[Recent data in chronopharmacokinetics].

Time of drug administration may be responsible among other factors for nonlinearity in pharmacokinetics. More than a hundred studies have reported on chronokinetics. Absorption, distribution, metabolism and elimination rate of a drug depend on temporal variations: drug absorption processes vary with time of day even in fasting conditions. Temporal changes in membrane permeability may be involved in temporal variations of distribution such as in protein binding. Circadian variations of the metabolism of a drug may also depend on circadian changes of metabolizing enzymes activities or on blood flow variations in the concerned organs. Finally the elimination rate of drugs depends on timing of administration according to renal blood flow, glomerular filtration and pH variations. Such chronokinetic studies are needed for a better understanding of nonlinearity of kinetics and may explain, in part at least, chronopharmacological data.