Danazol

Key facts

• Danazol is a synthetic androgen (male-hormone-like steroid) that suppresses ovarian hormone production and reduces estrogen-driven tissue growth.
• It is taken by mouth, usually daily, in courses lasting months; effects on pain and swelling build over weeks.
• Danazol can cause virilization: a deepened voice, excess facial or body hair, acne and an enlarged clitoris, some of which do not reverse when the drug is stopped. It also carries risks of liver toxicity and blood clots, and it is contraindicated in pregnancy because it can virilize a female fetus.
• Seek urgent care for yellowing of the skin or eyes, severe abdominal pain, or pain and swelling in one leg.

What danazol treats

Danazol treats endometriosis, easing pelvic pain and reducing abnormal tissue growth, and fibrocystic breast disease, relieving breast pain and lumpiness. It also prevents attacks of hereditary angioedema, a genetic condition causing sudden swelling of the face, throat, airway or gut, and is occasionally used to raise low platelet counts in some blood disorders. It is not a first-line treatment for any of these conditions and is generally reserved for when other options have failed, because of its hormonal side effects.

How danazol works

Danazol suppresses the pituitary hormones that drive ovarian estrogen production, creating a low-estrogen, androgen-dominant state that shrinks endometrial tissue and eases breast tenderness. It also raises levels of a liver protein, C1 esterase inhibitor, that helps prevent the swelling attacks of hereditary angioedema.

Before you take it

• Do not take danazol if you are pregnant, could become pregnant, or are breastfeeding: it can virilize a female fetus. Use non-hormonal contraception while taking it, since it can also affect hormonal contraceptives.
• Tell your prescriber about liver disease, a history of blood clots, migraine, or high blood pressure; these can rule it out or need extra monitoring.
• Danazol changes cholesterol levels and can worsen conditions affected by fluid retention, such as heart or kidney disease.
• Other medicines that affect the liver, and anticoagulants, whose effect danazol can increase, should be flagged to your prescriber.

Side effects

Common effects include acne, oily skin, weight gain, fluid retention, and menstrual changes such as lighter periods or spotting.

Stop and seek urgent medical care for any of these:

• Yellowing of the skin or eyes, or severe abdominal pain.
• Pain, swelling or warmth in one leg, or sudden chest pain or breathlessness.
• Voice changes, excess hair growth or other signs of virilization: report these promptly, as continuing treatment can make them permanent.

Safety essentials

• Danazol's defining risks are virilization, liver toxicity and blood clots. Liver function is checked before starting and periodically during treatment, and the lowest effective dose is used for the shortest necessary time.
• Stop danazol immediately and get medical advice at the first sign of voice deepening or unwanted hair growth: some virilizing effects are irreversible even after stopping.
• Never use danazol in pregnancy; confirm you are not pregnant before starting and use non-hormonal contraception throughout treatment.
• Buy danazol only from a licensed pharmacy.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.