Assessing potential herb-drug interactions: A clinical decision-making guideline to mitigate patient risk

Abstract

Complementary and Alternative (CAM) therapy use has been and continues to be prevalent in cancer patients, some of whom are taking herbal supplements. Studies indicate that 20% to 77% of these patients do not disclose their CAM use to their physician. Herb-drug interactions pose a considerable risk to the oncology patient population. The potential impact of any given herbal supplement on cytochrome isoenzymes, P-glycoprotein, UDP-Glucuronosyltransferase (UGT) enzymes, and other drug metabolism pathways needs to be evaluated to establish the risk of interactions with each medication that a cancer patient is taking. A review of the available literature reveals a varying array of human volunteer studies, case reports, in vitro and in vivo studies, often with contradictory results. Individual herbal products can greatly differ in the composition of their constituents, bioavailability, and thus interaction risk. A simplified clinical decision making guideline was developed to assist in easing the burden for physicians when faced with the question of whether a patient can safely take a particular herbal product. The guideline provides different scenarios with recommendations on how to approach each situation, as well as, recommendations for evidence-based non-herbal options to actively engage patients in their symptoms, while avoiding potentially deleterious interactions. Open dialogue about whether or not herbal supplements are appropriate, given the phase of treatment the patient is currently in, and having other options to suggest as alternatives may improve patient disclosure of herbal supplement use and compliance with their physician’s recommendations to discontinue supplements when necessary.