Medical contraindications and issues for consideration in the use of once-a-month injectable contraceptives

A number of once-a-month injectable contraceptives have been studied over the last 30 years and at least three different formulations are currently in use worldwide. Each of these formulations contains an ester of the natural estrogen, estradiol, and a synthetic progestin. This is in contrast to the combined oral contraceptives which contain synthetic analogs of both estradiol and progesterone. This paper considers medical contraindications or precautions related to the use of once-a-month injectable formulations and suggests some considerations for their programmatic use, particularly in the developing world. Because once-a-month injectables contain both an estrogen and a progestin, the precautions related to their use are similar to those of combined oral contraceptives; however, since the estrogen component is a natural estrogen, administration is parenteral and the circulating levels reach peaks that are in the range of those of the normal preovulatory phase of the menstrual cycle, some of these precautions may be very conservative. Absolute contraindications to the use of monthly injectables are current or suspected pregnancy, and estrogen-responsive tumors of the breast or genital tract. Other factors have been termed precautions for use rather than absolute or relative contraindications. Primary precautions are conditions under which a woman should probably not use monthly injectables, but if she does, she should be monitored closely. These include current or individual history of cardiovascular disease, current liver disease or liver tumors, and over age 40 if a smoker. Secondary precautions to use are those which should be considered very carefully and balanced against the risks of not using the particular method. These include suspicion of breast or genital tract cancer until cancer is ruled out, unexplained abnormal vaginal bleeding, use of drugs which might affect metabolism and decrease effective levels of circulating steroids, breastfeeding, and having combinations of several risk factors for cardiovascular disease. These precautions are categorized as proposed, based on the fact that most women in the developing world face a risk from pregnancy that is probably far greater than the risks from any of the present formulations of steroidal contraceptives. A key consideration during programmatic use of monthly injectables is attention to compliance with follow-up schedules to minimize the risk of pregnancy. Because little information on monthly injectables is available that is directly related to these precautions, additional research studies will be required in order to reconsider whether some of the listed precautions are valid or others should be considered.