The efficacy and safety of the
gonadotropin-releasing hormone agonist
nafarelin for treatment of
endometriosis were compared with those of
danazol in two large-scale, double-blind trials. Assessments of severity of symptoms, laparoscopic scores before and after
therapy, and pregnancy rates showed that
nafarelin, 400 and 800 micrograms administered intranasally, was as efficacious as oral
danazol, 600 and 800 mg. The adverse effects seen with
nafarelin, mainly
hot flashes, were related to its mode of action, namely hypoestrogenemia induced by reversible inhibition of ovarian
hormone production. Hypoestrogenemia was associated with a decrease of bone density in the lumbar vertebrae, but these changes were partially or completely reversible
after treatment was discontinued. No significant changes in bone mass occurred in the distal radius.
Danazol was associated with androgenic and metabolic adverse effects, including
weight gain, negative effects on the
lipid profile, and elevated liver
enzyme levels.
Nafarelin was found to be as effective as
danazol for the management of
endometriosis, with a different and more favorable safety profile.