["Natural drugs": old myths and new markets]

In spite of its ambiguity, the use of the locution natural drug is spreading in the lay media and efforts are made to introduce it in more scientific contexts. Although it should only have the neutral meaning of indicating drugs obtained from plants, animals or minerals, attempts have been made to attribute to these drugs, particularly those of animal origin, mechanisms of action and pharmacological effects not shared by synthetic drugs. For instance, natural drugs are supposed to escape the hepatic microsomal metabolism, thus avoiding the production of toxic metabolites and minimizing chances of causing side effects. Unfortunately, these speculations are largely unproved and, although they may look as a progress in pharmacology, probably are nothing but relics of early stages of medical knowledge, when living matter was considered to give peculiar and metaphysical properties to its chemical components. A brief account of the history of these beliefs is given.