Drug-supplement interaction (DSI)

Drug-supplement interaction (DSI) refers to the pharmacological phenomenon where a dietary supplement—such as a vitamin, mineral, or herb—alters the efficacy or safety of a pharmaceutical medication (NIH NCCIH, 2023). Unlike a specific biological receptor or enzyme, DSI is a complex event typically involving the modulation of metabolic pathways, most notably the Cytochrome P450 enzyme system, or drug transporters like P-glycoprotein (StatPearls, 2023). For example, St. John's Wort is a well-documented inducer of CYP3A4, which can lead to the rapid metabolism and subsequent failure of drugs like oral contraceptives or immunosuppressants (FDA, 2017; PubMed, 2022). Conversely, pharmacodynamic interactions can occur when supplements like Vitamin K directly antagonize the mechanism of drugs like Warfarin, or when Ginkgo biloba provides additive antiplatelet effects, increasing bleeding risks (NIH, 2021). Because many patients do not disclose supplement use to healthcare providers, these interactions represent a significant challenge for clinical safety and therapeutic monitoring.

Other names

Drug-herb interactionHerbal-drug interactionDrug-nutrient interactionDrug-dietary supplement interactionPharmacokinetic interactionPharmacodynamic interaction

Drug-supplement interactions occur through pharmacokinetic mechanisms, such as the induction or inhibition of Cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp) transporters, or through pharmacodynamic mechanisms where the supplement has additive, synergistic, or antagonistic effects on the drug's therapeutic target.