Abstract
Physiological functions of cardiovascular system (CVS) are exhibiting circadian patterns regulated by complex system of endogenous factors. Preserving this rhythmicity is important for its normal function, whereas disturbing the synchronization with natural day–night cycle can increase the risk of cardiovascular damage. Cardiovascular pathophysiology also follows cyclic variation; time susceptibility and period with maximum risk associated with elevated blood pressure (BP) can be predicted. Given this rhythmic nature, significant changes in efficacy between morning and evening administration of the drug may occur; appropriate timing of pharmacological intervention in therapy of hypertension may affect the efficacy of the treatment.