Depo-Provera is an injectable form of a progestin. It was approved by the FDA in 1992 for contraceptive use. Previously, it was approved for treating endometrial and renal cancers. Depo-Provera has a failure rate of only 1%. Each injection provides contraceptive protection for 14 weeks. It is injected every 3 months into a muscle in the buttocks or arm by a trained professional. The side effects are the same as those for Norplant and progestin-only pills. In addition, there may be irregular bleeding and spotting during the first months followed by periods of amenorrhea (no menstrual period). About 50% of the women who use Depo-Provera for 1 year or longer report amenorrhea. Other side effects, such as weight gain and others described for Norplant, may occur.