Background. To ascertain the role of endogenous opioids in sexual response, naltrexone, an opiate receptor antagonist, was administered to men, and its effect on selected self-report measures of sexual response to masturbation was recorded. Methods. The data are based on results from 20 healthy, sexually active (alone or with a partner) men, aged 20-29 years, who ingested naltrexone (25 mg/day × 3) or placebo in a randomized, double-blind crossover design. There was at least a 14-day interval between drug and placebo treatment. Between 18 and 22 h after the most recent dose of drug or placebo, subjects viewed sexually explicit videos in privacy for 2 h. They were instructed to masturbate and have as many orgasms as desired. The following three different self-report measures of their responses were recorded: number of orgasms; intensity of sexual arousal, and orgasmic intensity. Results. Under the naltrexone condition, the volunteers experienced a significantly greater mean number of orgasms (3.4 ± 0.2 SEM) than under the placebo condition (2.6 ± 0.3). The total number of orgasms was 67 under the naltrexone condition and 51 under the placebo condition. At the first orgasm, the measure of intensity of arousal was significantly greater in the naltrexone (3.9 ± 0.2) than placebo (3.4 ± 0.2) condition, and the measure of orgasmic intensity was significantly greater in the naltrexone (3.7 ± 0.2) than in the placebo (3.0 ± 0.3) condition. Conclusions. The present study provides evidence that endogenous opioids modulate orgasmic response and the perceived intensity of sexual arousal and orgasm in men. The findings suggest that naltrexone could be clinically useful in cases of inhibited sexual desire and erectile dysfunction.
All Science Journal Classification (ASJC) codes