VetMedCannabidiol oil as add-on therapy in canine idiopathic epilepsy — MAYBE (weak evidence)
In dogs with drug-resistant idiopathic epilepsy, does cannabidiol vs placebo, added to standard antiseizure drugs, reduce seizure frequency?
Shelf #292 · gate-verified and displayed under the developer's blinded-trial rule
MAYBE (weak evidence): In the one randomised blinded controlled trial, dogs receiving cannabidiol oil (2.5 mg/kg twice daily for 12 weeks) on top of conventional antiepileptic treatment had a significant median 33% reduction in seizure frequency compared with placebo — but only 9 CBD and 7 placebo dogs were included in the analysis, and the proportion of dogs considered responders (≥50% decrease in seizure activity) was similar between groups (McGrath 2019). A significant frequency change without a responder advantage, in 16 analysed dogs, is weak evidence, and this shelf is calibrated to exactly that. Drafted Nov 10, 2026 (VetMed build, topic #292); all figures from abstracts fetched and verified at drafting.
McGrath 2019: CBD group had a median 33% reduction in seizure frequency, but responder proportions were similar to placebo (16 dogs analysed)
Randomized blinded controlled clinical trial
Who: Dogs: 26 client-owned dogs with intractable idiopathic epilepsy, randomly assigned to cannabidiol (n = 12) or placebo (14); the CBD group received CBD-infused oil (2.5 mg/kg PO) twice daily for 12 weeks in addition to existing antiepileptic treatments, and the placebo group received noninfused oil under the same conditions.
Result: Two dogs in the CBD group developed ataxia and were withdrawn. After other exclusions, 9 dogs in the CBD group and 7 in the placebo group were included in the analysis. Dogs in the CBD group had a significant (median change, 33%) reduction in seizure frequency, compared with the placebo group; however, the proportion of dogs considered responders to treatment (≥50% decrease in seizure activity) was similar between groups. Plasma CBD concentrations were correlated with reduction in seizure frequency. Dogs in the CBD group had a significant increase in serum alkaline phosphatase activity; no adverse behavioral effects were reported by owners.
Watch out: Very small analysed sample (9 vs 7), a responder endpoint that did not separate from placebo, two ataxia withdrawals on CBD, and a significant alkaline phosphatase rise. The record's own conclusion is that additional research is warranted on whether a higher dosage would be effective — this card does not upgrade beyond that.
McGrath S, Bartner LR, Rao S et al. Randomized blinded controlled clinical trial to assess the effect of oral cannabidiol administration in addition to conventional antiepileptic treatment on seizure frequency in dogs with intractable idiopathic epilepsy. J Am Vet Med Assoc. 2019 Jun 1;254(11):1301-1308. PMID: 31067185. Registry ID: none in the record. MeSH: Animals · Anticonvulsants · Cannabidiol · Dog Diseases · Dogs · Drug Therapy, Combination · Epilepsy · Seizures
Synthesis: a signal on frequency, no signal on responders — weak evidence only
Synthesis
Who: Synthesis of the card above: McGrath 2019 (randomized blinded controlled trial, 26 dogs enrolled, 16 analysed). Single-trial shelf, stated on its face.
Result: The trial shows a statistically significant median reduction in seizure frequency on CBD alongside a responder proportion similar to placebo. Those two findings together, in this sample size, support no more than MAYBE (weak evidence) for an add-on effect at 2.5 mg/kg twice daily, with a liver-enzyme signal (alkaline phosphatase) to monitor.
Watch out: Commercial CBD products vary widely in content; the trial used a specific CBD-infused oil at a stated dose, and its result does not transfer to uncharacterised products.
Synthesis of McGrath S et al. PMID: 31067185. Registry ID as on the individual card.
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