Endometriosis - Medications

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• Add-back therapy provides doses of estrogen and progestin that are high enough to maintain bone density, but are too low to offset the beneficial effects of the GnRH agonist. Studies suggest this is safe and effective for protecting bone.
• Intermittent leuprolide uses repeated 6-month courses of GnRH agonists followed by an average of 9 months of symptom control only.
• Taking GnRH agonists in very low doses is an alternate approach, but is still largely untested.
• Adding bone-protective drugs may be helpful. The standard ones are bisphosphonates and include alendronate (Fosamax), risedronate (Actonel), and etidronate (Didronel). Other drugs are being tested in combination with a GnRH agonist to preserve bone. They include the parathyroid hormone teriparatide (Forteo) and selective estrogen-receptor modulators (SERMs), such as raloxifene (Evista).

GnRH treatments used alone do not prevent pregnancy. Furthermore, if a woman becomes pregnant during their use, there is some risk for birth defects. Women who are taking GnRH agonists should use non-hormonal birth control methods, such as the diaphragm, cervical cap, or condoms while on the treatments.

Danazol

Danazol (Danocrine) is a synthetic drug that resembles a male hormone (androgen). It suppresses the pathway leading to ovulation. Studies have shown symptomatic improvement in 90% of women, although in one study, only about 58% of women expressed satisfaction with this therapy. A high drop-out rate occurs, most often because of adverse side effects, particularly male characteristics, such as growth of facial hair, acne, weight gain, dandruff and deepening of the voice.

Danazol may increase the risk for unhealthy cholesterol levels. A few cases of blood clots and strokes have also been reported, as well as rare cases of liver damage. One study reported that taking a low dose may relieve endometrial symptoms and reduce the risk for these side effects. Exercise may also help reduce side effects. As with GnRH drugs, pregnant women or those trying to become pregnant should not take this drug because it may cause birth defects.

Antiprogestins

Antiprogestins are promising drugs for endometriosis because they reduce both estrogen and progesterone receptors.

Gestrinone. Gestrinone is the most studied antiprogestin and appears comparable to GnRH agonists in reducing pain and while causing fewer menopausal symptoms. In one study, bone density even increased slightly. Adverse effects of gestrinone include male hormone symptoms, such as acne, and possibly the development of unhealthy cholesterol levels.

Mifepristone. Mifepristone (Mifeprex) is another antiprogestin that may be helpful for treating endometriosis. In one 6-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.

Pain Medication

Nonsteroidal Anti-inflammatory Drugs (NSAIDs). Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) may be sufficient for about 75% of women with endometrial pain. NSAIDs block prostaglandins (the substances that increase uterine contractions). They are effective painkillers and also have other properties that act against inflammatory factors. Aspirin is the most common NSAID, but there are dozens of others available over the counter or by prescription. Among the most effective NSAIDs for menstrual disorders are ibuprofen (Advil, Motrin, Midol PMS), naproxen (Aleve, Naprosyn, Naprelan, Anaprox), and mefenamic acid (Ponstel). For maximum benefit, they should be taken 7 to 10 days before a period is expected. However, long-term use of NSAIDs can increase the risk for gastrointestinal bleeding and ulcers. One study of women with iron deficiency anemia reported that overuse of NSAIDs for menstrual disorders contributes to anemia.

Acetaminophen. Acetaminophen (Tylenol) reduces levels of female hormones (gonadotropins and estradiol, an estrogen), which may have some beneficial effect on menstrual disorders. A combination of acetaminophen and pamabrom (Women's Tylenol Menstrual Relief) is specifically aimed at treating menstrual pain and bloating. (Pamabrom is a diuretic, a drug used to reduce fluid build-up and bloating.)

Opioids. Drugs containing codeine should not generally be used for endometriosis pain management. They can cause pelvic congestion and constipation, which can worsen symptoms in patients with gastrointestinal distress.

Investigative Drugs

GnRH Antagonists. GnRH antagonists include ganirelix (Antagon) and cetrorelix (Cetrotide). These newer drugs 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. However, the actions of other SERMs such as raloxifene (Evista) or tibolone (only available in Europe), 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.

Review Date: 06/13/2006
Reviewed By: Harvey Simon, M.D., Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital