The role of progestins in treating the pain of endometriosis

Progestins, synthetic progestational agents, have been used in the management of symptomatic endometriosis both as primary therapy and as an adjunct to surgical resection. A variety of oral agents have been employed in this regard with investigators demonstrating differing degrees of benefit. Unfortunately, due to the lack of large-scale, appropriately controlled, randomized trials, or dose-ranging studies, no single agent can be demonstrated to be truly efficacious. The lack of a standardized instrument to evaluate painful symptoms makes comparative analysis more difficult. Injectable administration of long-acting depot medroxyprogesterone acetate preparations intramuscularly or subcutaneously has been investigated in three randomized trials. The lower dose subcutaneous injection holds promise with an apparent reduction in side effects. Issues of reversible bone mineral density loss, breakthrough bleeding, and return of menses have not been completely resolved. Selective progesterone receptor modulators represent an intriguing alternative. These orally administered agents have been shown in preliminary investigations to be not only efficacious in reducing symptoms but also associated with minimal side effects. Further investigation of these agents is clearly required.