Is THC (Δ9-Tetrahydrocannabinol) safe for dogs and cats?

Dogs are significantly more sensitive to THC than humans due to a higher density of CB1 cannabinoid receptors in the cerebellum and brainstem, resulting in more pronounced neurological effects at equivalent doses. Exposure sources have dramatically increased with cannabis legalization: edibles (gummies, brownies, butter, chocolates), concentrated extracts (wax, shatter, oil — up to 90% THC), cannabis plant material, and secondhand smoke in enclosed spaces. Edibles are the most common cause of severe toxicosis in dogs — chocolate cannabis brownies combine THC and chocolate (theobromine) toxicity. The minimum dose producing clinical signs in dogs is approximately 3 mg/kg THC; clinical toxicosis is well-established at doses of 20–100 mg/kg and above (readily achievable from concentrated edibles). Clinical signs: ataxia (classic drunken gait), urinary incontinence, mydriasis, bradycardia, hypothermia, hypersalivation, vomiting, tremors, and in severe cases, coma. Most dogs recover within 12–72 hours with supportive care; fatalities are rare but reported with extreme exposures. ASPCA APCC cannabis calls have increased over 700% from 2009 to 2019 parallel to legalization. Treatment: activated charcoal (if recent ingestion and not ataxic), anti-nausea medications, IV fluids, temperature management. No specific antidote.

Cats are susceptible to THC toxicosis but are considerably less commonly exposed than dogs, reflecting their dietary selectivity (cats are less likely to consume cannabis edibles, plant material, or food residues). When cats are exposed — primarily via passive smoke inhalation in cannabis-using households, or ingestion of concentrated products — clinical signs are similar to those in dogs: ataxia, hypersalivation, dilated pupils, lethargy, and vocalization. Cats may be more sensitive per unit dose than dogs based on limited pharmacokinetic data. Secondhand cannabis smoke exposure in enclosed spaces over time may cause chronic low-level cannabinoid effects; this is an emerging area without definitive toxicological data. Treatment for acute THC toxicosis in cats follows the same supportive approach as in dogs. Veterinary clinics are increasingly seeing cat THC exposures in states with legal recreational cannabis.