Injectable Progestogens: Officials debate but use increases
A report on the status of the injectable contraceptive agents, Depo-Provera (depot medroxyprogesterone acetate) and Norigest is presented. Depo-Provera is distributed in 64 countries, though it is not available in the U.S., the United Kingdom, and Japan. The drug is usually administered in single 150 mg injections every 3 months, and doses of 300-400 mg every 6 months have been studied. The contraceptive effect of Depo-Provera is primarily through its ability to inhibit ovulation. Norigest exerts its effect by altering the cervical mucus. The suppression of ovulation is most likely caused by action on the hypothalamus-pituitary axis, resulting in inhibition of the luteinizing hormone surge. Depo-Provera causes an atrophic endometrium, while Norigest has varying endometrial effects. The reported pregnancy rates for Depo-Provera are usually less than 1%, while those for Norigest are slightly higher. Most method failures occur either shortly after the 1st injection or at the end of an injection interval. Menstrual disorders have been the primary reason for discontinuation. The injectables can cuase shorter or longer cycles, increased or decreased menstrual flow, and spotting. Depo-Provera users experience increased amenorrhea with continued use, while normal cycles increasingly reappear in Norigest users. Cyclic estrogen therapy has been effective in treating excessive or irregular bleeding and amenorrhea. Long-acting estrogen injections have been administered in combination with Depo-Provera or Norigest, though the studies are limited in number. Weight gain of up to 9 pounds has been reported for users of Depo-Provera. Some researchers have found that Depo-Provera raises blood glucose levels, while others have reported it does not. No adverse effects have been reported for injectables on blood clotting, adrenal or liver function, blood pressure, lactation, and metabolic or endocrine functions. The continuation rate for Depo-Provera is reportedly higher than that for oral contraceptives. Generally, 60% of the acceptors will use the method for at least 1 year. Effective counseling on the menstrual alterations resulting from injectables can increase continuation of the method. The return of fertility in Depo-Provera users usually requires 13 months from the time of the last injection, while the afertile period in Norigest users is about 6 months from the time of the last injection. Instances of fetal masculinization as a result of Depo-Provera use have not occurred. The possibility that Depo-Provera can cause cervical carcinoma in situ has not been substantiated by the evidence; doubt about this possible association has prevented its approval as a contraceptive method in the U.S. Although Depo-Provera and Norigest have caused breast nodules in laboratory animals, there is no evidence to suggest that this effect would occur in human. Despite the advantages of injectables, family planning officials have been reluctant to permit its unrestricted use, primarily because it cannot be withdrawn guickly enough if problems arise and because the actual effect on fertility is not yet known. Nonetheless, the use of Depo-Provera has increased in recent years. The IPPF and the U.N. Fund for Population Activities currently supply the drug.