A review of "once-a-month" combined injectable contraceptives.

Abstract

The once-a-month combined progestogen and estrogen injectables were developed to overcome menstrual irregularity, a major reason for discontinuation of progestogen-only contraceptives. About 2 million women have already used the combined once-a-month injectables, particularly in Latin America and China. The currently available once-a-month combined injectable contraceptives are Chinese Injectable No. 1 (17 alpha-hydroxyprogesterone caproate, estradiol valerate), another formulation marketed under various brand names in Latin America (dihydroxyprogesterone acetophenide, estradiol enanthate), Cyclofem (medroxyprogesterone acetate [MPA], estradiol cypionate), Mesigyna (norethisterone enanthate, estradiol valerate), and Mego-E (megestrol acetate, 17 beta-estradiol). Cyclofem and Mesigyna are very effective at preventing pregnancy (1-year rate, 99.8-99.6%). The rate for the dihydroxyprogesterone acetophenide/estradiol enanthate formulation is 100%, while that for Chinese Injectable No. 1 is 94%. Even though menstrual disturbances occur less often in once-a-month injectable users, they are the leading medical reason for discontinuation. At 1 year of use, about 70% of Cyclofem and Mesigyna users have regular bleeding patterns compared to 8% of Depo-Provera users. None of the Cyclofem and Mesigyna studies have found them to induce any adverse or clinically relevant metabolic changes. Once-a-month combined estrogen and progestogen injectables do not cause any significant delay in return to ovulation, but researchers should collect more data on conception rates for women who discontinue for planned pregnancy and those who discontinue for bleeding disorders and amenorrhea. Research into service delivery of these injectables is needed to assess managerial requirements or adaptations that would be required should there be more wide scale introduction of a contraceptive into both public and private sectors. Age, contraceptive history, learning about injectables and husbands' attitude, and knowing another user's satisfaction with the service appear to be important determinants of acceptability of once-a-month injectables.