Chronotherapy in veterinary medicine

Most clinical variables in animals follow biological rhythms which have a mathematical function defined by cosmic-climatic rhythms. Chronophysiology, chronopathology, chronopharmacology and chronotherapy have common elements but are frequently studied in isolation, thus making it difficult for a global understanding of clinical chronobiology as a unitary and well-defined discipline. The physiological effects of a drug depend not only on its molecular structure but also on the time-pattern of its administration. One of the main reasons for the importance of temporal patterns in drug activity is biological rhythm, and in particular that of the circadian period. These rhythms affect most physiological functions as well as drug metabolism, clearance, and dynamic processes that may alter drug availability and target cell responsiveness in relation to biological time. Chronotherapy studys the optimal level of drug effects and/or the minimizing of its toxicity by timing medications in relation to biological rhythms. This review focuses on medical chronobiology, which is much more technical since it only studies those aspects of clinical chronobiology having a health-care impact on daily practice.