Topical and systemic effects of hydrocortisone 17-butyrate

In a series of hydrocortisone 17-esters, hydrocortisone 17-butyrate (HC-17B) has almost optimal lipophilicity resulting in a topical effect comparable to that of the fluorinated corticosteroids as measured in the McKenzie test on the human skin. In rats its systemic effects are weak, being in the order of those of hydrocortisone. In man systemic effects have been demonstrated, but no exact comparative. In man systemic effects have been demonstrated, but no exact comparative data are available. Important FACTORS controlling the intensity of systemic effects are: rate of liberation into plasma from the depot in the horny LAYER, RATE of metabolic degradation, and rate of plasma clearance. In rats the main factor seems to be rapid clearance from plasma (t 1/2 = 0.5h) by selective concentration in the liver and, to a lesser extent, in the kidneys. Rapid hydrolysis by esterases in plasma and liver plays an additional role. In man hydrolysis by esterases appears to be rather slow; the rate of clearance from plasma is still unknown, whereas the absorption from the intact skin into the blood seems to be very slow (t 1/2 = 25 h).