Herb-drug interactions: an evidence based approach.

The increasing use of herbal medicinal products (HMPs) in the community where people are also receiving prescription medicines suggests that adverse herb-drug interactions may be of significant public health consequence. The evidence available to guide practitioners in decision making is complex and consists of a range of sources including adverse event database entries, spontaneous or case reports, in vivo and in vitro drug metabolism studies, and in vivo drug interaction studies in healthy subjects and patients. In the absence of further rigorous studies to assess the clinical significance of herb-drug interactions, an evidence-based appraisal of the current literature is essential to guide practitioners involved in patient care.