[Consideration of biorhythms in systemic dermatotherapy with corticosteroids]

Rhythmic, in particular circadian, variations of body functions can be found in, or at least supposed for, almost all functions of the skin. The periodicity of physiological properties, some of which occur phase shifted to each other, represents the main reason for circadian differences of both the bioavailability and susceptibility to equal doses of drugs given at different day times. With regard to the well known circadian rhythm of ACTH and cortisol secretion, which can be suppressed by high dose administration of corticoids, every systemic corticoid treatment should, as a rule, be restricted to the morning hours, i.e. during the acrophase of endogenous cortisol secretion. Since after systemic or even topic corticoid therapy the rhythm of ACTH-cortisol feedback system may normalize with marked delay, skin reactivity tests as well as immunodiagnostic in vitro measures should be done just after appropriate poststeroid time lapse to avoid erroneous results. Some alteration of the circadian cortisol rhythm without foregoing corticoid treatment has also been found in cases of generalized atopic dermatitis as well as progressive systemic sclerosis of acrosclerotic type.