Chronopharmacology: a new perspective in pharmacology.

Vital signs and several constituents of the serum and urine exhibit a circadian rhythm, and the same is true for the onset of several diseases. The rhythmic changes in the blood volume, functions of the liver and kidney, etc., have implications for drug availability, and the circadian changes should be taken into account in pharmacokinetic studies. These changes are the subject of chronopharmacokinetics. In addition to the circadian rhythm in changes in drug absorption, elimination and bioavailability, a rhythm of the intensity of drug effects and side-effects may also be observed: this is the domain of chronopharmacodynamics. Several examples demonstrate that chronopharmacokinetic and chronopharmacodynamic results support the view that the temporal organization of the organism is an important variable influencing the action of drugs.