Transporter modulation by Chinese herbal medicines and its mediated pharmacokinetic herb-drug interactions

The increasing use of Chinese herbal medicines (CHMs) as complementary therapy and dietary supplement has been greatly raising the concerns about potential herb-drug interactions (HDIs). HDIs may cause the augmented or antagonized effects of prescription drugs, resulting in unexpected clinical outcomes. Therefore, it is of significance to identify or predict potential HDIs, and to delineate the underlying mechanisms. Drug transporters play key roles in transmembrane passage of a large number of drugs, affecting their absorption, distribution and elimination. Modulation of drug transporters has been recognized as one of the main causes of HDIs. In the last decade, a growing number of Chinese medicinal herbs and their derived phytochemicals have been identified to have modulatory effect toward transporter proteins, leading to pharmacokinetic HDIs when concomitantly used with conventional drugs. Some of these transporter-mediated interactions have already shown clinical significance. This review article focuses on two major transporter superfamilies, the solute carrier (SLC) and the ATP-binding cassette (ABC) transporters, to provide the recent advanced knowledge on CHMs and their inherent phytochemicals that interact with these transporters, and their induced pharmacokinetic HDIs from both preclinical and clinical aspects. In addition, the challenges and strategy for studying HDIs are also discussed.