Medicinal plants: pharmacopoeial prescriptions.

Medicinal plants still account for 25% of medical prescriptions in developed countries and for more than 80% in developing countries. Vegetable raw materials available in the commercial market frequently do not comply with the requirements of constant activity, efficacy and quality. There is a need for more strict specifications of vegetable drugs and the pharmacopoeial prescriptions usually provide these specifications. The characteristics of pharmacopoeial prescriptions are discussed in view of most common problems in drug quality.