Drugs have always been both medicine and poison. Their function is cure but they can also kill; they have desired but also adverse effects. Drugs can be defined as technical objects which use is inserted within a set of representations, practices and social relationships. Acting as a mediator--and sometimes as an issue--in the relationship, medication and its use are far from the rational management of drugs as defined by public health authorities. The matter at stake can also be the legitimation of illness or pain. As a means of legitimation, psychotropic drugs raise specific questions as there is no objectivation of symptoms, be them mood changes or pain, aside from the patient's account.