Human metabolism and steroid contraceptives. Part 1.

Metabolic activation of mestranol and certain progestagens is necessary before combination with their specific receptors. This process is subject to inhibition by other drugs. It is suggested that it is preferable to use agents not requiring metabolic activation. Widespread variation of human metabolic parameters is induced by oral contraceptives. A dose related effect of synthetic oestrogens on the synthesis and release of liver-derived plasma proteins is a major cause of this variation. The changes induced may be modified by norgestrel but not by other available progestagens. Changes in various specific plasma proteins, carrier proteins, enzymes and coagulation factors are discussed.