Norethisterone (3-ketolynestrenol), the active metabolite of<unk> .<unk>  itself does not bind to the progesterone receptor and is inactive as a progestogen. It is a prodrug, and upon oral administration, is rapidly and almost completely converted into norethisterone, a potent progestogen, in the liver during first-pass metabolism. No other metabolites besides norethisterone are formed from<unk> . As such, its pharmacological activity is essentially identical to that of norethisterone. The conversion of<unk>  into norethisterone is catalyzed by CYP2C9 (28.0%), CYP2C19 (49.8%), and CYP3A4 (20.4%), while other cytochrome P450 enzymes are each responsible for no more than 1.0% of the total conversion. It appears that<unk>  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.<unk>  and its metabolites are predominantly excreted in urine, less in feces, active metabolite norethisterone elimination half-life being 16 or 17 hours. The pharmacokinetics of<unk>  have been reviewed.
Lynestrenol
Allylestrenol
Ethylestrenol
Norethandrolone
Androstanolone
Norethisterone
Nandrolone
Androstanolone valerate