Herb-drug interactions: focus on pharmacokinetics.
Recent literature regarding drug-drug, herb-drug, and food-drug interactions must not be ignored; nor can they always be taken at face value. Studies have shown that St. John's wort (SJW) (Hypericum perforatum) can reduce plasma levels of indinavir, cyclosporin, digoxin, and possibly other drugs as well. Current knowledge regarding the metabolism of these medications suggests that the cytochrome P450 (CYP) drug metabolizing enzyme systems cannot account for all these effects. It has been reported that the P-glycoprotein (Pgp) transmembrane pump is also induced by SJW. Medications that are substrates of both CYP 3A4 and Pgp are of particular concern and may pose special interaction risks when combined with certain foods or botanical products such as SJW.
Cott
J M
JM
PsychoFarmacology Consulting Services, College Park, MD, USA. alkaloid@jerrycott.com