RESUMO
Many studies, both retrospective and prospective, have shown that there is a circadian variation in acute cardiovascular events with a peak during the morning and a trough during the night since the mid 1980s. In addition to the morning peak, a secondary less prominent peak has been observed in the late afternoon in many studies. This circadian variation may well be at least partly linked to the known physiological circadian rhythms. Because the duration of the therapeutic effect of many drugs taken at the conventional time will have reached subtherapeutic levels at the time of waking and commencing activity the following morning, timing of medication is discussed to improve the protection of the patients with cardiovascular disease in the morning waking hours.