What clinical signs and treatment should I expect for a dog that ingested cannabis or a THC concentrate?

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The hallmark clinical signs of canine cannabis/THC intoxication are ataxia, urinary incontinence, lethargy, hyperesthesia, hypersalivation, and mydriasis, with onset typically within 1.25 hours of ingestion (range 0.5–12 hours). Most dogs develop signs within 4 hours of ingestion.7 Ataxia is the most frequently observed sign, reported in 35 of 38 dogs in one plasma-confirmed case series.3 Hyperesthesia was documented in 75.2% of dogs in the largest published case series.7 Cardiovascular abnormalities, when present, are more commonly tachycardia and hypertension rather than the bradycardia and hypotension traditionally expected — though bradycardia, hypotension, and hypothermia do occur and are dose-dependent.7 In severe cases, seizures, tremors, hyperthermia, vomiting, and hypotension can occur.4 Diagnosis is clinical — history combined with the characteristic sign cluster confirms the diagnosis with high specificity, and laboratory confirmation does not alter treatment decisions. Plasma cannabinoids were quantifiable in 37 of 38 dogs presenting with suspected intoxication based on history and physical examination alone.3 Of the clinical signs recorded, only abnormal reflexes correlated with plasma THC concentration at the time of sampling.3 Over-the-counter urine drug screens designed for humans measure THC-COOH and are not sensitive enough for canine urine due to low THC-COOH concentrations in dogs.4 Treatment is decontamination followed by supportive care — there is no specific antidote for cannabinoids. Supportive care is the established standard.4 Clinicians should monitor for and address CNS depression, urinary incontinence, cardiovascular abnormalities, and thermoregulatory dysfunction. Because cannabinoids are potent inhibitors of cytochrome P450 enzymes (particularly cannabidiol/CBD), any co-administered drugs should be reviewed for interactions, and hepatic enzyme monitoring is warranted with ongoing exposure.2 When cannabinoids are combined with calcium-c