Circadian rhythms and clinical pharmacology

Almost all physiological functions in animal and man including vital signs display significant daily variations. The existence of internal clock(s) triggering circadian rhythms is now well established. In man, also the onset of certain diseases such as asthma attacks, coronary infarction, angina pectoris and peptic ulcers is not randomly distributed over 24 hours of a day. These rhythmic changes may have implications for drug therapy: In man more than 60 different drugs were shown to exhibit pronounced daily variations in their pharmacokinetics and/or in their effects or side effects. This data demonstrate that the time of day has to be taken into account as an additional parameter influencing the pharmacokinetics, the efficacy and the therapeutic range of drug therapy.