Cannabidiol Drug Interactions: Why Liver and Co-Medication Monitoring Matter in Dogs

TL;DR

Two 2024-2026 reviews reinforce that cannabidiol is cleared hepatically and can engage cytochrome P450-mediated drug interactions, which matters when CBD is added to dogs already on antiseizure or other hepatically metabolized drugs.

What just dropped

• A comparative veterinary review of the endocannabinoid system and phytocannabinoids summarizes the pharmacokinetics, efficacy, and tolerability of cannabis derivatives — predominantly cannabidiol-containing products — across dogs, cats, horses, and other species of veterinary interest. Source: https://europepmc.org/articles/PMC11442603
• A 2026 clinical pharmacology review of cannabinoids and drug-drug pharmacokinetic interactions critically discusses how major cannabinoids, including cannabidiol, can alter the absorption, distribution, metabolism, and excretion of co-administered drugs, including medications used for epilepsy. Source: https://europepmc.org/articles/PMC13122281

Context

The veterinary review makes hepatic metabolism central to cannabidiol disposition in companion species, and a deep understanding of these pharmacokinetics is described as crucial for therapeutic use across the main species of veterinary interest. Building on that, the clinical pharmacology review catalogues the pharmacokinetic interaction risks of cannabinoids with drugs spanning neurology, psychiatry, and cardiometabolic disease, including antiseizure agents.

The practical signal for veterinary medicine is consistent with what the canine epilepsy trials show indirectly: cannabidiol use is associated with reproducible increases in liver enzyme activity, and concurrent hepatically cleared drugs warrant attention. The 2026 review is human-focused in its examples, so its species-specific applicability is limited; it is best used to frame the mechanism rather than to set veterinary thresholds.

What this changes in the cannabidiol evidence picture

For clinicians weighing a cannabidiol trial in a dog already on antiseizure drugs (see the cannabidiol evergreen at https://www.thevoyage.ai/forvets/knowledge/cannabidiol-canine-epilepsy), these reviews reinforce two practice points: monitor liver enzymes, and consider the potential for pharmacokinetic interaction with co-administered, hepatically metabolized medications. Neither review supports a specific dose adjustment in dogs, and any interaction management should be confirmed against a current formulary and the clinician's own judgment.

References

1. Di Salvo A, Chiaradia E, Sforna M, Della Rocca G. 2024. Endocannabinoid system and phytocannabinoids in the main species of veterinary interest: a comparative review. Vet Res Commun. https://europepmc.org/articles/PMC11442603
2. Papakyriakopoulou P, Valsami G, Ismailos G. 2026. Cannabinoids and drug-drug pharmacokinetic interactions: Deciphering the risks. Br J Clin Pharmacol. https://europepmc.org/articles/PMC13122281

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