Drug-herb interaction: effect of St John's wort on bioavailability and metabolism of procainamide in mice.

Context: St John's wort induces the activity of the cytochrome P450 enzyme system causing treatment failure because of increased metabolism of many drugs. Procainamide is metabolized by a different pathway to N-acetyl procainamide.

Objective: To study St John's wort-procainamide interaction using a mouse (Swiss Webster) model.