Treatment of idiopathic erectile dysfunction in men with the opiate antagonist naltrexone--a double-blind study

Opiate antagonists can indirectly stimulate the secretion of luteinizing hormone (LH) and testosterone, as well as sexual functions in animals and humans. We therefore treated 20 otherwise healthy men with idiopathic erectile dysfunction aged 46.3 +/- 2.7 years (mean +/- SE, range 23.9-63.3) in a double-blind study with an opiate antagonist, naltrexone, or placebo. The erectile dysfunction of these men had persisted for 3.6 +/- 0.5 years despite libido maintenance; standard procedures had excluded any organic causes. Trial duration was 12 weeks overall. After a 4-week forerun, the patients received at first 25 mg naltrexone/day orally or placebo for 4 weeks followed by 4 weeks of a 50-mg dose of naltrexone/day or placebo. Each day the patients filled out a questionnaire detailing libido, degree of erection, frequency of sexual intercourse, and spontaneous morning erections. Serum concentrations of gonadotropins and testosterone were determined radioimmunologically in the initial stage and at the end of each phase. Both patient collectives had similar initial factors. The group treated with naltrexone showed a significant rise in spontaneous early morning erections during the treatment: from 2.8 +/- 0.3 to 4.2 +/- 0.3 a week (P < 0.001). The placebo group showed no significant change in spontaneous erections (2.4 +/- 0.3 and 2.6 +/- 0.3, respectively). The subjective parameters, however, such as libido, degree of erection, and frequency of sexual intercourse showed no significant difference within each group. There was no difference in LH, follicle-stimulating hormone, or testosterone concentrations in both groups. Thus, treatment with naltrexone significantly raises the rate of spontaneous early morning erections when compared to controls.(ABSTRACT TRUNCATED AT 250 WORDS)