Drug-Supplement Interaction

Drug-supplement interactions (DSIs) occur when a dietary supplement affects the absorption, metabolism, distribution, or excretion of a prescription or over-the-counter medication, or vice versa. Interactions can be pharmacokinetic (affecting drug levels — e.g., St. John's Wort inducing CYP3A4 and reducing blood thinner efficacy) or pharmacodynamic (additive or opposing effects — e.g., melatonin plus sedative medications causing excessive drowsiness). Common DSIs in sleep and hair supplement research include: iron binding to thyroid medication, melatonin potentiating anticoagulants, kava enhancing sedative effects, and high-dose vitamin E increasing bleeding risk with blood thinners. Disclosing all supplements to healthcare providers is essential for safe supplementation.