Multinational comparative clinical trial of long-acting injectable contraceptives: norethisterone enanthate given in two dosage regimens and depot-medroxyprogesterone acetate. Final report.

Final results are presented from a two-year WHO multinational comparative trial of three regimens: depot-medroxyprogesterone acetate (DMPA) given at 90-day intervals, norethisterone enanthate (NET-EN) given at 60-day intervals for the entire study period (NET-EN (60-day)), and NET-EN given at 60-day intervals for six months and thereafter at 84-day intervals (NET-EN (84-day)). 1587 DMPA subjects were observed for 20,550 woman-months, 789 NET-EN (60-day) subjects were observed for 10,361 woman-months, and 796 NET-EN (84-day) subjects were observed for 10,331 woman-months. This clinical trial represents the largest clinical trial undertaken on injectable contraceptives. After two years, the pregnancy rate with NET-EN (84-day) was 1.4 (+/- 0.6 S.E.) per 100 women, as compared with the two-year rates of 0.4 (+/- 0.3 S.E.) per 100 women observed with DMPA and 0.4 (+/- 0.2 S.E.) with NET-EN (60-day). Both discontinuation rates for amenorrhea and the prevalence of amenorrhea lasting more than 90 days were significantly higher with DMPA than with either NET-EN regimen. Terminations for bleeding problems were similar with the three treatments, despite a better cyclic pattern for the first six months with the NET-EN regimens. The three treatments were comparable with respect to discontinuation rates for other medical or personal reasons, and for all reasons combined. For family planning programs, NET-EN (60-day) has the advantage of low pregnancy rates compared to NET-EN (84-day), and a schedule of administration that does not change. Both NET-EN regimens produce less amenorrhea than DMPA. However, the NET-EN (60-day) regimen has the logistic and economic disadvantage of requiring more frequent injections. All three injectable regimens compare favourably with oral contraceptives in terms of pregnancy and total continuation rates observed in clinical trial settings.