A multicentred, two-year, phase III clinical trial of norethisterone enanthate 50 MG plus estradiol valerate 5 MG as a monthly injectable contraceptive

Abstract Norethisterone enanthate (NET-EN) 50 mg combined with estradiol valerate (EV) 5 mg was studied as a once-a-month injectable contraceptive with regard to effectiveness, cycle control, adverse events and acceptability. In eight Family Planning Centres from 5 Latin American countries, 652 fertile women were followed-up for a period of 24 months, providing a total of 10,689 woman-months of experience. Only 1 pregnancy occurred, in the first treated month a few days before the second injection (failure rate 0.11 per 100 woman-years). Under treatment, the first cycle was drastically shortened in most cases, but thereafter cycles tended to recover to pre-treatment patterns. There was a significant decrease of hypermenorrhea and dysmenorrheic cycles. Intracyclic bleeding and spotting appeared in 1.2% and 2.4%, respectively, and amenorrhea in 2.5% of cycles. Incidence of other adverse events was very low with the exception of weight gain of 2 Kg (28%). Continuation rate at 12 months was 64.7%. The cumulative discontinuation rate due to bleeding problems was 7.4% and 10.7% due to adverse events at 24 months.