A rough 24-hour cycle driven endogenously in biochemical, physiological or behavioral processes is called circadian rhythm. Chronobiology is the study of biological temporal rhythms. For decades, we know that the biological rhythm and the drug metabolism are also affected from daylight and chronopharmacology became recognized by scientists in the early 1970s. Its lateral branch chronocopharmacokinetics is the study of rhythmic, predictable-in-time differences in the pharmacokinetics of drugs. Chronopharmacokinetic studies are performed at every step of the biotransformation i.e., absorption, distribution, metabolism and excretion. Feeding schedules, sex and phenotype must be taken into consideration while applying pharmacotherapy to increase the efficiency and to decrease side effects. The impact of drugs on circadian rhythm should be not neglected. On the other hand, new special drug delivery systems can be used to synchronize drug concentrations according to circadian rhythms. "Chronopharmaceuticals" can identify the proper dosing time and this amelioration will lead to improved progress and diffusion of pharmacotherapy. Chronopharmaceuticals coupled with nanotechnology could be the future of drug delivery systems, and lead to safer and more efficient disease therapy in the future. In this review, we will discuss the pharmacokinetic effects of circadian rhythm and its toxicological outcomes. Besides, we will try to give some practical points for clinical pharmacist/pharmacy practitioners, concerning chronopharmacokinetics.
Keywords: Absorption; chronocokinetics; chronopharmacology; circadian rhythm; distribution; excretion; metabolism.