[Drug addiction: definition and classification].

Basic aspects of drug abuse are discussed, from a semantic and physiopathologic point of view: drug definition; drug abuse and drug addiction; drug as a tool, that produces adverse or beneficial effects according to its use, rather than its intrinsic features. Simple and complicated drug-related problems are discussed in some depth, the former being associated with external factors, the latter with organic or mental disease. Practical implications of this concept are exposed. Similarities of drug abuse and suicide are underlined. It is concluded that ethical judgments and measures require an additional evaluation of these aspects, with particular reference to the medical component of drug abuse.