under an Institutional
Animal Care and Use Committee approved protocol at the
University of Florida (2019-0024). The dogs were acclimated
to the environment for 2 weeks and had initial bloodwork
and physical examinations done by the Animal Care Service
Veterinarians before beginning the study. All of the dogs were
between 8.4 and 9.7 kg for the duration of the study. The dogs
were weighed weekly to assess relative dosing with the three
different forms of an oral cannabinoid-rich hemp product. After
each 2-week phase of investigation, the dogs were provided a
3-week wash-out period before the next phase of study began.
The first phase of study was with a mixed medium/long-chain
triglyceride oil (Form 1); the second phase of study was with a
lecithin and sesame oil base (Form 2). The third phase of study
was done by providing a chewable form (Form 3). All dogs were
fed 100 g of wet dog food immediately after administration of the
form being studied at each dosing.
Hemp Extract Vehicles
Three different forms of the same hemp extract (ElleVet Sciences,
Portland, ME) were utilized in the study with Form 1 (Oil A)
being a mix of 25% medium-chain triglycerides (Perfect Keto
100% MCT, Austin, TX) and 75% long-chain triglyceride-based
organic sesame oil (Jedwards International Inc, Braintree, MA).
Each milliliter of the oil contained 28 mg of CBD, 29 mg of
CBDA, 1 mg of THC, 0.8 mg THCA, 0.7 mg of cannabigerolic
acid (CBGA), and 1.3 mg of cannabichromene (CB C) proven
with third-party analysis by a certified ISO/IEC 17025 Laboratory
(ProVerde Laboratory, Milford, MA). Form 2 (Oil B) was exactly
the same regarding cannabinoid concentration except that 25%
of the base oil was from sunflower lecithin (NOW Sunflower
Lecithin, Bloomingdale, IL), and the remaining 75% was the same
organic sesame oil as Form 1. Form 3 was formulated with the
same hemp extract to contain 5 mg of CBDA and 5 mg of
CBD in each soft chew with a similar profile as stated above.
For consistency of dose across dogs, each dog was provided two
chews of Form 3 every 12 h because more exact dosing in mg/kg
was impractical; therefore, the dogs were receiving between 2.0
and 2.3 mg/kg body weight for this particular product. The
manufacturing of Form 3 was done using a cold extrusion
process after reconstitution of a dough-like consistency using a
materials base of peanut butter, glycerin, defatted rice bran, water,
molasses dry (cane), glucosamine HCL, dextrose (glucose-dry),
sweet potato (powder), hemp oil, brewer’s yeast (dehydrated),
potato starch, guar gum, rice starch, dehydrated peanut butter,
and sorbic acid, in descending order based on weight based on
good manufacturing practices.
Dosing, Blood Draw, and Health
Evaluations
The dogs underwent a 24-h pharmacokinetic (PK) assessment
with blood draws at 0, 1, 2, 4, 8, 12, and 24 h, with twice-a-day
dosing starting the following morning of the 24-h PK experiment
with daily dosing (0.4 mL of oil using a 1 cc syringe or two soft
chews) at 7 am and 6 pm for the duration of each phase of the
study (2 weeks). For the 24-h PK assessment, dogs had 4 mL of
blood drawn from the jugular or cephalic vein using a 20-gauge
needle, which was then placed in a red top coagulation tube and
allowed to clot before centrifugation at 3,600 g for 10 min. Serum
was collected and immediately frozen at 80C. At the end of
weeks 1 and 2 of twice-daily dosing, dogs were provided their 7
am dose and then had a follow-up blood draw 6 h after dosing to
assess mean serum concentration at the halfway point between
doses. The dogs also had initial blood draws prior to starting
the trial at 6 a.m. on their first day of each arm of the trial, and
6 h after their last 2-week dose to assess serum hepatic enzymes
due to prior reports of elevated liver enzymes with daily exposure
to hemp-based extracts (1,2). Dogs were evaluated daily during
play time by the staff and were asked to report any somnolence,
lethargy, gait abnormalities, ataxia, or behavioral issues.
Serum hepatic biochemical analyses were performed at two
time points during the study. A background and a steady
state 2-week blood draw were collected to evaluated hepatic
function looking at albumin, alanine amino transferase (ALT),
alkaline phosphatase (ALP), aspartate aminotransferase (AST),
total bilirubin, glucose, and cholesterol (Antech Diagnostics,
Irvine, CA).
Serum Cannabinoid Analysis
Samples were batched within 8 weeks of the end of
experimentation on each form and were transported overnight
on dry ice to the laboratory for analysis. Cannabinoids
analysis was performed by a novel developed method allowing
simultaneous measurement of 10 cannabinoids and their
metabolites at the Toxicology Research Laboratory, University
of Illinois at Chicago. Reference standards for CBD and CBDA
were obtained from Restek Corporation (Bellefonte, PT); all
other reference and internal standards mentioned below were
obtained from Cerilliant Corporation (Round Rock, TX). The
concentration of cannabinoids (CBD, CBDA, THC, THCA,
CBN, and CBG) and their metabolites (11-OH-THC, 7-OH-
CBD, 7-COOH-CBD, and COOH-THC-Glu) in dog serum was
determined by high-performance LC-MS/MS (Nexera X2 and
LCMS 8050, Shimadzu Corp., Kyoto, Japan).
Dog serum (40 µL) was mixed with 20 µL of internal
standards [100 ng/mL of CBD-d3, THC-d3, 11-OH-THC-d3,
and 7-OH-CBD-d5 in water:methanol (50:50)] in a 96-well plate.
Proteins were precipitated, and compounds were extracted by
adding 80 µL of ice-cold acetonitrile to each sample followed
by vortexing (1–2 min) and centrifugation at 4,000 rpm for
10 min at 4C. The supernatants (100 µL) were mixed with water
(100 µL) in another 96-well plate and centrifuged again. The
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
processed samples were injected (10 µL) into Waters Atlantis T3
HPLC column (3 µm 2.1 ×50 mm) coupled to LC-MS/MS. The
column was equilibrated with mobile phase A (0.1% formic acid
in water) and mobile phase B (acetonitrile) at ratio A: B 50:50
for 0.5 min. The compounds were eluted by a linear gradient
from 50% B to 100% B over 6 min, and then held at 100%
B for 1 min. Subsequently, the column was re-equilibrated at
initial composition for 0.5 min at a flow rate of 0.3 mL/min. An
autosampler and column temperature were set at 4 and 30C,
respectively. CBD, CBDA, THC, THCA, CBN, CBG, and 11-
OH-THC were detected in electrospray ionization positive mode
using transitions m/z 314.90 >193.10, 359.10 >219.10, 315.00
>193.10, 359.00 >219.05, 311.10 >2 23.10, 316.90 >193.10,
and 331.50 >313.25 at retention times of 4.3, 4.0, 5.3, 5.8,
5.0, 4.3, and 3.3 min, respectively (Figure 1). In addition, 7-OH-
CBD, 7-COOH-CBD, and COOH-THC-Glu were detected in ESI
negative mode using multiple reaction monitoring transitions
m/z 329.20 >261.20, 343.30 >299.10, and 519.05 >343.30 at
retention times of 2.3, 2.2, and 2.0 min, respectively (Figure 1).
Interface voltage and temperature were 4 kV and 300C,
respectively. Desolvation line and heat block temperatures were
250 and 400C, respectively. Nebulizing, heating, and drying gas
flow were 2.7, 5, and 5 L/min, respectively.
Concentrations of cannabinoids were calculated by
LabSolutions software (Shimadzu Corp., Kyoto, Japan) using
a quadratic calibration curve with 1/c2weighing based on
relative response (peak area of cannabinoids/peak area of
internal standards). The calibration curve range was from 1 to
1,000 ng/mL for CBD, CBDA, THC, THCA, CBN, CBG, and
7-COOH-CBD, and from 2.5 to 1,000 ng/mL for 11-OH-THC,
7-OH-CBD, and COOH-THC-Glu in dog serum.
Pharmacokinetics and Statistical Analysis
The 24-h pharmacokinetic analysis for each cannabinoid or its
metabolite (CBD, CBDA, THC, THCA, CBG, CBN, 11-OH-
THC, 7-OH-CBD, 7-COOH-CBD, and COOH-THC-Glu) was
FIGURE 1 | A representative chromatogram of cannabinoids and their metabolites in fortified dog serum at upper limit of quantitation (1,000 ng/mL of each
compound). The compound name with corresponding Multiple Reaction Monitoring (MRM) transition and polarity is given in the inset of each chromatogram.
Dashed-line represents the diversion of MS detector for a particular MRM transition and time.
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
performed utilizing a commercial software system that allows
for a one compartment model using 5 half-life assumption for
mean serum concentration, which is reported (PK solutions
2.0, Summit PK, Montrose, CO). The results generated were
time to maximal concentrations (Tmax), maximum serum
concentration (Cmax), half-life (T½), area under the curve to
the last time point (AUC024), AUC of the dose extrapolated to
infinity (AUCinfin), mean retention time (MRT), and calculated
predicted 5 half-life mean serum concentration (Predict Ave).
All of these values and the standard error of the mean are
reported with follow-up statistics of each parameter being
completed using non-parametric statistics due to the small
sample sizes. Friedman’s testing with Dunn’s post-hoc analysis
was used to examine differences between the three groups
for each pharmacokinetic parameter that was performed. For
7-OH-CBD and 7-COOH-CBD, a Wilcoxon signed rank test
was used to assess Form 2 and Form 3 pharmacokinetics; as
methodological standards for 7-OH-CBD and 7-COOH-CBD
were not available, the time serum from Form 1 was analyzed.
To assess the 1- and 2-week serum cannabinoid concentrations
post 6 h dosing, a Friedman’s test was performed at each
week with Dunn’s post-hoc testing to assess difference between
groups at each week, except for 7-OH-CBD and 7-COOH-CBD
where differences between Form 2 and Form 3 were assessed
using a Wilcoxon signed rank test. A Wilcoxon signed rank
test was used to assess the weeks 1 and 2 results for each
cannabinoid examined. The hepatic serum chemistry data for
all parameters (albumin, AST, ALP, ALT, total bilirubin, glucose,
and cholesterol) at weeks 0 and 2 were performed using a
Wilcoxon signed rank test. All statistical measures utilized a
p-value of <0.05 to establish statistical significance, except for
the weeks 1 and 2 serum concentration data due to multiple
comparisons, hence p<0.025 was established after Bonferroni’s
corrections. All statistical testing was performed with Graphpad
Prism 6.0 (Graphpad, LaJolla, CA), and graphs were generated
by the same software or Microsoft Excel (Microsoft Inc.,
Redmond, WA).
RESULTS
Twenty-Four Hours Pharmacokinetics
No differences were noted for Tmax, T½, AUC024, AUCinfin,
MRT or predicted average concentration for all three oral forms
of the hemp product when examining CBD pharmacokinetics.
The only significant difference in CBD between the three oral
delivery forms was with the Form 3 appeared to have a higher
Cmax than Form 2, but not Form 1 (p=0.03, see Table 1).
CBDA pharmacokinetics showed no differences between any
of the forms for Cmax, Tmax, T½, AUC024, AUCinfin, MRT
or predicted average serum concentration (Table 1). THC
concentrations could not be compared over the 24-h time period
due to insufficient data for calculation of pharmacokinetics,
except for Form 2 which had sufficient data from all dogs to
report (Table 1). THCA, however, had ample absorption and
serum concentrations over time to assess the differences between
all forms showing the only difference in pharmacokinetics was
between the Forms 1 and 3 regarding MRT time being increased
with the chew (p=0.02; Table 1).
Due to the absence of the reference standards for 7-OH-CBD
and 7-COOH-CBD at the time of analysis of Form 1, it is not
possible to compare results for these compounds on this form
and the other formulations. The 7-COOH-CBD concentrations
could be compared between Form 2 and Form 3, and there were
no significant differences in any pharmacokinetic parameters
except for Cmax being slightly higher for Form 3 over Form 2 (p
=0.02; Table 1). Twenty-four-hour pharmacokinetic curves for
CBD, CBDA, THC, THCA, and 7-COOH-CBD are represented
in Figures 2A–C.
The metabolites of THC, 11-OH-THC, and COOH-THC-Glu
were all below the lower limit of quantitation (1 ng/mL for THC
or 2.5 ng/mL for 11-OH-THC and COOH-THC-Glu), except in
a few samples where 11-OH-THC was observed at 1 or 2 h (six
samples Form 1, four samples Form 2, and two samples Form 3).
7-OH-CBD was undetectable in all samples assessed in Forms 2
and 3. Hence, 24-h pharmacokinetics analysis was not possible
for any of these metabolites.
One- and Two-Week Serum Cannabinoid
Concentrations
When examining the CBD concentrations in serum at weeks 1
and 2, Form 1 serum concentrations (mean ±SEM) were 79 ±
9 ng/mL and 94 ±14 ng/mL at weeks 1 and 2. Form 2 serum
concentrations (mean ±SEM) were 129 ±10 ng/mL and 122
±10 ng/mL at weeks 1 and 2. Form 3 serum concentrations
(mean ±SEM) were 115 ±28 ng/mL and 60 ±9 ng/mL at
weeks 1 and 2, respectively. There were no statistically significant
differences between CBD concentrations between the weeks of
exposure or between the different formulations at the two time
points (Figure 3A).
CBDA serum concentrations were similar to CBD
concentrations at weeks 1 and 2. Form 1 serum concentrations
(mean ±SEM) were 75 ±21 ng/mL and 44 ±8 ng/ml at weeks 1
and 2. Form 2 serum concentrations (mean ±SEM) were 192 ±
36 ng/mL and 196 ±42 ng/mL at weeks 1 and 2. Form 3 serum
concentrations (mean ±SEM) were 52 ±12 ng/mL and 44 ±
10 ng/mL at weeks 1 and 2, respectively. Statistically, the serum
concentrations of CBDA at both weeks 1 and 2 were significantly
higher for Form 2 when compared to Forms 1 and 3 (p<0.01;
Figure 3B). When assessing CBD and CBDA across weeks 1 and
2, there were no significant differences in concentrations across
any of the formulations, proving relatively similar concentrations
over weeks 1 and 2.
THC serum concentrations were far lower than CBD or
CBDA concentrations following similar absorption kinetic of
CBD. Form 1 serum concentrations (mean ±SEM) were 2.7
±0.5 ng/mL and 2.9 ±0.7 ng/mL at weeks 1 and 2. Form
2 serum concentrations (mean ±SEM) were 5.2 ±0.4 ng/mL
and 4.4 ±0.5 ng/mL at weeks 1 and 2. Form 3 serum
concentrations were 3.9 ±1.2 ng/mL and 1.7 ±0.4 ng/mL
at weeks 1 and 2, respectively (Figure 3C). No significant
differences in concentrations were found between the three
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
TABLE 1 | Mean and SEM (n=6 for all cannabinoids) on serum 24- pharmacokinetics values of CBD, CBDA, THC, THCA, and 7-COOH-CBD.
CBD (ng/mL) Cmax Tmax T1/2 AUC024 AUCinfin MRT Predict Ave
Form 1 145 ±69 1.5 ±0.5 4.1 ±0.7 635 ±399 656 ±414 5.2 ±1.4 53 ±33
Form 2 124 ±62 2.0 ±1.1 4.4 ±1.4 683 ±146 707 ±144 6.5 ±2.1 63 ±17
Form 3 226 ±89* 2.5 ±1.2 3.8 ±0.3 826 ±74 845 ±74 5.3 ±1.4 70 ±15
CBDA (ng/mL)
Form 1 383 ±167 1.0 ±0.0 4.4 ±2.7 1,018 ±308 1,152 ±451 5.2 ±3.3 88 ±41
Form 2 386 ±213 1.2 +0.4 4.2 ±1.0 1,619 ±898 1,748 ±855 6.8 ±2.3 136 ±66
Form 3 510 ±350 2.3 +0.6 2.4 ±1.1 1,407 ±585 1,419 ±591 4.3 ±1.5 191 ±158
THC (ng/mL)
Form 1 BQL BQL BQL BQL BQL BQL BQL
Form 2 6 ±3 1.7 ±0.5 4.0 ±3.9 22 ±9 27 ±9 6.3 ±5.7 3.0 ±0.5
Form 3 BQL BQL BQL BQL BQL BQL BQL
THCA (ng/mL)
Form 1 35 ±14 1.7 ±1.2 6.5 ±5.1 171 ±57 209 ±89 9.8 ±7.6 18 ±6
Form 2 27 ±21 2.2 ±1.0 5.9 ±2.5 256 ±114 291 ±119 8.7 ±3.7 25 ±10
Form 3 45 ±25 3.3 ±1.0#3.9 ±0.6 212 ±69 223 ±71 6.6 ±1.725 ±5
7-COOH-CBD (ng/mL)
Form 1 NA NA NA NA NA NA NA
Form 2 13 ±2 5.0 ±0.7 8.4 ±2.1 159 ±36 168 ±41 9.4 ±1.0 19 ±4
Form 3 21 ±2** 5.3 ±0.8 4.8 ±0.4 188 ±19 196 ±22 8.8 ±0.7 24 ±2
*Indicates a statistically different mean Cmax (p <0.05) than the other groups for CBD. **Indicates a statistically different mean (p <0.05) than the other group for 7-COOH-CBD.
Indicates a significant difference between Form 1 and 3 (p <0.05).
Cmax, Maximal concentration.
Tmax, Time to a maximal concentration.
T½, Half-life.
AUC024, Area under the curve 24 h.
AUCinfin, Area under the curve extended to infinity.
MRT, Mean retention time.
Predict Ave, Predicted 5 half-life average concentration.
NA, Not Available.
BQL, Below Quantitation Limit.
different formulations at each time point nor between the weeks
1 and 2 time points.
THCA serum concentrations were higher than THC
concentrations and appear to follow kinetics of CBDA absorption
and retention. Form 1 serum concentrations (mean ±SEM)
were 10.4 ±1.2 ng/mL and 7.0 ±1.0 ng/mL at weeks 1 and
2. Form 2 serum concentrations (mean ±SEM) were 23.5
±22.0 ng/mL and 25.0 ±2.2 ng/mL at weeks 1 and 2. Form
3 serum concentrations were 25.0 ±3.0 ng/mL and 20.0 ±
2.2 ng/mL at weeks 1 and 2, respectively. Both Form 2 and
Form 3 had significantly higher THCA concentrations than
Form 1 at both weeks 1 and 2 (p<0.01; Figure 3D). There
were no significant differences found between weeks 1 and
2 of dosing.
Except for a few samples, COOH-THC-Glu was not detectable
in the bloodstream during weeks 1 and 2 testing. 11-OH-THC
levels were below the quantitation limit for Form 1, while Form
2 showed two of the six dogs having detectable levels at 2.6
and 6.4 ng/mL at week 1; and three of the six dogs showing
detectable concentrations at 4.0, 2.7, and 6.7 ng/mL at week 2.
Form 3 showed only one dog at week 2 having an 11-OH-
THC concentration higher than the lower limit of quantitation
at 2.8 ng/mL.
The CBD metabolites assessed at weeks 1 and 2 across all
three oral formulations showed no 7-OH-CBD accumulation
in dog serum, with all samples being below the lower
limit of quantitation. 7-COOH-CBD concentrations were not
determined in Form 1 due to lack of standards at the time of
analysis, but 7-COOH-CBD concentrations in Form 2 across the
six dogs were 24.5 ±2.3 ng/mL and 26.1 ±2.9 ng/mL at weeks
1 and 2, respectively. Serum concentrations of 7-COOH-CBD
when using Form 3 were 27.9 ±4.8 ng/mL at week 1, and 23.7
±4.7 ng/mL at week 2. There were no significant differences
between weeks 1 and 2 for either dosing form, and no differences
in concentrations were observed between the oral forms at each
time point.
Liver Biochemical Analysis and Dog Health
The major enzymes associated with hepatic injury or altered
function include ALP, ALT, and AST. We did not observe
any significant changes in any of the oral treatments in the
serum concentrations of these enzymes prior to beginning of
treatment and 2 weeks into twice-daily treatment (Table 2).
Serum albumin and cholesterol, which are other parameters
of hepatic function, also showed no significant changes due
to dosing over the 2-week period (Table 2). Assessment of
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
FIGURE 2 | Seven-point 24-h pharmacokinetics of three oral hemp-based forms showing oral absorption kinetics (mean and SEM) of cannabidiol (CBD-blue),
cannabidiolic acid (CBDA-red), 19-tetrahydrocannabinol (THC-green), tetrahydrocannabinolic acid (THCA-purple), and 7-carboxy- cannabidiol (7-COOH-CBD- light
blue for Form 2 and Form 3 only). (A) Oral absorption using 25% MCT/75% sesame oil base at 2 mg/kg dosing using a 50 mg/mL hemp cannabinoid preparation
(Form A); (B) oral absorption using 25% sunflower lecithin/75% sesame oil base at 2 mg/kg dosing using a 50 mg/mL hemp cannabinoid preparation (Form 2); and
(C) oral absorption using a 10 mg hemp cannabinoid/10 g chew (Form 3) at 2–2.3 mg/kg body weight.
biliary stasis as measured by total bilirubin shows no significant
rises or decreases over the 2-week time period regardless of
treatment group (Table 2). Daily assessment of the dogs by the
laboratory and animal care personnel showed no abnormalities
in behavior or health problems associated with hemp
extract administration.
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
FIGURE 3 | One- and two-week serum cannabinoids concentrations (mean and SEM) 6 h after morning dosing when using Form 1, Form 2, or Form 3 for oral
dosing. (A) Serum CBD concentrations. No significances noted between formats or times; (B) serum CBDA concentrations. *Indicates a significant increase in serum
CBDA concentrations for Form 2 as weeks 1 and 2 when compared to Form 1 and Form 3 (p<0.01); (C) serum THC concentrations. No significances noted
between formats or times; and (D) serum THCA concentrations. *Indicates a significant decrease in THCA with Form 1 when compared to Form 2 and Form 3 at both
weeks 1 and 2 (p<0.01).
TABLE 2 | Mean and standard error of the mean concentrations (n=6) for hepatic biochemistry including ALP, ALT, AST, albumin, total bilirubin, cholesterol, and glucose
at 0 and 2 weeks (wk).
Parameter (Ref. Range) Form 1–0 wk Form 1–2 wk Form 2–0 wk Form 2–2 wk Form 3–0 wk Form 3–2 wk
ALP (8–114 U/L) 39 ±3 46 ±5 37 ±4 40 ±4 32 ±4 35 ±5
ALT (18–64 U/L) 25 ±1 23 ±1 26 ±2 25 ±2 26 ±3 29 ±4
AST (15–52 U/L) 27 ±2 24 ±1 25 ±2 23 ±1 24 ±2 26 ±2
Albumin (2.9–3.8 g/dL) 3.1 ±0.5 3.1 ±0.3 3.1 ±0.1 3.0 ±0.1 3.3 ±0.1 3.4 ±0.1
Total Bilirubin (0.1–0.4 mg/dL) 0.2 ±0.1 0.2 ±0.1 0.2 ±0.0 0.2 ±0.0 0.2 ±0.0 0.2 ±0.0
Cholesterol (124–334 mg/dL) 210 ±10 250 ±29 199 ±22 223 ±19 211 ±20 226 ±19
Glucose (79–120 mg/dL) 91 ±4 105 ±6 100 ±3 89 ±6 102 ±2 91 ±9
ALP, alkaline phosphatase; ALT, alanine aminotransferase; AST, aspartate aminotransferase.
No significant differences were noted between time points for any treatment group.
DISCUSSION
This is the first pharmacokinetic serum assessment of
cannabinoids and major metabolites using a whole hemp
plant derived extract in dogs, most notably for the major
cannabinoid acid forms, CBDA and THCA, which are not
routinely assessed. The increase in oral use of whole hemp
extract in veterinary and human medicine warrants further
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
investigation into the native acid derivatives of CBD and THC,
since existing products that do not undergo heat extraction will
contain CBDA and THCA. In much of the prior research on
inhaled forms of cannabis, these derivatives were not assessed
since the heat-induced decarboxylation of CBDA to CBD and
THCA to THC (5,20). In the human literature, there is very
little investigation into CBDA, and it was previously thought that
when providing CBDA it either improved the absorption of CBD
or rapidly became CBD due to potential for gastric or hepatic
conversion (6,7). Our data shows that the absorption of CBDA
does occur in dogs and is absorbed at least twice as well as CBD
in 24-h kinetic examination. One limitation of our study design
is that we did not do more frequent sampling at 15 and 30 min
post-dosing, as it is entirely possible that we missed the Cmax
and Tmax for the cannabinioids, particularly since CDBA Cmax
is at our first sampling time point. It is unlikely that we missed
the Cmax or Tmax for CBD and THC since recent work in the
fed canine model shows similar results to ours with Tmax in
the 1–2 h range (21); however, the only other pharmacokinetics
examining CBDA in humans with more frequent sampling in a
fasted model suggesting 0.8–1 h to be the Tmax (22). Therefore,
future experiments for CBDA should incorporate these earlier
time points in fed or fasted models.
The pharmacokinetics of CBDA over a 2-week period
shows nearly equal serum concentrations to CBD, suggesting
absorption and retention of oral dosing. More interestingly, is
that Form 2, which contains a 25% sunflower lecithin base,
showed slightly higher AUC024 and mean retention time in
24-h pharmacokinetics, which may have translated into the
significantly higher weeks 1 and 2 serum concentrations when
compared to Form 1 (25% medium chain triglyceride base) or
Form 3. The implications of this are unknown from a clinical
perspective; however, CBDA may have some unique properties
as an anti-inflammatory as well the ability to mitigate nausea
through 5HT 1a receptor activation (2327). CBDA pharma-
biological understanding is in its infancy, but it may have equal,
if not better absorption when compared to CBD which is worth
further investigation.
This investigation is the first of its kind to assess both THC
and THCA as minor cannabinoids that are found in most CBD-
rich hemp products at lower than 0.3% combined. The quantity
of THC and THCA delivered to these dogs was <0.1 mg/kg
body weight, which is far lower than prior long-term dosing
(25 mg/kg) that resulted in minimal clinical side effects (28).
In the prior 52-week study, dogs became habituated to these
larger doses and exhibited THC serum concentrations in the
tens of ng/mL while our THC concentrations were within 2–
5 ng/mL regardless of the form used (28). In addition, no side
effects such as ataxia or somnolence was observed in the beagles
used in our study at any point during treatment. Interestingly,
the THCA concentrations in the dogs were noticeably higher
in the 10–25 ng/mL range at weeks 1 and 2 with slightly better
retention of THCA in Form 2 and Form 3 treated groups.
THCA appearance in the bloodstream at these concentrations
may be of therapeutic value since THCA has been suggested to
be a non-intoxicating and a neuroprotective cannabinoid, but
research into THCA is relatively sparse (15,29,30). It must also
be recognized that these exploratory investigations into canine
serum cannabinoids are not validated procedures (1,4,17,21).
Although R2values of 0.98 were achieved for all cannabinoids
when examining goodness of fit calculations, and the accuracy of
75% of calibration standards was within ±15% of the nominal
concentrations in our study, there may be higher inconsistencies
at data points particularly when many of THC cannabinoids
measured were near the lower limit of quantitation (due to very
low THC concentrations in the initial formulation products),
except for THCA.
Not surprisingly, the 11-OH-THC metabolite, which has been
associated with intoxicating effects, showed variable measurable
quantities in the 24-h pharmacokinetic profile and could not be
universally detected in all dogs at multiple time points, which did
not allow for 24-h pharmacokinetic analysis. However, weeks 1
and 2 concentrations were above the lower limit of quantitation
(2.5 ng/mL) in a few dogs on Form 2 (n=3) and Form 3
(n=1) with a range of 2.6–6.7 ng/mL. The only other long-
term canine assessment of 11-OH-THC suggests that dogs can
have concentrations between 6 and 46 ng/mL in their serum and
not display outward clinical side effects (26). Humans with 11-
OH-THC concentrations in the 2–20 ng/mL concentrations will
begin to exhibit cognitive and recall issues when tested without
any physiological changes (31,32). These disparities suggest
the possibility of species-dependent sensitivities and metabolism,
particularly in light of the evidence that dogs, rats, and humans
metabolize CBD and THC differently (33,34), and due to the
insufficient sensitivity of our assay in detecting 11-OH-THC,
other methods are necessary to truly evaluate this metabolite
(and/or dosing with higher THC levels may be used). The
THCA serum concentrations were higher than expected for all
forms of treatment when compared to the THC concentrations,
yet the mean retention time for THCA was 70–100% longer
than other cannabinoids, which might allow for slightly higher
bioaccumulation. Furthermore, we cannot rule out whether
THCA is metabolized to THC or eventually to 11-OH-THC,
which may be the reasons the occasionally higher 11-OH-THC
than THC that was encountered sporadically, though unlikely.
From a metabolic perspective, the metabolism of CBD was
also interrogated by assessing the major metabolites identified
in humans (7-OH-CBD and 7-COOH-CBD), which are not
prevalent in dogs. The levels of 7-OH-CBD could not be
measured in our dogs, while 7-COOH-CBD was in the 20–
30 ng/mL range as a mean concentration after 1 and 2 weeks
of use. These results are dramatically higher than what was
recently observed in a study where dogs received 62 mg/kg
in a short-term study, suggesting that there may be some
adaptation to CBD metabolism or differences in absorption
and retention in this study (17). Comparatively, the 7-COOH-
CBD is about 1–2% of what has been observed in humans
when giving similar doses of CBD (35). This lack of 7-
hydroxylation or carboxylation has been observed previously
in comparative literature, highlighting that the metabolites are
likely to be different and may result in different pharmacological
effects across species, which has not been investigated (28). In-
vitro liver homogenate experiments and metabolite generation
suggest hydroxylation and/or glucuronidation at the 4 or 6
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Wakshlag et al. Canine Serum Cannabinoid Concentrations
position rather than the 7 position (33,34). If and when
standards for such metabolites are developed further, serum
analysis may reveal the primary metabolites in dogs, which are
currently unknown.
It must also be noted that our experimental design utilized
feeding at the time of administration to promote cannabinoid
absorption. These are not new findings since older literature
suggests that THC uptake is 3- to 4-fold greater in primates when
provided with a mixed meal in the form of a cookie (9). More
recent data in rats shows that a lipid-based excipient will increase
absorption 4-fold in rats (13). Prior work by our group, when
using an oil base in fasted dogs at 2 mg/kg body weight as an equal
mix of CBD and CBDA, showed a CBD Cmax of 100 ng/mL,
while other groups have published that 10 mg/kg body weight of
CBD resulted in a serum Cmax of 500–600 ng/mL (1,21). More
recent canine data regarding provision of 2 mg/kg as an equal
mix of CBD and CBDA in a soft chew showed serum Cmax of
300 ng/mL of CBD, further suggesting promotion of absorption
with a mixed-meal soft chew (4). The use of the soft chew matrix
may have produced the higher maximal concentrations observed;
however, these dogs were fasted before administration of the
soft chew with no follow-up feeding, which may have led to the
quickened half-life observed (4). The current study utilized oils
(Forms 1 and 2) or soft chews (Form 3) with a small mixed meal
(110 g of canned wet dog food), which showed similar Cmax,
Tmax, T½ life, and AUC for each form of treatment used; with
trends toward Form 3 showings slightly better absorption of
CBD in the pharmacokinetic models based on increased Cmax,
while Form 2 has the highest weeks 1 and 2 mean CBD and
CBDA concentrations.
The use of cannabinoid-rich hemp-based oils for health
and disease is in its infancy in human and veterinary clinical
medicine. CBD use is proving efficacious in seizure disorders,
multiple-sclerosis-based spasm and pain, oncologic side effects
of chemotherapy, with a more recent indication in anxiety
and schizophrenic disorders using single or twice-a-day dosing
between 5 and 20 mg/kg per day in humans (15,3638).
In veterinary medicine, three clinical studies have suggested
potential use of CBD-rich hemp oils in seizure and osteoarthritis
disorders in canines (1–3). The only side effects noted in these
studies were rises in the alkaline phosphatase enzyme presumably
due to hepatic cytochrome p450 enzyme upregulation. These
hepatic effects are observed rather universally at doses of 10
mg/kg or higher in dogs (19). The use of 2 mg/kg of a
CBD/CBDA-rich cannabinoid oil did show some modest rises in
ALP in a geriatric population (1). However, the current study, and
a prior study in healthy young beagles, have not shown any rises
in any enzymes outside of normal reference ranges associated
with the hepatobiliary system, signifying that the CBD-rich hemp
product used in this study at this concentration is likely to
be safe (4), particularly in light of the recent long-term GW
pharmaceutical study in dogs using 10–100 mg/kg of CBD daily
for 39 weeks proving safe with a no observed adverse effects limits
being set at 100 mg/kg in that toxicity trial (39).
Overall, this study is the first to show that CBDA and THCA
are readily absorbed and retained in dogs with some differences
observed in CBDA absorption and/or retention depending on
the medium used to deliver the oral treatment. The finding of
mid dosing concentrations of 75 ng/mL of CBD and CBDA or
greater suggests potential for therapeutic use when delivered at
1 mg/kg body weight for each of these cannabinoids with food.
A more interesting finding is the retention of THCA in the
serum of between 10 and 25 ng/mL. The exact functions of CBDA
and THCA physiologically suggest similar therapeutic benefits
to CBD that may have the potential to work synergistically
with CBD. These synergistic properties known as the “entourage
effect” are currently thought to be the primary reason that
lower CBD whole hemp extract dosing can be therapeutic when
compared to purified CBD (40,41). Although the hemp extract
product used in this study appears to be generally safe, the
results of this study cannot be translated to other products
due to differences in variable absorption dependent on carrier
oils, and cannabinoid and terpene profiles. This fact makes
recommendations of CBD-rich hemp products globally tenuous,
and veterinarians should become versed on products available
before using them clinically.
DATA AVAILABILITY STATEMENT
The raw data supporting the conclusions of this article will be
made available by the authors, without undue reservation.
ETHICS STATEMENT
The animal study was reviewed and approved by University of
Florida Institutional Animal Care and Use Committee.
AUTHOR CONTRIBUTIONS
JW, WS, and SC were responsible for conceptualization and
study design. All authors were involved in acquisition and
analysis of portions of the data, involved in manuscript
preparation/revisions, and approved this manuscript before
submission. The manuscript was drafted by JW.
ACKNOWLEDGMENTS
We would like to thank Ms. Amanda Howland and Mr. Reece
Prussin for their efforts in analysis and material preparation used
for this study.
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Frontiers in Veterinary Science | www.frontiersin.org 11 September 2020 | Volume 7 | Article 505
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Conflict of Interest: JW is currently a paid consultant for Ellevet Sciences, and
SC is currently an employee of Ellevet Sciences. The funding for this study was
provided to JW at the University of Florida by Ellevet Sciences. The funder was
involved in the study design under the guidance of author JW. The funder was not
involved in the collection, analysis, interpretation of data, the writing of this article,
or the decision to submit it for publication.
The remaining authors declare that the research was conducted in the absence of
any commercial or financial relationships that could be construed as a potential
conflict of interest.
Copyright © 2020 Wakshlag, Schwark, Deabold, Talsma, Cital, Lyubimov, Iqbal and
Zakharov. This is an open-access article distributed under the terms of the Creative
Commons Attribution License (CC BY). The use, distribution or reproduction in
other forums is permitted, provided the original author(s) and the copyright owner(s)
are credited and that the original publication in this journal is cited, in accordance
with accepted academic practice. No use, distribution or reproduction is permitted
which does not comply with these terms.
Frontiers in Veterinary Science | www.frontiersin.org 12 September 2020 | Volume 7 | Article 505
... Clinical trials in dogs and cats revealed an elimination halflife of 1.0-1.5 h when administered orally, although, in dogs Figure 1 summarizes the pharmacokinetics of the phytocannabinoids used in veterinary medicine (10,18,29). The pharmacokinetic parameters can be influenced by the products used as raw materials to prepare the extracts (8,31). For example, in a study by Deabold et al. (23), the pharmacokinetics of oral (soft chews for dogs and oil for cats) administration of CBD and CBDA obtained from hemp at a single dose of 2 mg/kg (based on CBD) every 12 h for 12 weeks was evaluated in healthy dogs and cats. ...
... Cats appear to have lower serum concentration and faster CBD elimination than dogs (33). Other clinical studies on the pharmacokinetic characteristics of CBD are summarized in Table 1 (23,30,31,(34)(35)(36)(37). ...
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The use of cannabinoids in both veterinary and human medicine is controversial for legal and ethical reasons. Nonetheless, the availability and therapeutic use of naturally occurring or synthetic phytocannabinoids, such as Δ ⁹ -tetrahydrocannabidiol and cannabidiol, have been the focus of attention in studies regarding their medical uses. This review aims to examine the role of cannabinoids in pain modulation by analyzing scientific findings regarding the signaling pathways of the endocannabinoid system and discussing the analgesic effects of synthetic cannabinoids compared to cannabinoid extracts and the extent and involvement of their receptors. In animals, studies have shown the analgesic properties of these substances and the role of the cannabinoid binding −1 (CB1) and cannabinoid binding −2 (CB2) receptors in the endocannabinoid system to modulate acute, chronic and neuropathic pain. This system consists of three main components: endogenous ligands (anandamide and 2-arachidonoylglycerol), G protein-coupled receptors and enzymes that degrade and recycle the ligands. Evidence suggests that their interaction with CB1 receptors inhibits signaling in pain pathways and causes psychoactive effects. On the other hand, CB2 receptors are associated with anti-inflammatory and analgesic reactions and effects on the immune system. Cannabis extracts and their synthetic derivatives are an effective therapeutic tool that contributes to compassionate pain care and participates in its multimodal management. However, the endocannabinoid system interacts with different endogenous ligands and neurotransmitters, thus offering other therapeutic possibilities in dogs and cats, such is the case of those patients who suffer from seizures or epilepsy, contact and atopic dermatitis, degenerative myelopathies, asthma, diabetes and glaucoma, among other inflammatory diseases. Moreover, these compounds have been shown to possess antineoplastic, appetite-stimulating, and antiemetic properties. Ultimately, the study of the endocannabinoid system, its ligands, receptors, mechanism of action, and signaling, has contributed to the development of research that shows that hemp-derived and their synthetic derivatives are an effective therapeutic alternative in the multimodal management of pain in dogs and cats due to their ability to prevent peripheral and central sensitization.
... 11 The pharmacokinetics of CBD, CBDA, THC, and tetrahydrocannabinolic acid for 3 oral forms (2 oil formulations and 1 soft chew) of CBD-rich hemp extract that contained near equal amounts of CBD and CBDA and minor amounts (,0.3% by weight) of THC and tetrahydrocannabinolic acid were measured in dogs. 12 The dogs were administered a dose of 2 mg/kg of CBD/CBDA (~1 mg/kg CBD and~1 mg/kg CBDA every 12 hours for 2 weeks). The pharmacokinetic values reported for these 3 forms were: C max , 124 6 62 to 226 6 89 ng/ mL; T max , 1.5 6 0.5 to 2.5 6 1.2 hours; t ½ , 3.8 6 0.3 to 4.4 6 1.4 hours; and AUC 0-24 , 635 6 399 to 826 6 74 hÁng/mL. ...
... The pharmacokinetic values reported for these 3 forms were: C max , 124 6 62 to 226 6 89 ng/ mL; T max , 1.5 6 0.5 to 2.5 6 1.2 hours; t ½ , 3.8 6 0.3 to 4.4 6 1.4 hours; and AUC 0-24 , 635 6 399 to 826 6 74 hÁng/mL. 12 In a study to treat Dravet syndrome (seizures) in children, oral doses of CBD oil at 5, 10, or 20 mg/ kg per day were administered. Plasma concentrations reached 200-400 ng/mL; however, because these subjects were clinical patients, they received other anticonvulsant medications that could have served as confounding factors. ...
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The purpose of this study was to determine the pharmacokinetics of cannabidiol (CBD), a potential treatment option that may alleviate pain in companion animals and humans, in the Hispaniolan Amazon parrot (Amazona ventralis). A pilot study administered a single oral dose of CBD in hemp oil at 10 mg/kg to 2 birds and 20 mg/kg to 2 birds. Because the maximum serum concentrations (Cmax) for these doses were 5.5 and 13 ng/mL, respectively, and the serum half-life was 2 hours for both groups, the doses were considered too low for clinical use in this species. Therefore, a study was designed in which 14 healthy 1214-year-old parrots of both sexes and weighing 0.240.35 kg (mean, 0.28 kg) were enrolled. Seven birds were administered 60 mg/kg CBD PO, and 7 birds were administered 120 mg/kg CBD PO. Blood samples were obtained at time 0, and at 0.5, 1, 2, 3, 4, 6, and 10 hours posttreatment in a balanced incomplete block design. Quantification of plasma CBD concentrations was determined by use of a validated liquid chromatographymass spectrometry assay. Pharmacokinetic parameters were determined by noncompartmental analysis. The areas under the curve (hng/mL) were 518 and 1863, Cmax (ng/ mL) were 213 and 562, and times to achieve Cmax (hours) were 0.5 and 4 for the 60 and 120 mg/kg doses, respectively. The serum half-life could not be determined in the 60 mg/kg treatment, but was 1.28 hours at 120 mg/kg. Adverse effects were not observed in any bird. The highly variable results and short half-life of the drug in Hispaniolan Amazon parrots, even at high doses, suggests that this drug formulation was inconsistent in achieving targeted concentrations as reported in other animal species.
... Treatments were divided evenly between the two daily concentrate meals, top-dressed and thoroughly mixed immediately prior to feeding. Levels of CBD supplementation were determined based on the previous literature in horses [15] and other species, using up to 1.5 mg CBD/kg BW [5,7,16,17] to avoid negative implications on liver health. An oil-based formulation was chosen due to ease of administration and higher bioavailability when compared to solid-based formulations [5,[18][19][20]. ...
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Thirty stock type geldings (15 ± 3 years; 556 ± 63 kg BW) were used in a randomized complete design over 28 days to determine the influence of cannabidiol (CBD) oil supplementation levels on body weight, body condition, and blood chemistry. Horses were randomly assigned to one of three dietary treatments (n = 10 per treatment) formulated with canola oil to provide 1.50 mg CBD/kg BW (TRTA), 0.75 mg CBD/kg BW (TRTB), or 0.00 mg CBD/kg BW (canola oil; CTRL). Treatments were top-dressed onto concentrate and individually administered twice daily. Horses were maintained in adjacent dry lots and received coastal bermudagrass hay ad libitum. Body weight and body condition scores (BCS) were obtained every 14 days. On day 0 and 28, blood was collected via jugular venipuncture and serum was harvested to perform a blood chemistry panel and drugs of abuse screening at the Texas Veterinary Medical Diagnostic Laboratory. Data were analyzed using PROC MIXED of SAS (v9.4), and the model included treatment, time, and the treatment × time interaction, and linear and quadratic orthogonal polynomial contrasts to partition sum of squares. Analysis of composited treatment samples revealed lower CBD concentrations than indicated from initial testing by the manufacturer (0.13 mg CBD/kg in TRTA; 0.12 mg CBD/kg in TRTB). At this level of supplementation, canola-based CBD oil was well-accepted by mature horses, banned substances were not detectable in blood, and blood chemistry parameters were not adversely affected as a result of supplementation. More research is warranted to describe the discrepancy between formulated levels compared to tested levels of CBD in the canola-based supplement.
... Recently, the use of intravenous lipid therapy has been described for the treatment of cases of marijuana intoxication in dogs, the prognosis is good with complete recovery in the vast majority of cases 31. [22][23][24][25][26][27][28][29] ...
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Studies with Cannabidiol (CBD) to reduce pain in animals have increased exponentially in recent years due to the great interest generated by the use of natural and homeopathic medicine to manage different pathologies. However, for dogs handling, the information is still limited. We’ve found that veterinary ethnobotanical studies carried out in Mexico City at the Faculty of Veterinary Medicine of the UNAM on the analgesic effect of CBD in animals are few and these studies are mostly carried out for use in larger animals (goats, bovines...) On the homeopathic medicine side, there is Dr. Monica Fehlmann from Switzerland, who has a homeopathy program for animals, reiki treatments, healing massages, bioresonance or acupuncture for the physical and spiritual health of pets, while the university corporation of Santa Rosa de Cabal (located in Risaralda, Colombia), ventured to carry out experimental studies with 16 dogs, using (tetrahydrocannabinol) THC as part of their treatments, she based her research on current studies that support the analgesic and antiepileptic effects of THC in critical canine conditions. Various pathologies have been studied to reduce pain, however, the ones with more supporting background are osteoarthritis, inflammation, epilepsy, seizures, behavioral problems, anxiety, neurodegenerative diseases and dermatological problems. Seizures are the most studied application of CBD in people, and it's starting to be the most studied one in dogs. Multiple investigations have shown that CBD is capable of reducing the intensity and frequency of seizures in dogs that were diagnosed with idiopathic epilepsy
... In recent years, new clinical studies aimed to elucidate the role of CBD in the treatment of various diseases in dogs, such as osteoarthritis (17 -21), seizures (22, 23), atopic dermatitis (24) and anxiety (25). In addition, recent studies investigated the safety and side effects of various cannabinoid dosages and formulations for dogs (1,(26)(27)(28)(29)(30) and cats (1,26,31). Two of the most studied canine diseases, treated with CBD-basd products, are osteoarthritis (17 -21), and epilepsy (22, 23). ...
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The aim of the present study was to obtain information about the experiences of Slovenian pet owners on the use of cannabidiol (CBD) products in their pets. An open online survey targeted Slovenian owners of cats and dogs who have used CBD to treat their pets. Questions pertained to demographic data, animal data, health status of the animals, CBD formulations and experiences with use. Descriptive statistics and frequency distributions were performed using the survey software. A total of 41 respondents participated in the survey, most of whom were female (87.8 %) and between 31 and 50 years old (56.1 %). Most respondents (90.2 %) were dog owners. Cannabidiol (CBD)-based products were mainly used to treat orthopaedic and oncologic conditions, as adjunctive therapy to other medications. Oil formulations were used by most dog (85.2 %) and all cat owners. Participants predominantly reported positive effects, such as improved well-being, increased activity, and reduced pain. The results suggest that Slovenian pet owners who used CBD-based products as a treatment for their pets were overall satisfied with the effects of these products. However, there were still reports of some adverse effects, such as drowsiness, increased appetite, and thirst. Further research is essential to improve practices related to cannabis-based medicines for pets, especially CBD, and to put an end to the trial- and error- based therapeutic approach of pet owners and veterinarians. Long-term, large-scale research studies are needed to clarify the role of CBD as a treatment option for osteoarthritis, chronic pain, cancer, behavioral problems, and other chronic inflammatory conditions in dogs and cats.
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Introduction In the last few years, different formulations containing cannabidiol (CBD) were tested with regard to its efficacy on chronic pain, refractory epilepsy, anxiety, aggressive behavior and atopic dermatitis in dogs. CBD is generally administered orally, but its low bioavailability, probably due to a first-pass metabolism, represents a great limitation. The aim of this study was to evaluate if CBD bioavailability increases after oral transmucosal administration (OTM) compared to oral treatment. Methods Twelve dogs diagnosed with mild chronic pain were enrolled in the study and treated once orally or OTM (6 dogs/group) with a pure CBD in oil formulation at a dosing rate of 1 mg/kg b.w. At prefixed time points, blood samples were collected to define CBD plasma concentrations vs. time profiles, and the main pharmacokinetics parameters were obtained by non-compartmental model. Results CBD Cmax, Tmax, terminal half-life and AUC 0 − t were 206.77 ± 167 and 200.33 ± 158.33 ng/mL, 2.17 ± 0.98 and 1.92 ± 1.11 h, 2.67 ± 0.53 and 2.62 ± 0.64 h, 647.51 ± 453.17, and 536.05 ± 370.21 h * ng/mL, following oral and OTM administration, respectively. No significant difference in pharmacokinetic parameters were observed between treatments. Discussion The OTM administration did not increase cannabidiol bioavailability compared to oral treatment. The almost perfectly superimposable mean plasma concentrations of cannabidiol following the two treatments suggests that CBD is not able to be adsorbed by the oral mucosa or that its absorption is very scarce, and that CBD is swallowed and absorbed in the gastrointestinal tract.
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Cannabidiol (CBD) containing dog food and treats are widely commercially available, mirroring the growing popularity of CBD as a supplement for humans. Despite this, experimental evidence of the safety and efficacy of long-term oral exposure in dogs is lacking. The purpose of this study was to address the gap in knowledge around the longer-term suitability and tolerance of a broad-spectrum CBD (THC-free) distillate in clinically healthy dogs. The study was a randomized, placebo-controlled, and blinded study where one group of twenty dogs received daily CBD capsules at a dose of 4 mg/kg of body weight (BW) for a period of 6 months. The control group of twenty dogs received placebo capsules. A comprehensive suite of physiological health measures was performed throughout the study at baseline, and after 2, 4, 10, 18, and 26 weeks of exposure, followed by 4 weeks of washout. CBD concentrations were measured at the same cadence in plasma, feces and urine. Health measures included biochemistry, hematology, urinalysis, in addition to fortnightly veterinary examinations, twice daily well-being observations, and a daily quality-of-life survey. Biochemistry and hematology showed no clinically significant alterations apart from a transient elevation in alkaline phosphatase (ALP) in just over half of the dogs receiving CBD. This elevation was observed in the absence of concurrent elevations of other liver parameters, and without any adverse effects on health and wellbeing. Furthermore, bone alkaline phosphatase (BALP) was simultaneously elevated with a significant, strong ( r > 0.9) positive correlation between the two measures, suggesting that the elevation of total ALP was at least partly due to the bone-derived isoform. This study provides evidence that a once-daily oral dose of 4 mg CBD/kg BW is well tolerated in clinically healthy dogs for a duration of 6-months.
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The objective of this 90-day pilot clinical trial was to assess the impact of a full-spectrum product containing hemp extract and hemp seed oil on dogs with chronic mal-adaptive pain. A total of 37 dogs diagnosed with chronic maladaptive pain primarily as a result of osteoarthritis were enrolled in the study. The dogs were given an initial physical examination that included systematic pain palpa- tion, mapping of pain patterns, informal gait analysis, metabolic profile, and owner interview. The same palpa-tions and mappings were performed during each biweekly assessment to identify trends, chart progress, and inform dose adjustments. The metabolic parameters were repeated at the end of the study. Of the 32 dogs that completed the study, 30 dogs demonstrated improved pain support. Of the 23 dogs in the study that were taking gabapentin at the time of enrollment, 10 dogs were able to discontinue the gabapentin, and an additional 11 dogs were able to have their daily dose reduced with the addition of the cannabi-diol (CBD) oil. Conclusion: The addition of a hemp-derived CBD oil appears to positively affect dogs with chronic maladaptive pain by decreasing their pain, thereby improving their mobility and quality of life. The reduction in gabapentin dose may be the result of changes in analgesia and/or sedation with the addition of the hemp oil extract.
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Due to the myriad of laws concerning cannabis, there is little empirical research regarding the veterinary use of cannabidiol (CBD). This study used the Veterinary Information Network (VIN) to gauge US veterinarians' knowledge level, views and experiences related to the use of cannabinoids in the medical treatment of dogs. Participants (n = 2130) completed an anonymous, online survey. Results were analyzed based on legal status of recreational marijuana in the participants' state of practice, and year of graduation from veterinary school. Participants felt comfortable in their knowledge of the differences between Δ9-tetrahydrocannabinol (THC) and marijuana, as well as the toxic effects of marijuana in dogs. Most veterinarians (61.5%) felt comfortable discussing the use of CBD with their colleagues, but only 45.5% felt comfortable discussing this topic with clients. No differences were found based on state of practice, but recent graduates were less comfortable discussing the topic. Veterinarians and clients in states with legalized recreational marijuana were more likely to talk about the use of CBD products to treat canine ailments than those in other states. Overall, CBD was most frequently discussed as a potential treatment for pain management, anxiety and seizures. Veterinarians practicing in states with legalized recreational marijuana were more likely to advise their clients and recommend the use of CBD, while there was no difference in the likelihood of prescribing CBD products. Recent veterinary graduates were less likely to recommend or prescribe CBD. The most commonly used CBD formulations were oil/extract and edibles. These were most helpful in providing analgesia for chronic and acute pain, relieving anxiety and decreasing seizure frequency/severity. The most commonly reported side-effect was sedation. Participants felt their state veterinary associations and veterinary boards did not provide sufficient guidance for them to practice within applicable laws. Recent graduates and those practicing in states with legalized recreational marijuana were more likely to agree that research regarding the use of CBD in dogs is needed. These same groups also felt that marijuana and CBD should not remain classified as Schedule I drugs. Most participants agreed that both marijuana and CBD products offer benefits for humans and expressed support for use of CBD products for animals.
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Cannabidiol (CBD) is a non-psychotropic phytocannabinoid which represents one of the constituents of the “phytocomplex” of Cannabis sativa. This natural compound is attracting growing interest since when CBD-based remedies and commercial products were marketed. This review aims at exhaustively addressing the extractive and analytical approaches that have been developed for the isolation and quantification of CBD. Recent updates on cutting-edge technologies were critically examined in terms of yield, sensitivity, flexibility and performances in general, and are reviewed alongside original representative results. As an add-on to currently available contributions in the literature, the evolution of novel, efficient synthetic approaches for the preparation of CBD, a procedure which is appealing for the pharmaceutical industry, is also discussed. Moreover, given the increasing interest on the therapeutic potential of CBD and the limited understanding of the undergoing biochemical pathways, the reader will be updated about recent in silico studies on the molecular interactions of CBD towards several different targets attempting to fill this gap. Computational data retrieved from the literature have been integrated with novel in silico experiments, critically discussed to provide a comprehensive and updated overview on the undebatable potential of CBD and its therapeutic profile.
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Introduction: Sativex® spray is clinically utilized to deliver delta9-tetrahydrocannabinol and cannabidiol to oral mucosa for systemic absorption. We challenge the consensus that the mechanism of absorption following the oro-mucosal application occurs via the buccal tissue. Areas covered: Correctness of the consensus of this absorption pathway arose when reviewing publications regarding the influence fed versus fasting states have on pharmacokinetics of these cannabinoids administered to oral mucosa. This finding is more suitable for per oral administration, where stomach content affects the absorption profile. We hypothesize that these cannabinoids are ingested and absorbed in the gastro-intestinal tract. Expert opinion: Although clinical importance of Sativex® is not disputed, the wide acceptance of its being a successful example of drug delivery through oral mucosa is questionable. Sativex® acts as example for other drugs delivered to oral mucosa for systemic absorption and unintentionally washed by the saliva flow into the gastro-intestinal tract. Delivery of each medicine through oral mucosa should be validated in-vivo to ensure this route to be the predominant one. Revealing the underlying absorption mechanisms would enable predicting the impact of different physiological parameters such as saliva flow and fed/fasting states on the pharmacokinetics of the delivered medication.
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Objective: To evaluate the pharmacokinetics of a purified oral cannabidiol (CBD) capsule administered with and without food in adults with refractory epilepsy. Methods: Adult patients who were prescribed CBD for seizures, had localization-related intractable epilepsy with ≥4 seizures per month, and qualified for Minnesota cannabis were enrolled. A single dose of 99% pure CBD capsules was taken under both fasting (no breakfast) and fed (high fat 840-860 calorie) conditions. Blood sampling for CBD plasma concentrations was performed under each condition between 0 and 72 hours post-dose and measured by a validated liquid chormatography-mass spectometry assay. CBD pharmacokinetic profiles including maximum concentration (Cmax ), area-under-the-curve from zero to infinity (AUC0-∞ ), and time-to-maximum concentration (Tmax ) were calculated. The confidence intervals (CIs) for log-transformed Cmax and AUC0-∞ ratios between fed and fasting states were calculated. Seizure and adverse events information was collected. Results: Eight patients completed the study. On average Cmax was 14 times and AUC0-∞ 4 times higher in the fed state. The 90% CI for the ratio of fed versus fast conditions for Cmax and AUC0-∞ were 7.47-31.86 and 3.42-7.82, respectively. No sequence or period effect for Cmax and AUC0-∞ was observed. No adverse events were reported. Significance: Administering CBD as a capsule rather than a liquid allows for more precise determination of pharmacokinetics parameters and is more representative of CBD swallowed products. The fat content of a meal can lead to significant increases in Cmax and AUC0-∞ and can account for variability in bioavailability and overall drug exposure within patients with oral products.
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Objective: To assess the effect of oral cannabidiol (CBD) administration in addition to conventional antiepileptic treatment on seizure frequency in dogs with idiopathic epilepsy. Design: Randomized blinded controlled clinical trial. Animals: 26 client-owned dogs with intractable idiopathic epilepsy. Procedures: Dogs were randomly assigned to a CBD (n = 12) or placebo (14) group. The CBD group received CBD-infused oil (2.5 mg/kg [1.1 mg/lb], PO) twice daily for 12 weeks in addition to existing antiepileptic treatments, and the placebo group received noninfused oil under the same conditions. Seizure activity, adverse effects, and plasma CBD concentrations were compared between groups. Results: 2 dogs in the CBD group developed ataxia and were withdrawn from the study. After other exclusions, 9 dogs in the CBD group and 7 in the placebo group were included in the analysis. Dogs in the CBD group had a significant (median change, 33%) reduction in seizure frequency, compared with the placebo group. However, the proportion of dogs considered responders to treatment (≥ 50% decrease in seizure activity) was similar between groups. Plasma CBD concentrations were correlated with reduction in seizure frequency. Dogs in the CBD group had a significant increase in serum alkaline phosphatase activity. No adverse behavioral effects were reported by owners. Conclusions and clinical relevance: Although a significant reduction in seizure frequency was achieved for dogs in the CBD group, the proportion of responders was similar between groups. Given the correlation between plasma CBD concentration and seizure frequency, additional research is warranted to determine whether a higher dosage of CBD would be effective in reducing seizure activity by ≥ 50%.
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Cannabidiol (CBD) is a highly touted product for many different disorders among the lay press. Numerous CBD products are available, ranging from a US Food and Drug Administration (FDA)‐approved product called Epidiolex to products created for medical marijuana dispensaries and products sold in smoke shops, convenience stores, and over the Internet. The legal status of the non–FDA‐approved products differs depending on the source of the CBD and the state, while the consistency and quality of the non–FDA‐approved products vary markedly. Without independent laboratory verification, it is impossible to know whether the labeled CBD dosage in non–FDA‐approved CBD products is correct, that the delta‐9‐tetrahydrocannabinol content is <0.3%, and that it is free of adulteration and contamination. On the Internet, CBD has been touted for many ailments for which it has not been studied, and in those diseases with evaluable human data, it generally has weak or very weak evidence. The control of refractory seizures is a clear exception, with strong evidence of CBD's benefit. Acute CBD dosing before anxiety‐provoking events like public speaking and the chronic use of CBD in schizophrenia are promising but not proven. CBD is not risk free, with adverse events (primarily somnolence and gastrointestinal in nature) and drug interactions. CBD has been shown to increase liver function tests and needs further study to assess its impact on suicidal ideation.