Endometriosis - Medications

The most important concern is possible osteoporosis from estrogen loss. Women ordinarily should not take them for more than six months. Certain approaches may preserve enough estrogen to protect bones and still effectively relieve endometriosis symptoms:

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 six-month courses of GnRH agonists followed by an average of nine months of symptom control only.
Taking GnRH agonists in very low doses is an alternate approach, but is still largely untested.
Adding a bone-protective agents may be helpful. The standard ones are bisphosphonates and include alendronate (Fosamax), risedronate (Actonel), and etidronate (Didronel). Other agents 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).

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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 substance 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 help reduce side effects. As with GnRH agents, pregnant women or those trying to become pregnant should not take this drug because it may cause birth defects.

Antiprogestins

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

Gestrinone. Gestrinone is the most studied antiprogestin and may be comparable to GnRH agonists in reducing pain and have 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.