PHARMACOKINETICS OF ORALLY-ADMINISTERED NORETHISTERONE ENANTHATE IN RABBIT, MONKEY, AND WOMEN

Norethisterone enanthate (NET-En), an established intramuscular long-a cting contraceptive agent, has previously been shown to be effective i n inhibiting fertility in two rodent species even 4 days after oral in gestion. Pharmacokinetics of NET and NET-En were studied after oral an d intramuscular doses in two animal species and a few women. The resul ts suggest that the NET-En was absorbed within a day in all the specie s after oral dose. The estimates of relative bioavailability ranged fr om 23 to 51 % in rabbits, monkeys, and women. The elimination half-lif e was 5-10 days. The presence of the active component, NET, in the cir culation over the experimental period of 15 days suggests that NET-En could be useful as a long-acting oral pill. The suppression of progest erone levels during the luteal phase of menstrual cycle in women also supports this finding. (C) 1997 Elsevier Science Inc. All rights reser ved.