The metabolic clearance rate and urinary excretion of oral contraceptive drugs: II. Mestranol

Abstract

Mestranol, a synthetic estrogenic drug, was administered to seven normal females and the rate of disappearance of the drug and its metabolites from the plasma was followed. In addition, urine was collected over the 5 days following injection and analyzed for daily excretion rates and for types of conjugation of mestranol metabolites. The rate of clearance of mestranol from the plasma was rapid with an average metabolic clearance rate (MCR) of 1,247 L. per day. Following these initial determinations, subjects were placed on a commercial oral contraceptive preparation containing 80 μg of mestranol per day. Each subject completed six cycles of this drug preparation; after completion, the MCR and urinary excretion rate of the drug were redetermined. Statistical comparisons of the MCR and urinary excretion rates made before and again after the six cycles of the drug show that prolonged mestranol administration had no effect on the rate of clearance (MCR), the rate of urinary excretion, or the mode of conjugation of mestranol or its metabolites.