Danazol for endometriosis

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Danazol for endometriosis


Generic Name

An oral dose (pill) of danazol, 400 mg or 800 mg per day, is taken for 6 to 9 months.1

How It Works

Danazol is a drug that lowers estrogen levels and increases androgen levels. This puts the body in a state that is like menopause and can cause some male physical traits, as well. As a result, danazol:

  • Stops the ovaries' monthly release of a mature egg (ovulation).
  • Shrinks endometriosis growths (implants) and reduces endometriosis pain for most women.

Why It Is Used

Danazol is occasionally used to treat endometriosis, usually when all other hormone therapies have not helped. Danazol can:

  • Relieve pain.
  • Prevent endometriosis from getting worse.
  • Reduce the size of endometriosis implants.
  • Be used to shrink implants before surgery, which can help prevent internal scarring from the surgery.

Danazol is not widely used to treat endometriosis and other estrogen-related conditions, because it can cause serious side effects. Because of these serious side effects, such as increased cholesterol levels, danazol use is limited to 6 to 9 months at a time. Danazol may not be appropriate if you already have a high risk for developing increased cholesterol levels or liver disease.

Reasons not to use danazol include:

  • Undiagnosed abnormal vaginal bleeding.
  • Chronic liver, kidney, or heart disease, which can become worse with danazol therapy.
  • Pregnancy or possibility of pregnancy during treatment (danazol can harm a fetus).
  • Breast-feeding.
  • Inherited disorder of skin pigment (porphyria).

How Well It Works

Up to 90% of women who use danazol report improvement in symptoms of endometriosis.2 Relief is likely to be noticeable within a few months after starting treatment. Pain relief typically lasts for 6 to 12 months after stopping treatment.

Like all hormone therapies and surgery for endometriosis, danazol does not cure the disease.

Pain recurrence

After treatment with danazol or any hormone therapy, endometriosis pain can, but does not always return:2

  • Each year, up to 20% of all women treated will have pain that returns after hormone treatment.
  • About 37% of women who use hormone therapy for mild endometriosis have pain 5 years later.
  • About 74% of women who use hormone therapy for severe endometriosis have pain 5 years later.

Danazol does not improve infertility caused by endometriosis.

Side Effects

Danazol side effects are common, affecting 80% of women who take danazol. Up to 20% of women stop taking the medicine because of side effects.1 Most of these side effects go away within several months after stopping treatment, but deepening of the voice can be permanent. Side effects include:

  • Weight gain.
  • Muscle cramps.
  • Decreased breast size.
  • Flushing.
  • Oily skin and hair.
  • Depression.
  • Acne.
  • Increase in male characteristics, such as deepening of the voice and increased facial hair and body hair (hirsutism). A change in voice can be permanent.
  • Increased cholesterol levels.
  • Skin rash.

Danazol may increase ovarian cancer risk when used to treat endometriosis.3

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Danazol does not cause bone loss as GnRH-a therapy does, but danazol side effects are generally more severe than side effects from GnRH-a used with add-back therapy. (Add-back therapy involves taking a small amount of estrogen. This keeps estrogen just high enough that bone loss and menopausal side effects are not as severe as with GnRH-a alone.)

If you have an increased risk for developing high cholesterol or liver disease, your health professional will probably recommend a different treatment.

Do not use danazol if you are or could become pregnant. Because of potential harm to a developing fetus, it is essential to use a barrier method of contraception, such as condoms, to prevent pregnancy while taking danazol.1 Start taking the medicine during your menstrual period to avoid taking it while pregnant.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.



  1. Lobo RA (2007). Endometriosis. In VL Katz et al., eds., Comprehensive Gynecology, 5th ed., pp. 473–499. Philadelphia: Mosby Elsevier.
  2. Speroff L, Fritz MA (2005). Endometriosis. In Clinical Gynecologic Endocrinology and Infertility, 7th ed., pp. 1103–1133. Philadelphia: Lippincott Williams and Wilkins.
  3. Cottreau CM, et al. (2003). Endometriosis and its treatment with danazol or lupron in relation to ovarian cancer. Clinical Cancer Research, 9(14): 5142–5144.


By Healthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer Deborah A. Penava, BA, MD, FRCSC, MPH - Obstetrics and Gynecology
Last Revised December 8, 2009

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