Endometriosis - Medications

Estrogen and progestin each cause different side effects. The most serious side effects are due to the estrogen in the combined pill. Uncommon but more dangerous complications of OCs include high blood pressure and deep-vein blood clots (thrombosis), which may contribute to heart attacks or strokes in rare cases. It should be noted that a long-term study of 46,000 British women found no difference in mortality rates between women who took OCs and those who did not. Studies have been conflicting about whether estrogen in oral contraception increases the chances for breast cancer, and if it does, which women are at risk. A reassuring 2002 study supported an earlier major study, with both finding no evidence that OC use increases the risk for breast cancer, even in women who have taken them for 15 years of more or had taken them at young ages. Still, more research is needed to verify these findings, given previous reports of a slightly higher risk.

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Progestins

Progestins alone may be helpful and are the oldest drugs used for endometriosis. Progestins can prevent ovulation and reduce the risk for endometriosis in the following ways:

They block luteinizing hormone (LH), one of the reproductive hormones important in ovulation.
They change the lining of the uterus and eventually cause it to atrophy.
One study reported that progestins provide temporary pain relief equivalent to the more powerful hormone drugs, such as danazol or a GnRH agonist. Some experts recommend them as the first choice for women with endometriosis who do not want to become pregnant. Progestins given during the luteal phase do not appear to be beneficial. (This is the premenstrual phase, which is 14 days before a period.)

Specific Progestins. Progestins are available in pill or injectable form, or as a progestin-releasing intrauterine device (IUD). Medroxyprogesterone (Depo-Provera), which is administered by injection typically every three months, is one of the standard progestins used. A new formulation, Depo-subQ Provera 104, was approved in 2005. Oral progestins include norethindrone (Micronor, Aygestin, Norlutate). Norethindrone is also known as norethisterone.

Progestin-releasing IUDs can be very helpful for many women with endometriosis, particularly an advanced version called the levonorgestrel-releasing intrauterine system, or LNG-IUS (Mirena). Studies are suggesting that the LNG-IUS reduces endometrial cell proliferation and increases cell self-destruction. Progestin released by the IUD mainly affects the uterus and cervix and causes fewer widespread side effects than other forms of progestins. The LNG-IUS has proved effective for heavy bleeding (menorrhagia) and studies are indicating that it is also effective in controlling the symptoms of minimal to moderate endometriosis.