Which supplement used for anxiety and depression is known for drug interaction potential?

• A. Garlic
• B. St. John's Wort
• C. Melatonin
• D. Black cohosh

Answer: (B)

Herbal agents used for mood can affect how many medicines work, especially when they alter drug metabolism. St. John’s Wort is the standout because it strongly induces liver enzymes that metabolize drugs, notably the cytochrome P450 system (especially CYP3A4) and P-glycoprotein. This means it can lower the blood levels—and therefore the effectiveness—of a wide range of medications, including oral contraceptives, warfarin, certain HIV medications, immunosuppressants, and some statins. It also raises serotonin levels, so combining it with other serotonergic antidepressants (like SSRIs or SNRIs) can risk serotonin syndrome. While garlic can interact with anticoagulants and melatonin serves mainly as a sleep aid, St. John’s Wort is the supplement most notorious for broad drug interaction potential, making it the best answer for this question.