Endometriosis - Medications

Mifepristone. Mifepristone (Mifeprex) is another antiprogestin that is effective for treating endometriosis. In one six-month study, mifepristone improved symptoms and reduced endometrial implants without causing menopausal side effects. Long-term use, however, may cause changes in the uterine tissue and cell proliferation.

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Investigative Drugs

GnRH Antagonists. GnRH antagonists include ganirelix (Antagon) and cetrorelix (Cetrotide). These are newer agents differ from GnRH agonists in that they have a direct effect on the pituitary gland. The result is quicker action. They also pose a lower risk for complications and side effects.

Aromatase Inhibitors.Drugs that inhibit aromatase, an enzyme that is a major source of estrogen, are being studied for effects against endometriosis. Such drugs include anastrozole, letrozole, exemestane, and vorozole. Aromatase levels may be abnormal in women with endometriosis. A 2004 pilot study of letrozole combined with a progestin showed reduction of endometriosis as well as decrease in pelvic pain, suggesting that this treatment holds promise.

Selective Estrogen-Receptor Modulators (SERMs). Drugs known as selective estrogen-receptor modulators (SERMs) are thought to act like estrogen in some tissues but behave like estrogen blockers (antiestrogens) in others. They have not been widely studied for endometriosis since tamoxifen (Nolvadex), the most commonly used SERM, may worsen endometriosis. The actions of some other SERMs, however, such as raloxifene (Evista) or tibolone (only available in Europe at present), may be beneficial and warrant more research.

Selective Progesterone Receptor Modulators (SPRMs). SPRMs, also called mesoprogestins, have both agonist and antagonist properties. This new class of drugs may be effective for suppressing endometrial growth.

Other investigative drugs for treatment of endometriosis include tumor necrosis factor alpha (TNF-alpha) inhibitors, angiogenesis inhibitors, and various immune modulators.