PXR as a mediator of herb-drug interaction

Abstract

Medicinal herbs have been a part of human medicine for thousands of years. The herb-drug interaction is an extension of drug-drug interaction, in which the consumptions of herbs cause alterations in the metabolism of drugs the patients happen to take at the same time. The pregnane X receptor (PXR) has been established as one of the most important transcriptional factors that regulate the expression of phase I enzymes, phase II enzymes, and drug transporters in the xenobiotic responses. Since its initial discovery, PXR has been implicated in multiple herb-drug interactions that can lead to alterations of the drug's pharmacokinetic properties and cause fluctuating therapeutic efficacies, possibly leading to complications. Regions of the world that heavily incorporate herbalism into their primary health care and people turning to alternative medicines as a personal choice could be at risk for adverse reactions or unintended results from these interactions. This article is intended to highlight our understanding of the PXR-mediated herb-drug interactions.

Keywords: Drug metabolism; Herb–drug interaction; PXR; St. John's Wort; Xenobiotics.

Fig. 1

Summary of the effect of Wu Wei Zi on drug metabolism. The overall net effect of an herb–drug interaction depends on the proportion of induction and inhibition triggered by constitutive phytochemicals contained in the herb. Phytochemical contents of herbs are generally susceptible to great variability in nature.