St. John's Wort & Multivitamins: Potential Interactions & Safety

Interaction Overview

St. John’s wort (Hypericum perforatum) is a potent inducer of cytochrome P450 enzymes (especially CYP3A4, CYP2C9) and P-glycoprotein efflux transporter. This accelerates the metabolism and reduces the bioavailability of many drugs—and potentially some vitamin/mineral components.

Specific Concerns with Multivitamins

• Folic acid: St. John’s wort may reduce folate levels; combined with methotrexate or sulfasalazine, increases toxicity risk.
• Vitamin K: Induction of vitamin K metabolism could theoretically affect anticoagulation stability in warfarin users taking multivitamins.
• B vitamins: Limited data; possible enhanced clearance of B12, B6.
• Fat-soluble vitamins (A, D, E, K): P-gp induction may reduce absorption.
• Minerals: No direct evidence, but altered gut motility could affect mineral uptake.

Clinical Recommendation

Avoid concurrent use. If St. John’s wort is indicated (mild-moderate depression), separate from multivitamin by at least 4–6 hours and monitor for reduced efficacy of either. Better: discuss with prescribing clinician; consider alternative antidepressant with less interaction potential.

Broader Interaction Profile

St. John’s wort significantly reduces levels of: oral contraceptives, antiretrovirals, immunosuppressants (cyclosporine, tacrolimus), warfarin, digoxin, theophylline, certain chemotherapeutics, and many others. Always disclose herbal use to all healthcare providers.