gynecology and obstetrics
Progestin Contraceptive Injections
Introduction
Various contraceptive progestin injections are available worldwide. Depotmedroxyprogesteroneacetate (DMPA)is a long-acting injectable formulation ofmedroxyprogesteroneacetate in a crystalline suspension. With DMPA, pregnancy rates in the first year are 0.2% with perfect use and about 6% with typical use (ie, delays between injections). DMPA is available in two different formulations; it may be given as an IM (150 mg) or subcutaneous injection (104 mg) every 3 months. The injection site should not be massaged because doing so may increase the rate of absorption. Effective contraceptive hormonal serum levels are usually attained as early as 24 hours after injection and are maintained for at least 14 weeks although levels may be high enough to remain effective for up to 16 weeks. If the interval between injections is>16 weeks, a pregnancy test should be done before the next injection is given. DMPA may be started immediately (a quick-start protocol) if DMPA is given within the first 5 to 7 days of the menstrual cycle. If it is not started during this time frame, a backup contraceptive method should be used concurrently for 7 days. DMPA may also be given immediately after a spontaneous or induced abortion or immediately postpartum regardless of breastfeeding status. Noristerat (NET-EN), which is not available in the United States, is a long-acting injectable formulation of norethisterone enanthate in acastor oilbenzyl benzoate suspension. Pregnancy rates are the same as with DMPA. NET-EN may be given as an IM injection (200 mg) deep into the gluteal or deltoid muscles, typically every 8 weeks, but the interval can be extended to 12 weeks after the first 6 months of use. As with DMPA, the injection site should not be massaged. Effective contraceptive hormonal serum levels are usually attained within 72 hours. If the interval between injections is > 13 weeks, a pregnancy test should be done before the next injection is given. NET-EN may follow the same quick-start protocol as DMPA, with the same backup contraceptive protocols. And like DMPA, NET-EN may also be given immediately after a spontaneous or induced abortion or immediately postpartum, regardless of breastfeeding status. 