Multi national comparative clinical evaluation of 2 long acting injectable contraceptive steroids norethisterone enanthate and medroxy progesterone acetate
Benagiano, G.; Diczfalusy, E.; Goldzieher, J.W.; Gray, R.
Contraception 15(5): 513-534
1977
ISSN/ISBN: 0010-7824 Document Number: 439696
The use-effectiveness of 200 mg of norethisterone enanthate (NET-OEN) and of 150 mg of depot medroxyprogesterone acetate (DMPA) given every 12 wk .+-. 5 days was investigated in a randomized 10-center study involving 832 and 846 subjects, respectively. The study was planned to last 2 yr, but was terminated after approximately 1 yr because the pregnancy rate with NET-OEN exceeded the previously specificed allowable maximum. The cumulative 12 mo. gross pregnancy rate per 100 woman-yr was 3.6 .+-. 0.7 (SE) for NET-OEN and 0.7 .+-. 0.4 for DMPA. This difference is statistically significant. Two of the 10 centers contributed 54% of all pregnancies in the NET-OEN group. Of all conceptions with NET-OEN, 75% were estimated to have occurred during the 1st injection period, mostly in the last 4 wk of this interval. The high incidence of pregnancies at this particular time is statistically significant. The mean admission body weight of NET-OEN users who became pregnant was significantly lower than that of those who did not. There was no such difference among subjects treated with DMPA. The gross cumulative discontinuation rate for all medical reasons at 12 mo. was 16.9 .+-. 1.4/100 woman-yr for NET-OEN and 23.4 .+-. 1.7 for DMPA. This difference is statistically significant. The discontinuation rate for medical reasons in 1 center was significantly higher than in all other participating centers. This was chiefly attributable to menstrual abnormalities. The 12 mo. gross cumulative discontinuation rate for bleeding irregularities was 10.3/100 woman-yr for NET-OEN and 9.3 for DMPA, an insignificant difference. The 12 mo. gross cumulative discontinuation rate for amenorrhea was 1.8/100 woman-yr for NET-OEN and 11.5 for DMPA. This difference is statistically significant. After excluding from the calculations the center with atypically high results, the discontinuation rate for amenorrhea is markedly reduced but the difference between drugs is still significant. The discontinuation rate for non-medical reasons at 12 mo. was 9.5/100 woman-yr for NET-OEN and 7.7 for DMPA. This difference is not significant. On the average, approximately 6% of the subjects on both compounds were lost to follow-up.