Nafarelin acetate: a gonadotropin-releasing hormone agonist for the treatment of endometriosis.

Nafarelin acetate is a gonadotropin-releasing hormone (GnRH) agonist proven as effective as danazol in treating endometriosis. Its proposed mechanism of action is the desensitization of pituitary GnRH receptors leading to a decrease in gonadotropin release, and ovarian hormone serum concentrations similar to those achieved in postmenopausal women. Nafarelin decreases or ablates the physical symptoms associated with endometriosis, and pregnancy rates following therapy with this drug are comparable to rates observed after danazol therapy. Nafarelin is administered by nasal inhalation and has been generally well tolerated. It is associated with a high incidence of adverse effects but they are rarely severe enough to cause withdrawal from treatment, and those occurring most frequently--hot flashes, vaginal dryness, and decreased libido--are a consequence of the hypoestrogenemia induced by the drug. Increased bone turnover occurs in women on nafarelin but biochemical parameters return to pretreatment concentrations by six months after termination of treatment. This agent's place in the therapy of endometriosis will be determined as clinical experience accumulates.