Two Combined Monthly Injectables Prove Highly Effective in Chinese Trials

Abstract

In a trial involving women from 15 clinics in Chinas Shanghai Sichuan and Zhejiang provinces the effectiveness of two of three injectable contraceptive regimens was confirmed. Tested were Cyclofem (25 mg of medroxyprogesterone acetate and 5 mg of estradiol cypionate) Mesigyna (50 mg of norethisterone enanthate and 5 mg of estradiol valerate) and Injectable Number 1 (250 mg of hydroxyprogesterone caproate and 5 mg of estradiol valerate). The participants were women 18-35 years of age with regular menstrual cycles who were not pregnant or lactating and not taking medications known to affect the cardiovascular or hepatic systems. At the time of first injection women were given a physical examination and a menstrual diary; follow-up was monthly over a one-year period. Initial results indicated Injectable Number 1 manufactured and used only in China was significantly less effective in preventing pregnancy than the other two formulations. Thus the study was modified to compare 1724 woman-years of Mesigyna use with 1647 woman-years of Cyclofem use. The one-year discontinuation rate was 19% in the former and 26% in the latter group. There were six pregnancies among Mesigyna users (0.3/100 woman-years) and three among Cyclofem users (0.1/100 woman-years). The one-year discontinuation rate related to bleeding irregularities or amenorrhea was significantly higher among Cyclofem users (12.7/100 woman-years) than Mesigyna users (7.9/100 woman-years). However discontinuation for other medical reasons (primarily weight gain and breast tenderness) was comparable: 3.4/100 and 3.6/100 woman-years respectively. At the first monthly follow-up visit 16% of Cyclofem users and 12% of Mesigyna users complained of bleeding irregularities; by the 12-month visit these percentages had dropped to 3% and 1% respectively. Overall the discontinuation rates for bleeding irregularities compare favorably to those reported for progestogen-only injectables.