Serum progesterone and norethisterone levels following injection of norethisterone enanthate in different sites and doses.

Serum progesterone (P) and norethisterone (NET) levels following injection of norethisterone enanthate (NETEN) were studied in 11 regularly menstruating women. In 6 subjects 200 mg NETEN was administered to the gluteal (IG) or deltoid (ID) region sequentially. The serum P levels remained anovulatory (less than 4 ng/mL) up to 12 weeks. Serum NET levels were similar whether injection was given IG or ID (paired t - test, NS). In 5 subjects given a 150-mg dose, serum P levels remained anovulatory up to 11 weeks. Serum NET levels declined faster than with the 200-mg dose, but the difference was not significant (Student's t - test, NS). Wide inter-subject variations were seen in both groups. NETEN therefore can effectively be administered in gluteal or deltoid regions. A lower dose of 150 mg may have contraceptive potential on an 8-week schedule.