[Herbal medicines: when to use or not to use?].

Herbal medicines are popular. It is frequently assumed that they are effective and safe. Sound knowledge of existing, or lacking, data on the efficacy and safety is required for advice and for the decision whether or not to use a particular herbal drug. Cochrane reviews are available for some herbal remedies. Most of them indicate either insufficient knowledge or weak or lacking efficacy. Numerous studies on interactions, some of which are clinically significant, for St. John's wort with conventional drugs are available. Overall, although knowledge about herbal drugs has grown in recent years, it is generally still unsatisfactory. The active recommendation to use an herbal drug is usually not advisable. However, a patient's request for a licensed herbal drug may be acceptable if there is no conventional concomitant comedication that is known or expected to interact, no contra-indication, and no other (conventional) treatment with better, or better known, benefit-risk ratio.