UCSF

Background and aims

Methamphetamine use is increasingly prevalent and associated with HIV transmission. Early-phase human studies suggested naltrexone reduced amphetamine use among dependent individuals. We tested if extended-release naltrexone (XRNTX) reduces methamphetamine use and associated sexual risk behaviors among high-risk methamphetamine-dependent men who have sex with men (MSM).

Design

Double-blind, placebo-controlled, randomized trial of XRTNX versus placebo over 12 weeks from 2012 to 2015.

Setting

San Francisco Department of Public Health, California, USA.

Participants

One hundred community-recruited, sexually-active, actively-using methamphetamine-dependent MSM. Mean age was 43.2 years; 96% were male, 3% transfemale, and 1% transmale; 55.0% were white, 19.0% African American, and 18.0% Latino.

Interventions

XRNTX 380 mg (n = 50) or matched placebo (n = 50) administered by gluteal injection at 4-week intervals.

Measurements

Regression estimated average level and change in level of positive urines during the period 2-12 weeks (primary outcomes) and sexual risk behaviors (secondary outcome).

Findings

Ninety per cent of visits were completed. By intent-to-treat, participants assigned to XRNTX had similar differences during 2-12 weeks in methamphetamine-positive urines as participants assigned to placebo [incidence rate ratio (IRR) = 0.95, 95% confidence interval (CI) = 0.76-1.20; Bayes factor < 0.3]. Observed urine positivity declined from 78 to 70% in the XRNTX arm and 74 to 64% in the placebo arm. Adherence to injections was 96.7% in the XRNTX arm and 91.3% in the placebo arm. Sexual risk behaviors declined similarly among participants in both arms (all P > 0.05). There were no serious adverse events related to study drug and no differences in frequency of adverse events by treatment arm.

Conclusions

Notwithstanding very high medication adherence for this study, extended-release naltrexone does not appear to reduce methamphetamine use or sexual risk behaviors among methamphetamine-dependent men who have sex with men compared with placebo.