Circadian variations in the effects of cardiovascular active drugs

It is now well established that all functions of the cardiovascular system display significant circadian variations (for review see [13–15]). Actually, biological rhythms in heart rate and blood pressure were described at the end of the 18th and the beginning of the 19th centuries. Falconer in 1797 described periodicities in pulse rate and mentioned that “the pulse, even in the state of perfect health, varies considerably at different times of day” [8]. Similarly, in 1801, Autenrieth described in his “Handbuch der empirischen menschlichen Physiologie” that the pulse was slower in the morning than in the evening and that daily changes occurred also in body temperature [4]. A daily variability in blood pressure was reported by Zadek in 1881 [35] and by Hill in 1898 [10]. Following these early reports, numerous more sophisticated studies have provided additional convincing evidence for circadian rhythms in heart rate and in systolic and diastolic blood pressure, both in healthy subjects and in patients suffering from cardiovascular diseases (for review see [13–17]).