Have you ever wondered if your furry friend might get “drug tested” at the vet? With marijuana legalization expanding across the country and pet toxicity cases on the rise, this question is becoming increasingly common. As a pet parent, I wanted to dive into this topic to help other dog owners understand what’s really happening when vets suspect drug exposure in our canine companions.
The Reality of Veterinary Drug Testing
Let me start by saying something important – veterinarians don’t routinely “drug test” dogs like employers might test humans. Instead, they perform toxicology tests when they suspect your pet has been exposed to something harmful. These tests are conducted for your dog’s wellbeing, not to get anyone in trouble.
When a dog shows symptoms like disorientation, unusual lethargy, or other concerning behaviors, vets might suspect toxin exposure. In these cases they’re focused on treating your pet not reporting you to authorities.
Why Vets Might Test for Drugs in Dogs
The main reasons vets test for drugs in dogs include:
- Confirming suspected exposure: When a pet shows symptoms consistent with drug toxicity
- Determining appropriate treatment: Different substances require different approaches
- Ruling out other medical conditions: Some neurological issues can mimic drug exposure
- Medical documentation: For the pet’s health record
According to recent data, veterinary emergency rooms are seeing a significant increase in marijuana toxicosis cases as legalization expands Many of these cases are unwitnessed, with owners unaware of how their pet gained access to such substances
Common Substances Vets Test For
While marijuana is a common concern vets might test for various substances depending on the symptoms
- THC (from marijuana)
- Prescription medications
- Over-the-counter medications
- Household toxins
- Certain foods (like chocolate or xylitol)
How Do Veterinary Drug Tests Work?
When your vet suspects drug exposure, they might use several testing methods:
1. Urine Drug Screening Tests
Many veterinarians use human urine drug screening tests as they’re the only readily available bedside option. However, recent findings from Tufts University’s Cummings School of Veterinary Medicine call their reliability into question for several reasons:
- These tests were designed for human metabolism patterns, not canine ones
- Dogs metabolize THC differently, producing additional metabolites not found in humans
- A negative test doesn’t necessarily rule out exposure
- Sample handling issues can lead to false negatives (THC can bind to glass and rubber in collection containers)
2. Blood Tests
More comprehensive blood tests might be ordered to check for:
- Organ function (to assess damage)
- Electrolyte imbalances
- Other markers of toxicity
3. Clinical Assessment
Often, vets rely heavily on clinical signs and symptoms to make a diagnosis:
- Unusual gait or coordination problems
- Changes in heart rate
- Urinary incontinence
- Abnormal reactions to stimuli
- Excessive drooling or vomiting
Signs of Marijuana Toxicosis in Dogs
Since marijuana exposure is becoming more common, it’s worth knowing the signs. According to veterinarians surveyed, the most common clinical signs include:
- Urinary incontinence
- Disorientation
- “Drunken” gait
- Lethargy
- Hyperesthesia (increased reactivity)
- Low heart rate
For synthetic marijuana cases, symptoms may be more severe and can include tremors and seizures.
What Happens When a Dog Tests Positive?
If your dog tests positive for drug exposure, don’t panic! Vets aren’t required to report these cases to authorities in most situations. Their primary concern is treating your pet.
Treatment typically involves:
For Mild to Moderate Cases:
- Supportive care
- IV fluids
- Monitoring
- Temperature regulation
- A safe, quiet environment
For Severe Cases:
- More intensive care may be required
- Intravenous lipid therapy (though this remains controversial)
- Hemodialysis in extreme cases
- Respiratory support if needed
The good news is that for mild to moderate cases, the prognosis is excellent. Most pets make a full recovery with proper care.
Legal Considerations for Pet Owners
While vets generally don’t report drug exposure to authorities, there are some important legal considerations:
- In cases of suspected deliberate harm or neglect, vets may be mandatorily required to report
- Being honest with your vet about possible exposure helps them treat your pet more effectively
- The vet-client relationship is generally confidential, similar to doctor-patient relationships
How to Prevent Accidental Drug Exposure
Prevention is always better than treatment. Here are some steps to keep your dog safe:
- Secure all medications: Keep all drugs, recreational or prescription, in locked cabinets
- Be careful with edibles: Store edible marijuana products where pets absolutely cannot access them
- Proper disposal: Dispose of remnants securely where pets can’t get them
- Kitchen safety: If cooking with cannabis products, immediately remove trash and clean all surfaces
- Outdoor awareness: Watch your dog closely on walks to prevent them from ingesting unknown substances
What To Do If You Suspect Drug Exposure
If you think your dog may have been exposed to marijuana or other drugs:
- Call your vet immediately – don’t wait for symptoms to worsen
- Be honest about possible exposure – this helps your vet provide proper treatment
- Don’t induce vomiting without professional guidance – this can sometimes make things worse
- Note when exposure may have occurred – timeline helps with treatment decisions
- Bring packaging if available – knowing the exact substance helps determine treatment
Research Advancements in Veterinary Toxicology
The field of veterinary toxicology is evolving. Tufts University’s Cummings School is currently conducting research, including a randomized controlled trial examining the efficacy of intravenous lipid therapy for moderate to severe marijuana toxicosis in dogs.
As our understanding improves, so will testing and treatment options for our furry friends.
FAQs About Dog Drug Testing
Can vets tell if my dog has been around marijuana smoke?
While secondhand marijuana smoke exposure is possible, it generally causes milder symptoms than direct ingestion. Vets focus on treating symptoms regardless of exposure method.
Will my vet report me if my dog tests positive for drugs?
Generally no. Veterinarians are focused on treating your pet, not reporting drug use. However, cases of suspected intentional harm might be reported to authorities.
How long do drugs stay in a dog’s system?
This varies by substance, but marijuana effects can last up to 72 hours in dogs, much longer than in humans.
Can CBD products cause positive drug tests in dogs?
Some CBD products contain trace amounts of THC which could potentially cause mild symptoms, but pure CBD products shouldn’t cause toxicity.
How accurate are veterinary drug tests?
As mentioned earlier, the common urine tests have limitations when used in dogs. False negatives are possible due to differences in how dogs metabolize substances.
Final Thoughts
So, do vets drug test dogs? Not in the way you might think. They test for toxins when necessary to provide proper medical care. If your dog has been exposed to marijuana or other substances, being honest with your vet is the best approach – they’re there to help your pet, not judge you.
As pet parents, our primary responsibility is keeping our furry family members safe. With marijuana products becoming more common in homes, taking extra precautions to prevent accidental ingestion is increasingly important.
Remember, your vet has probably seen it all before. Their priority is your pet’s health, not your personal choices. By being transparent about possible exposures, you’re helping them provide the best care possible for your four-legged friend.
Have you ever had an experience with suspected toxicity in your dog? I’d love to hear your stories in the comments below!
Alyson H Fitzgerald1Veterinary Diagnostic Laboratory, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USAFind articles by
Issue date 2021 Sep. © 2021 The Author(s)
Veterinarians diagnose marijuana toxicity based on clinical signs and history, or in conjunction with an over-the-counter (OTC) human urine drug screen. With the legalization of recreational marijuana use becoming more prevalent in the United States, a more accurate test to aid in the diagnosis of canine marijuana toxicity is needed. We collected urine and serum samples from 19 dogs with confirmed or suspected marijuana toxicosis from multiple veterinary hospitals and analyzed them with a novel UPLC-MS/MS method. Calibrations from 0.1 to 100 ng/mL and QC materials were prepared. Samples were extracted, purified, and eluted with solid-phase extraction. Urine samples were tested with an OTC human urine drug screen. The limit of detection (LOD) and lower limit of quantification (LLOQ) ranges for marijuana metabolites in serum were 0.05–0.25 ng/mL and 0.1–0.5 ng/mL, respectively. In urine, the LOD and LLOQ ranges for the metabolites were 0.05–0.1 ng/mL and 0.1–0.5 ng/mL, respectively. In serum, median and range of metabolite concentrations (ng/mL) detected included: THC, 65.0 (0.14–160); 11-OH-Δ9-THC, 4.78 (1.15–17.8); 11-nor-9-carboxy-Δ9-THC, 2.18 (0.71–7.79); CBD, 0.28 (0.11–82.5); and THC-glucuronide, 2.05 (0.72–18.3). In the 19 urine samples, metabolite: creatinine (ng: mg) values detected included: THC, 0.22 (0.05–0.74); 11-OH-Δ9-THC, 0; 11-nor-9-carboxy-Δ9-THC, 1.32 (0.16–11.2); CBD, 0.19 (0.12–0.26); THC-COOH-glucuronide, 0.08 (0.04–0.11); and THC-glucuronide, 0.98 (0.25–10.7). Twenty of 21 urine samples tested negative for THC on the urine drug screen. All 19 serum samples contained quantifiable concentrations of THC using our novel UPLC-MS/MS method. Utilizing a UPLC-MS/MS method can be a useful aid in the diagnosis of marijuana toxicosis in dogs, whereas using an OTC human urine drug test is not a useful test for confirming marijuana exposure in dogs because of the low concentration of THC-COOH in urine.
Keywords: cannabidiol, cannabis, chromatography, dogs, dronabinol, marijuana
Marijuana (Cannabis sativa) is a plant that has been used medicinally and recreationally for centuries.3,5 Tetrahydrocannabinol (THC) is the main constituent that is responsible for the psychoactive effects, and cannabidiol (CBD) is the primary non-psychoactive metabolite.3,5 Thirty percent of the states in the United States have legalized recreational marijuana, and this could lead to more canine exposures with the increasing availability of the drug to the public.4 Dogs are most commonly exposed to marijuana via ingestion of the plant material or edible marijuana products.3,14 Most intoxications are not lethal but can result in severe clinical signs that require patient care.9,12 One retrospective study evaluated a cohort of 125 dogs in Colorado and reported a positive correlation between the number of marijuana toxicoses in dogs and the number of medical marijuana licenses issued from 2005 to 2010.12 Additionally, the concentration of THC in cannabis samples seized by the Drug Enforcement Administration from 1995 to 2018 has more than tripled,11 which may explain the high morbidity associated with marijuana exposure in dogs, prompting their owners to seek medical attention for their pets.
Common clinical signs of marijuana intoxication in dogs include ataxia, urine dribbling, depression, mydriasis, and hyperesthesia.3,5,9,12,14 The nonspecific signs of marijuana toxicity pose a diagnostic challenge to the clinician if the owner is unaware or reluctant to discuss exposure.16 Confirmatory tests are largely unavailable for suspected marijuana intoxication in dogs. Some clinicians utilize an over-the-counter (OTC) human urine drug screen that most commonly measures 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (THC-COOH); however, the canine marijuana metabolite profile is unknown.16
We quantified marijuana metabolites in serum and urine of dogs that had been presented because of suspected marijuana toxicity. The main human marijuana metabolites are 11-hydroxy-Δ9-tetrahydrocannabinol (11-OH-THC), THC-COOH, and CBD.8 Our primary objective was to detect and quantify marijuana compounds in otherwise healthy dogs exposed to marijuana by developing and validating an ultra-performance liquid chromatography–tandem mass spectrometer (UPLC-MS/MS) method. Our secondary objective was to evaluate the usefulness of a human urine drug screen in detecting marijuana and its related products in otherwise healthy but exposed dogs. Our hypothesis was that, upon marijuana exposure, dogs produce low or negligible amounts of THC-COOH in urine compared to other metabolites, leading to a high proportion of false-negative tests when using the OTC human urine drug test.
We enrolled in our pilot study otherwise healthy dogs that had been presented with known (owner-observed exposure) or suspected (based on clinical signs and history) marijuana ingestion to the Kansas State University Veterinary Health Center (KSU-VHC; Manhattan, KS, USA), University of Illinois Veterinary Teaching Hospital (UI-VTH; Urbana, IL, USA), and 2 private practices (Animal ER of University Park, Bradenton, FL, USA [Animal ER] and Veterinary Emergency + Critical Care, Las Vegas, NV, USA [VECC]). Institutional Animal Care and Use Committee (IACUC) approval was obtained at the 2 universities, and client consent was obtained from all dog owners prior to enrollment. We included 21 dogs in our study: 19 dogs with clinical signs of marijuana toxicity and 2 client-owned dogs with no known exposure to marijuana, which were included to verify that there were no endogenous metabolites that could be misidentified as metabolites of interest. We collected ~3 mL of blood from a peripheral vein and 5 mL of urine by cystocentesis or voiding from each dog. Serum and urine samples were shipped overnight on ice to the Kansas State Veterinary Diagnostic Laboratory and were stored at −80°C for up to 6 mo until analysis.7,13,15 Urine marijuana metabolites were standardized to urine creatinine for each patient. Urine creatinine was measured via the Jaffe method (Cobas c501; Roche). Urine samples, at room temperature, were tested by an OTC human urine drug screen (iScreen 2 panel drug test THC/coc; AlcoPro) to detect THC (THC-COOH target analyte).2
The following standards were utilized: THC, THC-d3, 11-OH-THC, 11-OH-THC-d3, THC-COOH, THC-COOH-d3, CBD, CBD-d3, THC-COOH-glu, THC-COOH-glu-d3 (all from MilliporeSigma), and THC-glu (ElSohly Laboratories). Sera and urine samples, calibrators, blanks (negative dog serum or urine), and quality controls (QC) were extracted and cleaned-up by solid-phase extraction (SPE; Oasis HLB Prime µElution 96-well plates; Waters). For serum samples, 100 µL of each calibration working solution, QC solution, and the serum sample were added to a 1.5-mL centrifuge tube, respectively. A 50-µL aliquot of the internal standard (IS) solution was placed into each centrifuge tube along with 150 µL of 0.1% formic acid in acetonitrile, vortexed for 10 s, and centrifuged for 10 min at 13,000 × g at 4°C. For urine samples, 100 µL of each calibrator working solution, QC solution, and the urine sample were added into a 48-well non–tissue culture-treated plate. Fifty µL of the IS solution was placed into each well along with 150 µL of 0.1% formic acid in acetonitrile. Subsequently, the plate was shaken for 20 min and centrifuged at 2,000 × g for 30 min at room temperature. The supernatant was transferred to a new centrifuge tube and diluted with 400 µL of water. The diluted sample was placed into a 96-well plate. Following a wash with 2 × 250 µL of 25% methanol, the components were eluted with 50 µL of 90/10 acetonitrile/methanol. Fifty μL of 0.1% formic acid were added onto each well of the 96-well collection plates before the UPLC-MS/MS analyses.
Concentrations of the marijuana metabolites in serum and urine samples were determined (Xevo TQ-S triple quadrupole mass spectrometer; Waters; Fig. 1, Suppl. Fig 1). Briefly, an Acquity UPLC HSS T3 column (1.8 μm, 2.1 × 50 mm) was held at 45°C with eluents composed of mobile phase A (0.1% formic acid in water) and mobile phase B (0.1% formic acid in acetonitrile). The flow rate was 0.4 mL/min. The following gradient program was used: from 0 to 3.5 min phase A (25–5%), at 3.5 min phase A (5%), hold for 0.5 min, and at 4.2 min phase A (25% for 0.8 min). A positive ionization mode was used (+ESI).1,8 The ions were monitored using multiple reaction monitoring (MRM) mode (Table 1).
Multiple reaction monitoring (MRM) chromatograms from analysis of a negative control dog serum. A, C, E, G, I, and K in the left panel are the MRM chromatograms of negative canine serum. B, D, F, H, J, and L in the right panel are the MRM chromatograms of cannabinoids (CBD, THC, 11-OH-THC, THC-COOH, THC-glu, THC-COOH-glu, respectively) spiked at 10 ng/mL in negative canine serum.
Multiple reaction monitoring method development transition ions for each cannabinoid in canine serum and urine.
| Metabolite | Qualifier ion | Quantifier ion |
|---|---|---|
| CBD | 315.237 → 135.180 | 315.237 → 193.139 |
| CBD-d3 | 318.257 → 138.217 | 318.257 → 196.176 |
| THC | 315.252 → 135.167 | 315.252 → 192.992 |
| THC-d3 | 318.258 → 138.168 | 318.258 → 195.993 |
| 11-OH-THC | 331.253 → 193.060 | 331.258 → 313.138 |
| 11-OH-THC-d3 | 334.258 → 196.060 | 334.258 → 316.138 |
| THC-COOH | 345.223 → 192.995 | 345.223 → 299.087 |
| THC-COOH-d3 | 348.223 → 302.082 | 348.223 → 195.990 |
| THC-glu | 491.470 → 177.200 | 491.470 → 315.300 |
| THC-COOH-glu | 521.474 → 301.300 | 521.474 → 345.363 |
| THC-COOH-glu-d3 | 524.494 → 304.169 | 524.494 → 348.234 |
The developed method was validated in reference partly to the FDA guidelines for the Bioanalytical Method Validation Guidance for Industry, with precision ≤20% and accuracy of 80–120%.17 A signal-to-noise ratio of 3:1 was generally considered acceptable for estimating the limit of detection (LOD). A typical signal-to-noise ratio of 10:1 of the analyte in the negative control sample was considered acceptable for estimating the lower limit of quantification (LLOQ). For serum samples, the calibration curve was linear from 0.1 (CBD and THC) or 0.5 (11-OH-THC, THC-COOH, and THC-glu) to 100 ng/mL with a correlation coefficient (R2) of at least 0.99. For urine samples, the calibration curve was linear from 0.1 (CBD and THC), 0.25 (11-OH-THC and THC-COOH) or 0.5 (THC-glu and THC-COOH-glu) to 100 ng/mL with R2 of at least 0.99 (Table 2). For serum, deviations in QC samples (n = 9) were <11.4% of nominal concentrations for all of the compounds. The accuracy of the assay for different analytes was 93.4–112% of their nominal values for calibrators. For urine, deviations in QC samples (n = 9) were <16.8% of nominal concentrations for all of the compounds. The accuracy of the assay for different analytes was 84.0–110% of their nominal values for calibrators.
Limit of detection (LOD) and lower limit of quantification (LLOQ) for cannabinoids in canine serum and urine (ng/mL).
| THC | 11-OH-THC | THC-COOH | CBD | THC-glu | THC-COOH-glu | |
|---|---|---|---|---|---|---|
| Serum | ||||||
| LOD | 0.05 | 0.10 | 0.10 | 0.05 | 0.25 | |
| LLOQ | 0.10 | 0.5 | 0.5 | 0.10 | 0.50 | |
| Urine | ||||||
| LOD | 0.05 | 0.10 | 0.10 | 0.05 | 0.10 | 0.10 |
| LLOQ | 0.10 | 0.25 | 0.25 | 0.10 | 0.50 | 0.50 |
The 21 canine serum/urine pairs included: 2 negative controls, 6 confirmed marijuana exposures, and 13 suspected exposures (Suppl. Table 1). No one breed was overrepresented. Cases were presented to KSU-VHC (5), VECC (10), Animal ER (2), and UI-VTH (2; Suppl. Table 1). The concentration of THC in serum, although different numerically, was not statistically significant (p = 0.25) by institution (data not shown).
In serum, THC was detected in all 19 samples from confirmed and suspected marijuana cases (Table 3). The 2 dogs without exposure to marijuana had undetectable concentrations of the cannabinoids in sera. The median concentration of THC detected was 65.0 ng/mL (0.14–160 ng/mL ± SD 47.6). 11-OH-THC was detected in 16 of 19 serum samples, and the median concentration was 4.8 ng/mL (1.15–17.8 ng/mL ± 5.0). THC-COOH was detected in 17 of 19 serum samples, and the median concentration was 2.18 ng/mL (0.71–7.79 ng/mL ± 2.61). CBD was detected in 12 of 19 serum samples, and the median concentration was 0.28 ng/mL (0.11–82.5 ng/mL ± 23.9). Two samples had >100-fold higher concentrations of CBD than the other 17 samples that were similar in concentration and were 0.1–0.4 ng/mL (Suppl. Table 2). THC-glu was detected in 16 of 19 serum samples, and the median concentration was 2.05 ng/mL (0.72–18.3 ng/mL ± 4.58).
Descriptive statistics for cannabinoid metabolites (ng/mL) detected in canine serum samples.
| Metabolite | No. of samples | Mean | Median | SD | Minimum | Maximum |
|---|---|---|---|---|---|---|
| THC | 19 | 68.0 | 65.0 | 47.6 | 0.14 | 160 |
| 11-OH-THC | 16 | 6.12 | 4.78 | 5.02 | 1.15 | 17.9 |
| THC-COOH | 17 | 3.52 | 2.18 | 2.61 | 0.71 | 7.79 |
| CBD | 12 | 8.70 | 0.28 | 23.9 | 0.11 | 82.5 |
| THC-glu | 16 | 4.14 | 2.05 | 4.58 | 0.72 | 18.3 |
In urine, no metabolite was detected consistently in all samples (Table 4). THC was detected in 8 of 19 urine samples, and the median concentration was 0.24 ng/mL (0.17–2.74 ng/mL ± 0.94). 11-OH-THC was not detected in any sample. THC-COOH was detected in 16 of 19 urine samples, and the median concentration was 1.84 ng/mL (0.33–16.8 ng/mL ± 5.48). Both CBD and THC-COOH-glu were detected in 2 of 19 urine samples at <1 ng/mL. THC-glu was detected in 15 of 19 urine samples, and the median concentration was 1.23 ng/mL (0.42–11.1 ng/mL ± 3.74). Urine metabolites were also standardized to urine creatinine (Table 5; Suppl. Table 3).
Descriptive statistics for cannabinoid metabolites (ng/mL) detected in canine urine samples.
| Metabolite | No. of samples | Mean | Median | SD | Minimum | Maximum |
|---|---|---|---|---|---|---|
| THC | 8 | 0.74 | 0.24 | 0.94 | 0.17 | 2.74 |
| 11-OH-THC | 0 | ND | ND | ND | ND | ND |
| THC-COOH | 16 | 4.68 | 1.84 | 5.48 | 0.33 | 16.8 |
| CBD | 2 | 0.36 | 0.36 | 0.27 | 0.16 | 0.55 |
| THC-COOH-glu | 2 | 0.29 | 0.29 | 0.01 | 0.28 | 0.29 |
| THC-glu | 15 | 3.53 | 1.23 | 3.74 | 0.42 | 11.1 |
Descriptive statistics for cannabinoid metabolite:creatinine ratios detected in canine urine samples (ng metabolite:mg creatinine).
| Metabolite | No. of samples | Mean | Median | SD | Minimum | Maximum |
|---|---|---|---|---|---|---|
| THC:Cre | 8 | 0.28 | 0.22 | 0.22 | 0.05 | 0.74 |
| 11-OH-THC:Cre | 0 | ND | ND | ND | ND | ND |
| THC-COOH:Cre | 16 | 3.23 | 1.32 | 3.76 | 0.16 | 11.2 |
| CBD:Cre | 3 | 0.19 | 0.19 | 0.10 | 0.12 | 0.26 |
| THC-COOH-glu:Cre | 2 | 0.08 | 0.08 | 0.05 | 0.04 | 0.11 |
| THC-glu:Cre | 15 | 2.75 | 0.98 | 3.21 | 0.25 | 10.7 |
Of the 21 urine samples tested with the OTC human urine drug test, 20 were negative (Suppl. Figs. 2–21). One urine sample was unable to be run on the OTC human drug test because of an insufficient volume of urine; however, on HPLC-MS/MS, THC-COOH was detected at 2.19 ng/mL, which is well below the 50 ng/mL threshold of the drug screen (Suppl. Table 4). The 2 dogs without exposure to marijuana had undetectable concentrations of the cannabinoids in urine on the OTC test.
All 19 clinical serum samples contained quantifiable concentrations of THC (Table 3), with one sample containing <1 ng/mL THC (above the LLOQ, 0.1 ng/mL; Suppl. Table 2). The primary human metabolite in serum, 11-OH-THC, was consistently detected at >1 ng/mL in all clinical serum samples. In one report, researchers orally administered a cannabis oil extract containing a mixture of 20% THC and 0.5% CBD (1.5 and 0.04 mg/kg, respectively) to 6 dogs and were unable to detect either 11-OH-THC or THC-COOH in serum using HPLC.10 Other metabolites THC-COOH, CBD, and THC-glu were detected frequently (>50% of samples), but at lower median concentrations. THC-COOH-glu was not included in the serum metabolite profile because of poor recovery, but this was not a problem when quantifying this metabolite in urine. Measuring THC directly in serum of affected dogs revealed an ~10-fold higher median concentration compared to other metabolites in the panel (Table 3). Given that higher concentrations of THC were detected in serum in this group of dogs, utilizing a single serum-based assay with THC as the target analyte could prove more reliable compared to utilizing any other analyte of interest or urine-based assays. However, using a panel of analytes in serum and urine such as in the UPLC-MS/MS method described here will increase the sensitivity of detection because of the variability in canine THC metabolism and time of presentation from time of exposure. The variability in canine THC metabolism is not well understood, but in general it has a long-reported half-life of 30 h.5,9 In a clinical setting, it may be helpful to interpret the marijuana metabolite panel as a whole in order to arrive at a diagnosis.
Dogs included in our study produced variable and lower concentrations of cannabinoids in urine compared to sera. THC-COOH and THC-glu were most frequently detected in urine (16 of 19 and 15 of 19, respectively; Tables 3, 4). Three dogs with detectable cannabinoids in sera did not have detectable concentrations of cannabinoids in urine. THC was detected in 8 of 19 urine samples at low but quantifiable concentrations. A small-scale, canine marijuana pharmacokinetic study produced in the 1970s reported that only a small amount of THC was eliminated in the urine unchanged, and as a result of enterohepatic recirculation, more complex, conjugated metabolites were eliminated in urine.6 Unlike humans, dogs with marijuana exposure do not seem to produce large quantities of THC-COOH in urine. Most OTC human urine drug screens can qualitatively detect THC-COOH when the concentration is >50 ng/mL, which was not sensitive enough for this sample of dogs exposed to marijuana.
Limitations of our study include a small sample size from multiple veterinary hospitals and the inability to accurately record the magnitude of marijuana exposure, type of cannabis product, duration of ingestion to time of presentation, and the reluctance or inability of owners to describe or quantify the ingestion. Our results indicate that a UPLC-MS/MS method can be a useful aid in diagnosing marijuana toxicosis in dogs, whereas using an OTC human urine drug test is not a useful test for confirming marijuana exposure in dogs because of the low content of THC-COOH in urine.
Supplemental material, sj-pdf-1-vdi-10.1177_10406387211027227 for Detecting and quantifying marijuana metabolites in serum and urine of 19 dogs affected by marijuana toxicity by Alyson H. Fitzgerald, Yuntao Zhang, Scott Fritz, William H. Whitehouse, Tamera Brabson, Lisa Pohlman, Natalia Cernicchiaro, Caroline Tonozzi and Steve Ensley in Journal of Veterinary Diagnostic Investigation
Abbreviations: 11-OH-THC:Cre = 11-hydroxy-Δ9-tetrahydrocannabinol:creatinine
Animal ER = Animal ER of University Park
CBD:Cre = cannabidiol:creatinine
IS = internal standard
KSU-VHC = Kansas State University Veterinary Health Center
QC = quality control
THC-COOH:Cre = 11-nor-9-carboxy-Δ9-tetrahydrocannabinol: creatinine
THC-COOH-Cre = tetrahydrocannabinol carboxylic acid glucuronide: creatinine
THC-COOH-glu = tetrahydrocannabinol carboxylic acid glucuronide
THC-Cre = Δ9-tetrahydrocannabinol:creatinine
THC-glu:Cre = tetrahydrocannabinol glucuronide:creatinine
THC-glu = tetrahydrocannabinol glucuronide
UI-VTH = University of Illinois Veterinary Teaching Hospital
UPLC-MS/MS = ultra-performance liquid chromatography–tandem mass spectrometer
VECC = Veterinary Emergency + Critical Care
Declaration of conflicting interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: Internal funding was provided by the Kansas State Veterinary Diagnostic Laboratory.
ORCID iDs: Alyson H. Fitzgerald 
https://orcid.org/0000-0002-2899-3564
William H. Whitehouse https://orcid.org/0000-0002-6080-2684
Supplemental material: Supplemental material for this article is available online.
Alyson H. Fitzgerald, Veterinary Diagnostic Laboratory, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USA.
Yuntao Zhang, Veterinary Diagnostic Laboratory, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USA.
Scott Fritz, Veterinary Diagnostic Laboratory, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USA.
William H. Whitehouse, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USA
Tamera Brabson, Las Vegas Veterinary Specialty Center, Las Vegas, NV, USA.
Lisa Pohlman, Veterinary Diagnostic Laboratory, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USA.
Natalia Cernicchiaro, Veterinary Diagnostic Laboratory, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USA.
Caroline Tonozzi, Department of Veterinary Clinical Medicine, University of Illinois at Urbana-Champaign, College of Veterinary Medicine, Urbana, IL, USA.
Steve Ensley, Veterinary Diagnostic Laboratory, Department of Clinical Sciences, Kansas State University, College of Veterinary Medicine, Manhattan, KS, USA.
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplemental material, sj-pdf-1-vdi-10.1177_10406387211027227 for Detecting and quantifying marijuana metabolites in serum and urine of 19 dogs affected by marijuana toxicity by Alyson H. Fitzgerald, Yuntao Zhang, Scott Fritz, William H. Whitehouse, Tamera Brabson, Lisa Pohlman, Natalia Cernicchiaro, Caroline Tonozzi and Steve Ensley in Journal of Veterinary Diagnostic Investigation
Articles from Journal of Veterinary Diagnostic Investigation : Official Publication of the American Association of Veterinary Laboratory Diagnosticians, Inc are provided here courtesy of SAGE Publications