Sexual orientation differences among men in a randomized clinical trial of extended-release naltrexone and bupropion for methamphetamine use disorder

Background: Methamphetamine use disorder (MethUD) disproportionately affects men who have sex exclusively with men or with men and women (collectively MSM/W), compared to men who have sex with women (MSW). This study is the first MethUD medication trial to compare treatment effect for these groups, hypothesizing that extended-release injectable naltrexone 380 mg every 3 weeks plus oral extended-release bupropion 450 mg daily would be less effective for MSM/W than MSW. Methods: Data come from men (N = 246) in a multi-site, double-blind, randomized, placebo-controlled trial with sequential parallel comparison design. In Stage 1 (6-weeks), participants were randomized to active treatment or placebo. In Stage 2 (6-weeks), Stage 1 placebo non-responders were rerandomized. Treatment response was ≥3 methamphetamine-negative urine samples, out of four obtained at the end of Stages 1 and 2. Treatment effect was the active-versus-placebo between-group difference in the weighted average Stages 1 and 2 responses. Results: MSM/W (n = 151) were more likely than MSW (n = 95) to be Hispanic, college-educated, and living with HIV. Adjusting for demographics, among MSM/W, response rates were 13.95 % (active treatment) and 2.78 % (placebo) in Stage 1; 23.26 % (active treatment) and 4.26 % (placebo) in Stage 2. Among MSW, response rates were 7.69 % (active treatment) and 5.80 % (placebo) in Stage 1; 3.57 % (active treatment) and 0 % (placebo) in Stage 2. Treatment effect was significantly larger for MSM/W (h = 0.1479) than MSW (h = 0.0227) (p = 0.04). Conclusions: Findings suggest efficacy of extended-release naltrexone plus bupropion for MSM/W, a population heavily burdened by MethUD. While a secondary outcome, this intriguing finding merits testing in prospective trials.