Danazol is a synthetic hormone, and used to be commonly prescribed as one type of treatment for endometriosis. It acts by suppressing the brain's production of follicle stimulating hormones and hence suppresses ovarian function. This is similar to an artificial menopause and results in the shrinking of not only the endometrium in the uterus (and hence no periods); but also hopefully the misplaced patches of endometrium outside the uterus found in patients with endometriosis, causing them to disappear.
Side Effects: Hot flushes, weight gain, acne, hirsutism (hairiness). These side effects are quite troublesome, and some women have to discontinue the drug because of these. Usually, while taking the danazol, your periods will stop completely - pseudomenopause.
Dose: The standard dose used to be 800 mg daily (4 tablets of 200 mg each). However, the side-effects at this dose are considerable, and many doctors have reported good results with doses as low as 200 mg daily. The usual course of treatment is 6-9 months and the extent of the improvement in endometriosis is then reviewed.
While danazol is useful for suppressing the lesions of endometriosis, it is not useful for treating endometriosis in infertile women. While taking the danazol , ovulation is suppressed, and because all it achieves is temporary suppression of the lesions, once you stop the danazol , the endometriosis recurs. This is why it is usually not advised for treating infertile women with endometriosis anymore, because it has not been shown to be helpful in improving pregnancy rates.