Pharmacokinetics of ethynyloestradiol in women from different populations

Abstract

The pharmacokinetics of a dose of 501I g eth:nyloestradiol administered orally was studied in fourteen centres. lbsorption lr'arsa pid and the highest serum concentrations of total ethynyloestradiol were found in .,ost subjects at 1 h and by $4 h concentrations were less than 250 p:/':.l. Calculation of the half-lives for absorption, distribution and elildnation showed wide variations between subjects, the half-life of elimination varying from 2.; h to more than n0 h. Bioavailability as mensured by the area under the serum ethynyloestradiol concentration-tiniec urve also showed more th.an a ten-fold variation. Intra-centre differences in the various parameters measured were as large as the inter-centre differerccs.