Drug-drug interaction

A drug-drug interaction occurs when one substance changes the concentration, effect, or safety of another substance taken at the same time.

Interactions fall into two broad types. Pharmacokinetic interactions change how much of a drug reaches the blood, usually by affecting the enzymes or transporters that metabolize or move it. Pharmacodynamic interactions occur when two substances act on the same body system, so that effects such as sedation add together. Pharmacists screen for both using interaction databases, and prescribing information lists the combinations that have been studied.

Cannabidiol is metabolized by, and can inhibit, several cytochrome P450 enzymes, giving it the potential for pharmacokinetic interactions with many medications. The best-documented examples involve clobazam and valproate, both identified in clinical trials of prescription CBD. Additive drowsiness with sedating drugs or alcohol is a pharmacodynamic concern. Most combinations at retail-product amounts have not been formally studied, so anyone taking prescription medication is generally advised to discuss cannabinoid use with a pharmacist or prescriber.