Analysis of cannabinoids in plasma from 38 cases of suspected cannabinoid intoxication in dogs.

Objective: To quantify and characterize plasma cannabinoid concentrations in cases of suspected cannabis toxicity in dogs, identify potential correlations between clinical signs and plasma concentrations, and assess the specificity of cannabis toxicity diagnosis based on clinical signs alone.

Design: Observational study.

Setting: Veterinary teaching hospital.

Animals: Thirty-eight client-owned animals.

Interventions: Blood was collected from dogs presenting to the emergency room for suspected cannabinoid intoxication based on history or physical examination findings. Samples were analyzed using a validated liquid chromatography-tandem mass spectrometry method for the cannabinoids Δ⁹-tetrahydrocannabinol (THC), cannabidiol (CBD), and their active metabolites.

Measurements and main results: The most common abnormality observed was ataxia (35/38 dogs), with urinary incontinence, lethargy, and hyperesthesia also commonly noted. Cannabinoids were quantifiable in 37 of 38 plasma samples (97.4%), with THC the predominant cannabinoid (range: 1.99-2748 ng/mL). Lower concentrations of CBD (up to 115.3 ng/mL) and cannabinoid metabolites were detected. Of the clinical signs recorded, only abnormal reflexes were statistically correlated with the THC concentration at the time of sampling (P = 0.01).

Conclusions: A diagnosis of suspected cannabinoid toxicity based on case history and clinical presentation was confirmed via quantifiable plasma concentrations in nearly all cases. Although the range of plasma cannabinoid concentrations was broad, the clinical signs observed were generally similar. Other than the presence of abnormal reflexes, clinical signs were not associated with plasma THC concentrations. Subsequent confirmation of cannabinoids in plasma indicates that cannabis toxicity in dogs can be diagnosed with high specificity by veterinarians based only on history and clinical abnormalities.