The objective of this study was to assess the frequency of clinically significant interactions caused by concurrent use of dietary supplements and prescription medication.

We conducted a cross-sectional, point-of-care survey and combined the findings with a review of patient medical records. Patients treated at Mayo Clinic (Rochester, Minn) in 6 different specialty clinics were surveyed for their use of dietary supplements. Concurrent use of prescription medications was obtained from patients’ medical records. We used the Lexi-Interact online medication and dietary supplement interaction analysis program to assess the potential clinical significance of each interaction.

We surveyed 1818 patients; 1795 responded (overall response rate of 98.7%) and 710 (39.6%) reported use of dietary supplements. In total, 107 interactions with potential clinical significance were identified. The 5 most common natural products with a potential for interaction (garlic, valerian, kava, ginkgo, and St John’s wort) accounted for 68% of the potential clinically significant interactions. The 4 most common classes of prescription medications with a potential for interaction (antithrombotic medications, sedatives, antidepressant agents, and antidiabetic agents) accounted for 94% of the potential clinically significant interactions. No patient was harmed seriously from any interaction.

A small number of prescription medications and dietary supplements accounted for most of the interactions. The actual potential for harm was low.