Danazol

Danazol is an androstane steroid derived from the progestogen ethisterone. Pharmacologically it is a weak androgen and anabolic steroid that also has antigonadotropic activity, meaning it damps down the pituitary hormones that drive the ovaries ^[2]. This combination of a mild androgenic effect with suppression of the reproductive axis underlies most of its medical uses.

The drug was synthesized in 1963 by scientists at Sterling Winthrop and approved by the U.S. Food and Drug Administration in 1971 as the first agent specifically indicated for endometriosis. It has been marketed under Danocrine and numerous other brand names.

In endometriosis, danazol produces a low-estrogen, mildly androgenic internal state that shrinks endometrial implants and relieves pelvic pain; in a network meta-analysis of treatments for endometriosis-related pain it appears among the available options, although hormonal contraceptives, progestins, and GnRH agonists are now generally preferred ^[1]. Preclinical work in animal models likewise shows danazol reducing the size of endometriotic lesions ^[4]. The drug has additionally been used for benign fibrocystic breast disease, heavy menstrual bleeding, and immune thrombocytopenia.

Danazol also has an established role in hereditary angioedema, where it is one of the attenuated androgens long used for long-term prophylaxis to lower the frequency of swelling attacks. Because of its androgenic burden, current guidance increasingly places it as a second-line option behind newer C1-inhibitor replacement and targeted therapies, and recent expert consensus focuses specifically on how to monitor patients on danazol and when to discontinue it ^[2][3].

The drug's androgenic effects, which include acne, unwanted hair growth, weight gain, unfavorable blood lipid changes, potential liver effects, and irreversible deepening of the voice, are the main constraint on its use, and it is contraindicated in pregnancy because it can masculinize a female fetus ^[2][3]. Danazol is a prescription-only medicine supplied as oral capsules.

Danazol is prescription only and its androgenic effects limit its use. Women may notice weight gain, acne, oily skin, unwanted hair growth, and, less reversibly, deepening of the voice, so it is stopped if voice changes begin. It must not be used in pregnancy because it can masculinize a female fetus, and effective non-hormonal contraception is advised. It can raise liver enzymes, cause liver tumors or peliosis with long use, worsen lipid profiles, and promote fluid retention, so it is used cautiously in heart, kidney, or liver disease. It interacts dangerously with statins by raising the risk of muscle breakdown, and it can increase the effect of warfarin and carbamazepine.

Danazol is a strong inhibitor of CYP3A4, and that single property drives most of its interactions. It raises cyclosporine and tacrolimus concentrations enough to bring on nephrotoxicity, and it pushes carbamazepine toward the toxic range. Statins that depend on CYP3A4, including simvastatin, lovastatin and atorvastatin, accumulate alongside it; myopathy and frank rhabdomyolysis have been reported from the combination.

Anticoagulation is the other serious pairing. Danazol prolongs prothrombin time in people stabilized on warfarin, acting partly on clotting factor synthesis rather than metabolism alone, and bleeding has followed. INR shifts can appear days after danazol is started or stopped.

Danazol also worsens insulin resistance, so glucose control in diabetes tends to drift upward while it is being taken. Its hepatotoxicity is dose related and additive with other liver-toxic drugs, which matters most for anyone already on methotrexate or an azole antifungal.

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Danazol is a synthetic steroid derived from ethisterone, developed by the pharmaceutical company Sterling-Winthrop and first described in the scientific literature in the early 1970s. It reached the United States market in 1976 under the brand name Danocrine and holds the distinction of being the first drug approved in that country specifically for the treatment of endometriosis. Its capacity to suppress reproductive hormone signaling and create a low-estrogen environment made it useful for endometriosis and fibrocystic breast disease, while a separate property, its ability to raise the liver's production of C1 esterase inhibitor, established it as a valuable long-term prophylactic against attacks of hereditary angioedema.

In more recent years researchers have explored a striking new use: because sex hormones can up-regulate the telomerase gene, a landmark 2016 study from the United States National Institutes of Health showed that danazol could lengthen telomeres and improve blood counts in patients with inherited telomere diseases. Although its androgenic side effects have led newer agents to replace it for several classic indications, danazol remains a clinically important medicine with an evolving profile.

Danazol carries the reputation of a versatile, historically important medicine, remembered as the first agent approved in the United States specifically for endometriosis and still valued for uses that few alternatives address as well. In hereditary angioedema it has long provided reliable protection against dangerous swelling attacks by boosting a key regulatory protein, a benefit that keeps it relevant despite the arrival of newer therapies.

Its most remarkable modern chapter is in the field of aging and bone-marrow failure, where a National Institutes of Health trial demonstrated that it could actually lengthen telomeres and restore blood counts in patients with rare telomere disorders, an outcome that has drawn wide scientific interest. Clinicians appreciate that it is taken orally and is well characterized after decades of use. A candid assessment recognizes that its androgenic side effects, such as acne, muscle cramps, and altered lipids, mean it is now used selectively and with appropriate monitoring.