Pharmacokinetic herb-drug interactions (part 2): drug interactions involving popular botanical dietary supplements and their clinical relevance.

In Part 2 of this review, a critical examination of the pertinent scientific literature is undertaken in order to assess the interaction risk that popular dietary supplements may pose when taken concomitantly with conventional medications. Botanicals most likely to produce clinically important herb-drug interactions are those whose phytochemicals act as mechanism-based inhibitors of cytochrome P450 enzyme activity (e.g., Hydrastis canadensis, Piper nigrum, Schisandra chinensis) or function as ligands for orphan nuclear receptors (e.g., Hypericum perforatum). In addition, several external factors unrelated to phytochemical pharmacology can augment the drug interaction potential of botanical supplements.