St John's Wort increases expression of P‐glycoprotein: Implications for drug interactions

Abstract

SJW increased expression and enhanced the drug efflux function of the multi drug transporter P-glycoprotein in PBMCs of healthy volunteers. This may represent a second mechanism for the drug-herb interactions seen in clinical practice and account for the discrepancies between in vitro and in vivo data. Since P-glycoprotein and CYP3A4 have distinct though overlapping substrates, patients receiving drugs, which are P-glycoprotein substrates should be warned against self-medication with SJW as clinically significant drug interactions may occur.