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ORIGINAL RESEARCH
published: 23 July 2018
doi: 10.3389/fvets.2018.00165
Frontiers in Veterinary Science | www.frontiersin.org 1July 2018 | Volume 5 | Article 165
Edited by:
Troy N. Trumble,
University of Minnesota Twin Cities,
United States
Reviewed by:
Gareth Edward Zeiler,
University of Pretoria, South Africa
Joao Henrique Neves Soares,
Virginia Tech, United States
*Correspondence:
Joseph J. Wakshlag
jw37@cornell.edu
Specialty section:
This article was submitted to
Veterinary Surgery and
Anesthesiology,
a section of the journal
Frontiers in Veterinary Science
Received: 25 February 2018
Accepted: 02 July 2018
Published: 23 July 2018
Citation:
Gamble L-J, Boesch JM, Frye CW,
Schwark WS, Mann S, Wolfe L,
Brown H, Berthelsen ES and
Wakshlag JJ (2018)
Pharmacokinetics, Safety, and Clinical
Efficacy of Cannabidiol Treatment in
Osteoarthritic Dogs.
Front. Vet. Sci. 5:165.
doi: 10.3389/fvets.2018.00165
Pharmacokinetics, Safety, and
Clinical Efficacy of Cannabidiol
Treatment in Osteoarthritic Dogs
Lauri-Jo Gamble 1, Jordyn M. Boesch 1, Christopher W. Fr ye 1, Wayne S. Schwark2,
Sabine Mann 3, Lisa Wolfe 4, Holly Brown 5, Erin S. Berthelsen 1and Joseph J. Wakshlag 1
*
1Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States, 2Department
of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States, 3Department of
Population Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY, United States, 4Proteomic and
Metabolomic Facility, Colorado State University, Fort Collins, CO, United States, 5Metzger Animal Hospital, State College,
PA, United States
Objectives: The objectives of this study were to determine basic oral pharmacokinetics,
and assess safety and analgesic efficacy of a cannabidiol (CBD) based oil in dogs with
osteoarthritis (OA).
Methods: Single-dose pharmacokinetics was performed using two different doses
of CBD enriched (2 and 8 mg/kg) oil. Thereafter, a randomized placebo-controlled,
veterinarian, and owner blinded, cross-over study was conducted. Dogs received each
of two treatments: CBD oil (2 mg/kg) or placebo oil every 12 h. Each treatment lasted
for 4 weeks with a 2-week washout period. Baseline veterinary assessment and owner
questionnaires were completed before initiating each treatment and at weeks 2 and 4.
Hematology, serum chemistry and physical examinations were performed at each visit.
A mixed model analysis, analyzing the change from enrollment baseline for all other time
points was utilized for all variables of interest, with a p≤0.05 defined as significant.
Results: Pharmacokinetics revealed an elimination half-life of 4.2 h at both doses and no
observable side effects. Clinically, canine brief pain inventory and Hudson activity scores
showed a significant decrease in pain and increase in activity (p<0.01) with CBD oil.
Veterinary assessment showed decreased pain during CBD treatment (p<0.02). No
side effects were reported by owners, however, serum chemistry showed an increase in
alkaline phosphatase during CBD treatment (p<0.01).
Clinical significance: This pharmacokinetic and clinical study suggests that 2 mg/kg
of CBD twice daily can help increase comfort and activity in dogs with OA.
Keywords: cannabidiol, CBD oil, hemp, canine, osteoarthritis, pharmacokinetic
INTRODUCTION
Routine nonsteroidal anti-inflammatory drug (NSAID) treatments, though efficacious, may not
provide adequate relief of pain due to osteoarthritis (OA) and might have potential side effects
that preclude its use, particularly in geriatric patients with certain comorbidities, such as kidney
or gastrointestinal pathologies (1–4). In a systematic review of 35 canine models of OA and
29 clinical trials in dogs, treatment with NSAIDs caused adverse effects in 35 of the 64 (55%)
Gamble et al. Cannabidiol and Osteoarthritis in Dogs
studies, most commonly being gastro-intestinal signs (3).
Although other pharmacological agents are advocated, such as
gabapentin or amantadine, there is little evidence regarding their
efficacy in dogs with chronic or neuropathic pain related to OA.
Recent medical interest in alternative therapies and modalities for
pain relief has led many pet owners to seek hemp related products
rich in cannabinoids.
The endocannabinoid receptor system is known to play a
role in pain modulation and attenuation of inflammation (5–
7). Cannabinoid receptors (CB1 and CB2) are widely distributed
throughout the central and peripheral nervous system (8–10) and
are also present in the synovium (11). However, the psychotropic
effects of certain cannabinoids prevent extensive research into
their use as single agents for pain relief (5,12). The cannabinoids
are a group of as many as 60 different compounds that may
or may not act at CB receptors. One class of cannabinoids,
cannabidiol (CBD), may actually be an allosteric non-competitive
antagonist of CB receptors (13). In lower vertebrates, CBD is also
reported to have immunomodulatory (14), anti-hyperalgesic (15,
16), antinociceptive (17,18), and anti-inflammatory actions (5,
19), making it an attractive therapeutic option in dogs with OA.
Currently there are several companies distributing nutraceutical
derivatives of industrial hemp, rich in cannabinoids for pets, yet
little scientific evidence regarding safe and effective oral dosing
exists.
The objectives of this study were to determine: (1) single-
dose oral pharmacokinetics, (2) short-term safety, and (3)
efficacy of this novel CBD-rich extract, as compared to
placebo, in alleviating pain in dogs with OA. Our underlying
hypotheses were that appropriate dosing of CBD-rich oil would
safely diminish perceived pain and increase activity in dogs
with OA.
MATERIALS AND METHODS
CBD Oil and Protocols Approval
The industrial hemp used in this study was a proprietary
hemp strain utilizing ethanol and heat extraction with the final
desiccated product reconstituted into an olive oil base containing
∼10 mg/mL of CBD as an equal mix of CBD and carboxylic
acid of CBD (CBDa), 0.24 mg/mL tetrahydrocannabinol
(THC), 0.27 mg/mL cannabichromene (CBC), and 0.11 mg/mL
cannabigerol (CBG); all other cannabinoids were less than
0.01 mg/mL. Analysis of five different production runs using
a commercial analytical laboratory (MCR Laboratories,
Framingham, MA) show less than a 9% difference across batches
for each of the detected cannabinoids listed above. The study was
performed after the Cornell University institutional animal care
and use committee (IACUC) approved the study following the
guidelines for animal use according to the IACUC. Client owned
dogs were enrolled after informed consent in accordance with
the Declaration of Helsinki.
Abbreviations: CBD, cannabidiol; CB, cannabinoid; CBDa, carboxylic acid of
CBD; THC, tetrahydrocannabinol; CBC, cannabichromene; CBG, cannabigerol;
CBPI, Canine Brief Pain Inventory.
Pharmacokinetics
An initial investigation into single-dose oral pharmacokinetics
was performed with 4 beagles (3.5–7 years, male castrated, 10.7–
11.9 kg). Each dog received a 2 mg/kg and an 8 mg/kg oral
dosage of CBD oil, with a 2-week washout period between
each experiment. The dogs were fed 2 h after dosing. Physical
examination was performed at 0, 4, 8, and 24 h after dosing.
Attitude, behavior, proprioception, and gait were subjectively
evaluated at each time point during free running/walking
and navigation around standard traffic cones (weaving). Five
milliliters of blood was collected at time 0, 0.5, 1, 2, 4, 8, 12,
and 24 h after oil administration. Blood samples were obtained
via jugular venipuncture and transferred to a coagulation tube
for 20 min. Samples were centrifuged with a clinical centrifuge at
3,600 ×g for 10 min; serum was removed and stored at −80◦C
until analysis using liquid chromatography-mass spectrometry
(LC-MS) at Colorado State University Core Mass Spectrometry
facility.
Extraction of CBD From Canine Serum and
Mass Spectrometry Analysis
CBD was extracted from canine serum using a combination of
protein precipitation and liquid-liquid extraction using n-hexane
as previously described (20), with minor modifications for
microflow ultra-high pressure liquid chromatography (UHPLC).
Briefly, 0.05 mL of canine serum was subjected to protein
precipitation in the presence of ice-cold acetonitrile (80% final
concentration), spiked with deuterated CBD as the internal
standard (0.06 mg/mL, CDB-d3 Cerilliant, Round Rock, T X,
USA). 0.2 mL of water was added to each sample prior to the
addition of 1.0 mL of hexane to enhance liquid-liquid phase
separation. Hexane extract was removed and concentrated to
dryness under laboratory nitrogen. Prior to LC-MS analysis,
samples were resuspended in 0.06 mL of 100% acetonitrile.
A standard curve using the CBD analytical standard was
prepared in canine serum non-exposed to CBD and extracted
as above. Cannabidiol concentration in serum was quantified
using a chromatographically coupled triple-quadropole mass
spectrometer (UHPLC-QQQ-MS) using similar methods as
previously described (21).
CDB Serum Concentration Data Analysis
From the UHPLC-QQQ-MS data, peak areas were extracted for
CBD detected in biological samples and normalized to the peak
area of the internal standard CBD-d3, in each sample using
Skyline (22) as well as an in-house R Script (www.r-project.org).
CBD concentrations were calculated to nanograms per mL of
serum as determined by the line of regression of the standard
curve (r2=0.9994, 0–1,000 ng/mL). For this assay, the limits of
detection (LOD) and limits of quantification (LOQ) represent the
lower limits of detection and quantification for each compound
in the matrix of this study (23,24). Pharmacokinetic variables
were estimated by means of non-compartmental analysis,
utilizing a pharmacokinetic software package (PK Solution,
version 2.0, Montrose, CO, USA).
Frontiers in Veterinary Science | www.frontiersin.org 2July 2018 | Volume 5 | Article 165
Gamble et al. Cannabidiol and Osteoarthritis in Dogs
Inclusion and Exclusion Criteria for the
Clinical Trial
The study population consisted of client-owned dogs presenting
to Cornell University Hospital for Animals for evaluation and
treatment of a lameness due to OA. Dogs were considered for
inclusion in the study if they had radiographic evidence of
OA, signs of pain according to assessment by their owners,
detectable lameness on visual gait assessment and painful
joint(s) on palpation. Each dog had an initial complete blood
count ([CBC] Bayer Advia 120, Siemens Corp., New York,
NY, USA) and serum chemistry analysis (Hitachi 911, Roche
Diagnostics, Indianapolis, IN, USA) performed to rule out any
underlying disease that might preclude enrolment. Elevations
in alkaline phosphatase (ALP), alanine aminotransferase (ALT),
and aspartate aminotransferase (AST) were allowed if prior
hepatic ultrasound was deemed within normal limits except
for potential non-progressive nodules (possible hepatic nodular
hyperplasia). All owners completed a brief questionnaire to
define the affected limb(s), duration of lameness, and duration
of analgesic or other medications taken. All dogs underwent
radiographic examination of affected joints and a radiologist
confirmed the presence or absence of OA, and excluded the
presence of concomitant disease that might preclude them from
enrolment (i.e., lytic lesions).
During the trial, dogs were only allowed to receive NSAIDs,
fish oil, and/or glucosamine/chondroitin sulfate without any
change in these medications for 4 weeks prior to or during
the 10-week study period as standard of care for the disease
process. Other analgesic medications used, such as gabapentin
and tramadol, were discontinued at least 2 weeks prior to
enrolment. Dogs were excluded if they had evidence of renal,
uncontrolled endocrine, neurologic, or neoplastic disease, or
were undergoing physical therapy. Every dog was fed its regular
diet with no change allowed during the trial.
Clinical Trial
The study was a randomized, placebo-controlled, owner and
veterinarian double-blind, cross-over trial. Dogs received each
of two treatments in random order (Randomizer iPhone
Application): CBD, 2 mg/kg every 12 h, or placebo (an equivalent
volume of olive oil with 10 parts per thousands of anise oil and 5
parts per thousands of peppermint oil to provide a similar herbal
smell) every 12 h. Each treatment was administered for 4 weeks
with a 2-week washout period in between treatments. Blood was
collected to repeat complete blood counts and chemistry analysis
at weeks 2 and 4 for each treatment.
At each visit, each dog was evaluated by a veterinarian based
on a scoring system previously reported (25) as well as by its
owner (canine brief pain inventory [CBPI], Hudson activity
scale) before treatment initiation and at weeks 2 and 4 thereafter
(26–28).
Statistical Analysis
Initial power analysis was performed to assess number of
dogs needed for this study as a cross over design with
a power set 0.80 and alpha of 0.05 using prior data
suggesting a baseline CBPI or Hudson score change of
∼15 points (two tailed) with a standard deviation of
20. When calculated it was assumed that 14 dogs would
be necessary to find differences in outcomes of interest
(29).
Statistical analysis was performed with a commercially
available software package (JMP 12.0, Cary, NC, USA). All
continuous data were assessed utilizing a Shapiro–Wilk test for
normality. Considering a majority of our blood, serum and
scoring data were normally distributed a mixed model analysis
was used to analyze these outcomes, including the fixed effects
of treatment, time, sequence of treatment assignment, gender,
age, NSAID usage, treatment ×time; as well as random effects
of observation period, period nested within dog, time point
nested within period nested within dog to account for the
hierarchical nature of data in a cross-over design as well as
repeated measurements for each dog. For ordinal veterinary
scoring data a similar linear mixed model was used, but
differences from baseline were first calculated to approximate
a normal distribution to meet assumptions for a mixed model
analysis. Residual diagnostics of all final models showed that
residuals were normally distributed and fulfilled the assumption
of homoscedasticity, and assumptions where therefore met. This
statistical modeling approach allowed for adequate control of
hierarchical data structure necessary in a cross-over design,
as well as for the performance of easily interpretable time
×treatment Tukey post-hoc comparisons that were our main
interest, as compared to an ordinal logistical regression (30,
31). To control for baseline differences and therefore the
possible difference in relative change in CBPI pain, and activity
interference assessments and Hudson scoring across dogs, the
initial CPBI or Hudson Scores were included for these analyses
as a covariate. Pairwise comparisons between all-time points
of both groups were corrected for multiple comparisons with
Tukey’s post-hoc tests to examine the interaction of time and
treatment variables, and to assess differences between change
from baseline at any time point as they related to treatment.
Ap-value of less than 0.05 was defined as the significance
cut-off.
RESULTS
Pharmacokinetics
Pharmacokinetics demonstrated that CBD half-life of
elimination median was 4.2 h (3.8–6.8 h) for the 2 mg/kg dose,
and 4.2 h (3.8–4.8 h) for the 8 mg/kg dose (Table 1). Median
maximal concentration of CBD oil was 102.3 ng/mL (60.7–
132.0 ng/mL; 180 nM) and 590.8 ng/mL (389.5–904.5 ng/mL;
1.2 uM) and was reached after 1.5 and 2 h, respectively, for 2
and 8 mg/kg doses. No obvious psychoactive properties were
observed on evaluation at any time point during the 2 and
8 mg/kg doses over 24 h. These results led to dosing during the
clinical trial at 2 mg/kg body weight every 12 h, due the cost
prohibitive nature of 8 mg/kg dosing for most larger patients, the
impractical nature of more frequent dosing, the volume of oil
necessary and anecdotal reports surrounding 0.5-2 mg/kg dosing
recommended by other vendors.
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Gamble et al. Cannabidiol and Osteoarthritis in Dogs
TABLE 1 | Serum pharmacokinetic of single oral dosing (2 mg and 8mg/kg) of CBD oil in dogs.
Cmax (ng/mL) Tmax (h) T1/2 elim (h) AUC 0-t (ng-hr/mL) MRT (h)
DOSE (2 mg/kg)
Dog 1 61 1 4.4 183 6.0
Dog 2 132 1 3.9 351 4.2
Dog 3 102 2 3.8 382 5.1
Dog 4 101 2 6.8 437 9.1
Median (Range) 102 (61–132.0) 1.5 (1.0–2.0) 4.2 (3.8–6.8) 367 (183–437) 5.6 (4.2–9.1)
DOSE (8 mg/kg)
Dog 1 499 2 3.8 2,928 5.7
Dog 2 389 1 4.8 1,753 7.0
Dog 3 905 2 4.2 3,048 5.1
Dog 4 682 2 4.1 2,389 5.2
Median (Range) 591 (389–905) 2.0 (1.0–2.0) 4.2 (3.8–4.8) 2,658 (1,753–3,048) 5.6 (5.1–7.0)
Cmax, maximum concentration; Tmax, time of maximum concentration; T1/2 el, half-life of elimination; AUC 0-t, area under the curve (time 0–24 h); MRT, median residence time.
Dogs Included in the Clinical Trial
Twenty-two client-owned dogs with clinically and
radiographically confirmed evidence of osteoarthritis were
recruited. Sixteen of these dogs completed the trial and were
included in the analyses; their breed, weight, age, sex, worse
affected limb, radiographic findings, use of NSAIDs and
sequence of treatments are summarized in Table 2. Dogs
were removed due to osteosarcoma at the time of enrolment,
gastric torsion (placebo oil), prior aggression issues (CBD
oil), pyelonephritis/kidney insufficiency (CBD oil), recurrent
pododermatitis (placebo oil), and diarrhea (placebo oil).
Clinical Trial
CBPI and Hudson change from baseline scores showed a
significant decrease in pain and increase in activity (p<0.01)
at week 2 and 4 during CBD treatment when compared to
baseline week 0, while no other statistical significances were
observed across treatment in this cross-over design (Table 3).
Lameness as assessed by veterinarians showed an increase from
baseline in lameness with age (p<0.01), whereas NSAID use
(p=0.03) reduced lameness scores. Veterinary pain scores
showed a decrease from baseline in dogs on NSAIDs (p<0.01).
CBD oil resulted in a decrease in pain scores when compared to
baseline on evaluation at both week 2 and week 4 (p<0.01 and
p=0.02, respectively), and week 2 CBD oil treatment was lower
than baseline placebo treatment (p=0.02) and week 4 placebo
treatment (p=0.02). No other veterinary pain comparisons were
statistically significant. No changes were observed in weight-
bearing capacity when evaluated utilizing the veterinary lameness
and pain scoring system (Table 3).
Chemistry analysis and CBC were performed at each visit.
No significant change in the measured CBC values was noted
in either the CBD oil or placebo treated dogs (data not shown).
Serum chemistry values were not different between placebo
compared to CBD oil (Table 4), except for alkaline phosphatase
(ALP) which significantly increased over time from baseline
by week 4 of CBD oil treatment (p<0.01); with nine of
the 16 dogs showing increases over time (Figure 1). Glucose
was increased in dogs receiving the placebo oil at each time
point (p=0.04) and creatinine levels increased over time in
both dogs receiving CBD oil and those receiving placebo oil
(p<0.01); though all values remained within reference ranges.
Other notable significances in serum chemistry values were
associated with primarily age or NSAID use. An increase in
age was associated with significantly higher blood urea nitrogen
(BUN; p<0.01), calcium (p=0.01), phosphorus (p<0.01),
alanine aminotransferase (ALT; p=0.03), alkaline phosphatase
(ALP; p=0.01), gamma glutamyltransferase (GGT; p=0.02),
globulin (p=0.02), and cholesterol (p<0.01) values. NSAID use
was associated with significantly higher BUN (p=0.003), and
creatinine (p=0.017), and significant decreases in total protein
(p<0.001) and serum globulin (p<0.001).
DISCUSSION
To date, an objective evaluation of the pharmacokinetics of a
commercially available industrial hemp product after oral dosing
in dogs is absent. This study showed that the terminal half-
life of oral CBD, as the most abundant cannabinoid in this
specific preparation when in an oil base, was between 4 and 5 h,
suggesting it was bioavailable with a dosing schedule of 2 mg/kg
at least twice daily. This half-life was shorter than a previous
report after intravenous (1.88–2.81 and 3.75–5.63 mg/kg) and
oral (7.5–11.25 mg/kg) administration (32). In the intravenous
study, CBD distribution was rapid, followed by prolonged
elimination with a terminal half-life of 9 h. When examining
prior oral CBD bioavailability it was determined to be low and
highly variable (0–19% of dose) with three dogs showing no
absorption. This may be due to the first pass effect in the liver,
and the product was not in an oil base, but a powder within
a gelatin capsule being a different delivery vehicle (32). After
initially seeing no neurological effects at the 2 mg/kg dose a
8 mg/kg dose was chosen to assess the potential neurological
effects since mistaken overdosing can occur clinically, and a
higher dose might have been necessary since the prior study
showed poor absorption. Although our dogs were fasted the
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Gamble et al. Cannabidiol and Osteoarthritis in Dogs
TABLE 2 | Characteristics of dogs enrolled in a placebo-controlled study investigating the effects of CBD on osteoarthritis.
Breed Weight (kg) Age (years) Sex Radiographic findings and OA localization NSAID
Rottweiler 35.3 10 FS - Moderate, intracapsular swelling with moderate osteophytosis, left stifle Carprofen
(2.1 mg/kg BID)
Mix 30.6 13 MC - Moderate-to-severe, right-shoulder osteoarthrosis; mild, left-shoulder
osteoarthrosis
- Moderate-to-severe, bilateral hip osteoarthrosis
None
Mix 27.2 9 FS - Moderate medial coronoid remodeling
(with fragmentation on the right) and bilateral elbow osteoarthrosis
None
Mix 30.5 14 MC - Moderate enthesiopathies on right carpus; mild, left-antebrachiocarpal
osteoarthrosis
- Bilateral moderate coxofemoral osteoarthrosis
None
Mix 23.5 10 FS - Moderate bilateral stifle osteoarthrosis and moderate intracapsular
swelling
Carprofen
(2.2 mg/kg)
Mix 28.1 10 FS - Moderate bilateral elbow osteoarthrosis
- Moderate left-stifle osteoarthrosis with intracapsular swelling
Metacam
(0.1 mg/kg
English Bulldog 25.2 8 MC - Severe osteoarthrosis, left elbow
- Moderate intracapsular swelling and mild osteoarthrosis, right stifle
Carprofen
(2 mg/kg BID)
German Shorthaired Pointer 21.5 14 FS - Moderate bilateral elbow osteoarthrosis Carprofen
(2.4 mg/kg BID)
Labrador Retriever 26.1 13 FS - Bilateral severe stifle osteoarthrosis due to cranial cruciate ligament
disease
Meloxicam
(0.1 mg/kg SID)
Mix 18.2 13 FS - Bilateral moderate elbow osteoarthrosis and medial epicondylitis Meloxicam
(0.1 mg/kg SID)
Mix 22 9 FS - Moderate, stifle osteoarthrosis with moderate intracapsular swelling None
Bernese Mountain Dog 50 3 M - Bilateral severe elbow osteoarthritis, medial coronoid disease, and medial
epicondylitis
Carprofen
(2 mg/kg SID)
Belgian Malinois 25.1 9 FS - Severe bilateral elbow osteoarthrosis
- Bilateral moderate hip osteoarthrosis
Carprofen
(2 mg/kg BID)
Mix 28.6 13 FS - Severe bilateral elbow osteoarthritis
- Severe bilateral hip osteoarthritis
None
Border Collie 22 14 MC - Severe thoracolumbosacral osteophytosis
- Multifocal carpal enthesiophytes
None
Beagle 17.6 5 MC - Mild left elbow osteoarthrosis, with possible medial coronoid disease
- Moderate-to-severe bilateral stifle osteoarthrosis
None
FS, female spayed; MC, male castrated; Mix, mixed breed; SID, once daily; BID, twice daily.
delivery vehicle was olive oil which is a food item. The
absorption may be greater and more consistent because of the
oil-based vehicle which may be due to the lipophilic nature
of CBD, hence delivery with food may be preferable (32,33).
As previously demonstrated, CBD biotransformation in dogs
involves hydroxylation, carboxylation and conjugation, leading
to relatively rapid elimination suggesting a more frequent dosing
schedule (34). The dosing schedule of twice per day was chosen
due to the practical nature of this dosing regimen even though
the elimination is well within a three or four time a day dosing
regimen. Our hope was that the lipophilic nature of CBD would
allow for a steady state over time, and future studies examining
24 h pharmacokinetics with different dosing regimens with larger
numbers of dogs, and steady state serum pharmacokinetics after
extended treatment in a clinical population are sorely needed.
The main objective of this study was to perform an owner
and veterinary double-blinded, placebo-controlled, cross-over
study to determine the efficacy of CBD oil in dogs affected by
OA. Despite our small sample size, short study duration and
heterogeneity of OA signs, CBPI and Hudson scores showed that
CBD oil increase comfort and activity in the home environment
for dogs with OA. Additionally, veterinary assessments of
pain were also favorable. Although a caregiver placebo effect
should be considered with subjective evaluations by owners
and veterinarians (35), the cross-over design limits confounding
covariates since each dog serves as its own control. Our statistical
model controlled for the possible effect of treatment sequence.
The lack of a placebo effect in our study may be due to
nine of the 16 owners being intimately involved in veterinary
medical care, all of whom have an understanding of the placebo
effect making them more cognizant of improvements when
providing feedback. In addition, there was a noticeable decrease
in Hudson scores and rise in CBPI scores during the initiation
placebo treatment suggesting a potential carry over effect of
CBD treatment indicating that a longer washout period might
be indicated in future studies. This carry over effect may have
resulted in some improved perceptions at the initiation of the
placebo treatment which were eliminated by week 4 of placebo
treatment, underscoring the importance of longer term steady
state PK studies in dogs.
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Gamble et al. Cannabidiol and Osteoarthritis in Dogs
TABLE 3 | Canine Brief Pain Inventory (Pain and Activity questions) and Hudson Scale mean and standard deviation; lameness, weight-bearing and pain scores median
and ranges at each time for cannabidiol (CBD) and placebo oils.
CBD oil Placebo oil
Week 0 Week 2 Week 4 Week 0 Week 2 Week 4
CBPI Pain (0–40) 21 ±8 14 ±6* 14 ±8* 17 ±7 19 ±9 19 ±9
CBPI activity interference (0–60) 35 ±15 25 ±15* 26 ±14* 27 ±15 29 ±15 31 ±16
Hudson (0–110) 54 ±13 67 ±15* 67 ±10* 65 ±14 64 ±16 60 ±19
Veterinary lameness§ 3 (1–4) 3 (1–4) 3 (1–4) 3 (2–4) 3 (2–4) 3 (1–4)
Veterinary pain R3 (3–4) 3 (2–4)* 3 (1–4)* 3 (2–4)** 3 (2–4) 3 (2–4)**
Veterinary weight-bearing =2 (1–3) 2 (1–3) 2 (1–3) 2 (1–3) 2 (1–3) 2 (1–3)
*Represents significant difference (p <0.05) from baseline week 0 of CBD treatment. **Represents significant differences (p <0.05) from week 2 of CBD oil treatment. §Lameness was
scored as follows: 1 =no lameness observed/walks normally, 2 =slightly lame when walking, 3 =moderately lame when walking, 4 =severely lame when walking, 5 =reluctant to rise
and will not walk more than 5 paces. RPain on palpation was scored as follows: 1 =none, 2 =mild signs, dog turns head in recognition, 3 =moderate signs, dog pulls limb away, 4=
severe signs, dog vocalizes or becomes aggressive, 5 =dog will not allow palpation. =Weight-bearing was scored as follows: 1 =equal on all limbs standing and walking, 2 =normal
standing, favors affected limb when walking, 3 =partial weight-bearing standing and walking, 4 =partial weight-bearing standing, non-weight-bearing walking, 5 =non-weight-bearing
standing and walking.
TABLE 4 | Serum chemistry values of dogs receiving CBD or placebo oils.
Reference CBD oil Placebo oil
Week 0 Week 2 Week 4 Week 0 Week 2 Week 4
Sodium 145–153 mEq/L 149 ±3 149 ±2 149 ±1 149 ±1 149 ±2 149 ±2
Potassium 4.1–5.6 mEq/L 4.9 ±0.3 4.9 ±0.5 4.9 ±0.3 4.8 ±0.4 4.9 ±0.4 4.9 ±0.3
Chloride 105–116 mEq/L 110 ±3 109 ±3 109 ±2 110 ±2 110 ±2 110 ±2
SUN 10–32 mg/dL 20 ±9 20 ±7 20 ±6 19 ±6 21 ±7 19 ±6
Creatinine 0.6–1.4 mg/dL 1.0 ±0.3 1.1 ±0.3* 1.0 ±0.3* 0.9 ±0.3 1.0 ±0.3* 1.0 ±0.3*
Calcium 9.3–11.4 mg/dL 10.4 ±0.5 10.4 ±0.4 10.3 ±0.4 10.4 ±0.6 10.4 ±0.4 10.4 ±0.4
Phosphorus 2.9–5.2 mg/dL 3.8 ±0.8 3.9 ±0.8 3.9 ±0.6 4.0 ±0.7 3.9 ±0.6 4.0 ±0.5
Magnesium 1.4–2.2 mg/dL 1.8 ±0.2 1.8 ±0.2 1.8 ±0.2 1.8 ±0.1 1.8 ±0.1 1.8 ±0.1
Glucose 63–118 mg/dL 92 ±9 89 ±9 92 ±9 97 ±10* 93 ±8 97 ±10*
ALT 20–98 U/L 93 ±86 93 ±88 114 ±119 90 ±89 222 ±606 166 ±284
AST 14–51 U/L 31 ±8 33 ±13 34 ±16 30 ±8 56 ±99 45 ±34
ALP 17–111 U/L 160 ±212 238 ±268 323 ±407* 204 ±287 186 ±287 175 ±248
GGT 0–6 U/L 4 ±3 3 ±2 3 ±2 3 ±2 4 ±6 5 ±4
Bilirubin 0.0–0.2 mg/dL 0.1 ±0.1 0.0 ±0.1 0.1 ±0.1 0.0 ±0.1 0.0 ±0.1 0.0 ±0.1
Total protein 5.3–7.0 g/dL 6.3 ±0.4 6.4 ±0.5 6.3 ±0.4 6.3 ±0.4 6.3 ±0.4 6.3 ±0.4
Albumin 3.1–4.2 g/dL 3.7 ±0.2 3.7 ±0.2 3.7 ±0.2 3.7 ±0.2 3.7 ±0.2 3.7 ±0.2
Globulin 1.9–3.6 g/dL 2.6 ±0.3 2.6 ±0.4 2.6 ±0.4 2.6 ±0.4 2.6 ±0.4 2.6 ±0.4
Cholesterol 138–332mg/dL 291 ±64 301 ±62 302 ±62 295 ±71 300 ±71 308 ±83
CK 48–260 U/L 148 ±81 147 ±59 134 ±61 139 ±57 158 ±80 168 ±105
Data presented at mean +standard deviations. Asterisk (*) indicates significantly different (p <0.05) serum concentration from baseline week 0 CBD treatment. SUN , serum urea
nitrogen; ALT, alanine animotranferase; AST, aspartate animotransferase; ALP, alkaline phosphatase; GGT, gamma glutamyl transferase; CK, creatine kinase.
There was no significant difference in subjective veterinary
lameness score and weight-bearing capacity throughout the
study. Kinetic data was obtained from these dogs (data not
shown), however 11 of the 16 dogs had significant bilateral
disease (stifle, coxofemoral, or elbow) making evaluation of peak
vertical force or symmetry tenuous at best. Unilateral disease in
any of the aforementioned joints would be ideal to study the
kinetic effects of this or similar extracts for pain relief leading
to better objective outcomes. The population we used in our
investigation was representative of dogs presenting in a clinical
setting for management of OA and represents the typical OA
patient.
Currently, NSAIDs are the primary treatment for OA and
are associated with negative effects on the gastrointestinal tract
and glomerular filtration (2). In the current study, no significant
difference was noted in BUN, creatinine, or phosphorus between
dogs treated with the CBD oil vs. the placebo oil, while
NSAID treatment resulted in a higher creatinine concentration.
A mild rise in creatinine from baseline was noted in both
groups at weeks 2 and 4, the hydration status of the dogs was
Frontiers in Veterinary Science | www.frontiersin.org 6July 2018 | Volume 5 | Article 165
Gamble et al. Cannabidiol and Osteoarthritis in Dogs
FIGURE 1 | Box-and-whisker plot of serum alkaline phosphatase (ALP) activity
at each time for treatment and placebo oils. Box represents the mean and 25th
and 75th percentile and the whiskers represent the 99th and 1st percentiles.
*Indicates a significant difference (p<0.05) from week 0 CBD treatment.
unknown; however changes in albumin sodium, and chloride
were unchanged suggesting euhydration, and all creatinine
values remained within the reference interval. Increased ALP
activity is fairly sensitive for hepatobiliary changes in this age
group, but not specific. Increased ALP activity noted in nine
dogs in the CBD treatment group may be an effect of the
hemp extract attributed to the induction of cytochrome p450
mediated oxidative metabolism of the liver (reported previously
with prolonged exposure to cannabis) (36–38). Other causes
of cholestasis, increased endogenous corticosteroid release from
stress, or a progression of regenerative nodular hyperplasia of
the liver cannot be ruled out. Without concurrent significant
rise in ALT in the CBD treatment to support hepatocellular
damage, or biopsy for further clarification, the significance is
uncertain. As such, it may be prudent to monitor liver enzyme
values (especially ALP) while dogs are receiving industrial hemp
products until controlled long term safety studies are published.
A recent survey reported that pet owners endorse hemp
based treats and products because of perceived improvement
in numerous ailments, as hemp products were moderately to
very helpful medicinally (39). Some of the conditions thought
to be relieved by hemp consumption were: pain, inflammation,
anxiety and phobia, digestive system issue, and pruritus (39).
One immunohistochemical study suggested that cannabinoids
could protect against the effects of immune-mediated and
inflammatory allergic disorders in dogs (40) whereas another
uncontrolled study suggested that CBD has anticonvulsant
and anti-epileptic properties in dogs (41). The apparent
analgesic effect of the industrial hemp based oil observed
in the present study may be attributable to downregulation
of cylooxygenase enzymes, glycine interneuron potentiation,
transient receptor potential cation receptor subfamily V1
receptor agonism (peripheral nerves), and/or g-protein receptor
55 activation (immune cells), influencing nociceptive signaling
and/or inflammation (14,42,43).
The industrial hemp product used in this study is a proprietary
strain-specific extract of the cannabinoids outlined in the
methods with relatively high concentrations of CBD and lesser
quantities of other cannabinoids as well as small amounts of
terpenes that may have synergistic effects often termed the
“entourage effect.” This brings to light that fact that different
strains of cannabis produce differing amounts of CBD and other
related cannabinoids making the results of this study specific
to this industrial hemp extract that may not translate to other
available products due to differing cannabinoid concentrations
in this largely unregulated market.
In conclusion, this particular product was shown to be
bioavailable across the small number of dogs examined in the PK
portion of the study, and dogs with OA receiving this industrial
hemp extract high in CBD (2 mg/kg of CBD) were perceived to
be more comfortable and active. There appear to be no observed
side effects of the treatment in either the dogs utilized in the PK
study at 2 and 8 mg/kg, or dogs undergoing OA treatment for
a month duration. There were some dogs with incidental rises
in alkaline phosphatase that could be related to the treatment.
Further long-term studies with larger populations are needed to
identify long-term effects of CBD rich industrial hemp treatment,
however short term effects appear to be positive.
AUTHOR CONTRIBUTIONS
L-JG was responsible for data analysis and interpretation,
drafting of the manuscript and approval of the submitted
manuscript. JB was responsible for the conception of the study
and manuscript writing and revisions. CF was responsible for
acquisition of data and manuscript revision. WS was responsible
for pharmacokinetic evaluation and revision of the manuscript.
SM was responsible for statistical analysis, data analysis and
revision of the manuscript. LW was responsible for laboratory
work including liquid chromatography-mass spectrometry. HB
was responsible for interpretation of the blood work and
manuscript revision. EB was responsible for acquisition of data,
and data analysis. JW was responsible for the conception of study,
supervised data collection, statistical analysis, and manuscript
editing.
FUNDING
Ellevet LLC supported this research with a grant to Cornell
University to study this product.
ACKNOWLEDGMENTS
The authors would like to thank Renee C. Staffeld and Danny
Sack for data entry. The present study was financially supported
by ElleVet Sciences, Portland, Maine.
Frontiers in Veterinary Science | www.frontiersin.org 7July 2018 | Volume 5 | Article 165
Gamble et al. Cannabidiol and Osteoarthritis in Dogs
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Conflict of Interest Statement: The 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 © 2018 Gamble, Boesch, Frye, Schwark, Mann, Wolfe, Brown, Berthelsen
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