 It appears that lynestrenol first undergoes hydroxylation of the C3 position, forming etynodiol as an intermediate, followed by oxygenation of the hydroxyl group to form norethisterone.The peak blood levels are reached within 2 to 4 hours after oral administration, 97% of the administered dose being bound to plasma proteins.Lynestrenol and its metabolites are predominantly excreted in urine, less in feces, active metabolite norethisterone elimination half-life being 16 or 17 hours.