Expert Discusses Cannabinoid Adverse Effects | ASHP Midyear 2025

Clinical pharmacist and educator Mark Garofoli, PharmD, MBA, BCGP, CPE, director of experiential learning at West Virginia University, discusses what he calls one of pharmacy’s growing responsibilities—understanding and managing the adverse effects and drug interactions of cannabinoids. Although hundreds of cannabinoids exist, Garofoli notes that the conversation for most patients still revolves around cannabidiol (CBD) and tetrahydrocannabinol (THC)—and that’s where the risks can become both subtle and serious.

On the surface, CBD may seem relatively benign, associated with familiar complaints such as nausea, vomiting, or diarrhea. THC, however, brings a more complex profile, with psychoactive and central nervous system effects that range from sedation and euphoria to, in some cases, acute psychosis—particularly with today’s high‑potency products. Garofoli points out that “this isn’t your grandma’s joint anymore,” and modern formulations often deliver far higher doses than in decades past, mirroring the historical shift in alcohol potency around Prohibition.

Compounding the challenge, many cannabinoid products are not prescription medications, and quality, potency, and labeling accuracy can vary widely. For pharmacists, the concern goes beyond enzymes like CYP450 to include high protein binding and clinically meaningful interactions with drugs such as warfarin, levothyroxine, and valproic acid—where even small changes can have outsized consequences, from destabilized seizure control to bleeding risk.

Garofoli underscores the heightened dangers for older adults on sedative medications and adolescents with developing brains or existing mental health conditions. He lays out what pharmacists need to know now, as cannabinoids move from the fringes into everyday practice.

"Just like there's a lot of other drug-drug interactions that may or may not have clinical significance," Garofoli said. "What we really want to talk about is the the cannabinoid drug-drug interactions that have clinical significance."

READ MORE: ASHP Midyear Clinical Meeting and Exhibition

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