Abstract :
Chronobiology is the study of biological rhythms and underlying mechanisms. Medical chronobiology is the application of rhythms in medicine. Rhythms are endogenous in origin and paced by master clocks located in the brain and synchronized by environmental and societal time cues -- the light-dark and sleep-wake cycles. Prominent circadian ( 24h) rhythms is endocrine, hematologic and other variables influence the findings of diagnostic tests and the occurrence and treatment of disease. Angina, arthritis (rheumatoid), asthma, rhinitis and ulcer disease worsen during sleep; osteoarthritis worsens and hemorrhagic stroke occurs in the evening. These temporal patterns are due both to rhythms in critical functions plus differences in environmental stress over the 24h; elevated morning risk of myocardial infarct results from circadian rhythms of blood pressure, blood coagulation, coronary blood flow and ischemia, among others, coincident with the stress of morning activity/work. Chronotherapeutics is the formulation and scheduling of medications to account for rhythm-dependencies in drug kinetics or dynamics and the pathophysiology of disease processes. Alternate-day morning methylprednisolone tablet dosing was the first chronotherapy. Evening theophylline for nocturnal asthma, dinner-time H2-antagonists for ulcer disease and evening antilipemics for hypercholesterolemia are others. COERR verapamil (Searle), a chronotherapy of hypertension, delivers varying amounts of medication over the 24h to optimize blood pressure control especially in the morning and during the daytime when highest without inducing hypotension overnight and is protective of morning-time angina.
