[Chronopharmacology and psychiatric treatment]

In order for a drug to act it must be present at the correct concentration in its sites of action... but also at the right time. It is now clearly established that the body which receives a drug is made up of a set of biological rhythms and that the effects, toxicity and kinetics of the drug depend on the time when it is administered, the concept of chronopharmacology. As in other areas, the activity and safety of drugs used for psychiatric treatment depend on their time of administration : chronopharmacological studies have, for example, shown the effects of some antidepressants (imipramine, chlorimipramine, clorgyline etc) on the rhythm period in animals. Variability associated with the time when psychotropic drugs such as the anti-psychotics, stimulates antidepressants and benzodiazepines for example are given has also been demonstrated. These chronopharmacological effects can be explained by temporal variations in the mechanism of action of the drug on receptors, or of its fate in the body (chronokinetics). Application of these concepts to the treatment of psychiatric diseases, many of which are associated with dysfunction of the biological clocks, has led to chronotherapeutic studies on, for example, clomipramine, haloperidol and imipramine intended to define a better dosing time for efficacy and/or safety.