The efficacy and safety of cannabidiol as adjunct treatment for drug‐resistant idiopathic epilepsy in 51 dogs: A double‐blinded crossover study

Abstract Background Approximately 30% of dogs with idiopathic epilepsy (IE) are drug‐resistant. Recent studies have suggested cannabidiol (CBD) may be an effective anticonvulsant in dogs with IE. Objective To evaluate the addition of CBD to antiseizure drugs (ASDs) on seizure frequency and to report adverse events in dogs with drug‐resistant IE. Animals Fifty‐one dogs. Dogs having at least 2 seizures per month while receiving at least 1 ASD were included in the trial. Methods Double‐blinded placebo‐controlled crossover study. The 5 mg/kg/day dosage met futility requirements after 12 dogs, and a dosage of 9 mg/kg/day was used in the next 39 dogs. Dogs were randomly assigned to receive CBD or placebo for 3 months, with a 1‐month washout period between oils. Total numbers of seizures and seizure days were recorded. Diagnostic testing was performed periodically throughout the trial. Results At the 9 mg/kg/day dose, the decrease in total seizure frequency was significant compared with placebo. A 24.1% decrease in seizure days occurred in dogs receiving CBD and a 5.8% increase occurred in dogs receiving placebo (P ≤ .05). No significant difference was found in the number of responders (≥50% decrease in total seizures or seizure days). Liver enzyme activities increased at both dosages. Decreased appetite and vomiting were more common in the CBD phase (P ≤ .05). Conclusions and Clinical Importance Cannabidiol decreased total seizures and seizure days compared to placebo when administered to dogs PO at 9 mg/kg/day. Liver enzymes should be monitored with administration of CBD in dogs.