Combined injectable birth control

Combined injectable contraceptives (CICs) are a form of hormonal birth control for women. They consist of monthly injections of combined formulations containing an estrogen and a progestin to prevent pregnancy. CICs are different from progestogen-only injectable contraceptives (POICs), such as depot medroxyprogesterone acetate (DMPA; brand names Depo-Provera, Depo-SubQ Provera 104) and norethisterone enantate (NETE; brand name Noristerat), which are not combined with an estrogen and are given once every two to three months instead of once a month. Hormonal contraception works primarily by preventing ovulation, but it may also thicken the cervical mucus inhibiting sperm penetration. Hormonal contraceptives also have effects on the endometrium, that theoretically could affect implantation. CICs are administered by intramuscular injection into the deltoid, gluteus maximus, or anterior thigh. They are ideally administered every 28 to 30 days, though they have been demonstrated to be effective up to 33 days. Some CICs have been said to be used by transgender women as a means of feminizing hormone therapy as well. A variety of different CICs, generally containing a short-acting natural estradiol ester and a long-acting progestin ester, are available for clinical use. Estrogens that are used include estradiol valerate, estradiol cypionate, estradiol enantate, estradiol benzoate butyrate, and estradiol, while progestins that are used include norethisterone enantate, medroxyprogesterone acetate, algestone acetophenide (dihydroxyprogesterone acetophenide), hydroxyprogesterone caproate, and megestrol acetate. Estradiol benzoate has a duration that is too short for once-monthly CICs, and is not used in them. Conversely, estradiol enantate is said to have a duration that is too long for once-monthly CICs, but is nonetheless used in them. Side effects of CICs, besides menstrual bleeding changes, are minimal. The most prominent side effects of CICs are menstrual irregularities during the first 3 to 6 months of use.