ABSTRACT
BACKGROUND: Patient harm resulting from drug interactions between conventional and traditional or complementary medicines (CM) are avoidable. OBJECTIVE: To provide a clinical overview of a selection of CM interactions with drugs commonly used in Australian general practice or in the management of COVID-19. DISCUSSION: Many herb constituents are substrates for cytochrome P450 enzymes, and inducers and/or inhibitors of transporters such as P-glycoprotein. Hypericum perforatum (St John's Wort), Hydrastis canadensis (golden seal), Ginkgo biloba (ginkgo) and Allium sativum (garlic) are reported to interact with many drugs. Simultaneous administration of certain anti-viral drugs with zinc compounds and several herbs should also be avoided. Preventing and identifying unwanted CM-drug interactions in primary care requires vigilance, access to CM-drug interaction checkers and excellent communication skills. Potential risks from interactions should be balanced against the potential benefits of continuing the drug and/or CM and involve shared decision making.