Reducing Substance Use and Associated Risk Behaviors with Pharmacotherapy

Substance use is a modifiable risk factor for HIV transmission among men who have sex with men (MSM). Multiple studies have linked substance use to sexual risk behaviors and HIV infection among MSM. Additionally, studies have documented that significant declines in the HIV risk were associated with parallel declines in substance use. Therefore, effective interventions for substance use have the potential to reduce HIV risk among MSM.

Our research group at the San Francisco Department of Public Health recently published an article in the Journal of Acquired Immune Deficiency Syndromes (JAIDS) on the results of Project iN: intermittent naltrexone study. This study observed that the use of a medication on an as-needed basis is a feasible, acceptable, and tolerable intervention strategy for non-dependent methamphetamine-using and binge-drinking (defined as 5 or more drinks on a single occasion) MSM. In this study, we randomly assigned 30 substance-using MSM (SUMSM) to either oral naltrexone or placebo, and asked participants to take the study medication when having cravings or in anticipation of methamphetamine or heavy alcohol use. The results of this pilot study were very encouraging for the following reasons:

  • We found that non-dependent SUMSM are willing to participate and be retained in a placebo-controlled pharmacologic trial. Additionally, 96% of SUMSM in the study reported being satisfied or highly satisfied with participating in the trial. Most pharmacologic studies have focused on substance-dependent participants. Observing high retention, completion, and satisfaction rates among non-dependent SUMSM in a pharmacologic trial is a very positive finding for the field!
  • We observed that taking a medication on an as-needed basis is acceptable among SUMSM. According to our electronic monitoring devices, on average, participants in the study used the medication twice per week in anticipation of methamphetamine or heavy alcohol use. Most pharmacologic studies with oral medications have required participants to take pills daily, which is not always feasible. Our data suggest that intermittent, as-needed dosing can be a promising alternative. We believe this non-daily, as-needed approach may resonate better with non-dependent SUMSM as well, since they do not use substances on a daily basis.
  • We also found that taking oral naltrexone was safe among active methamphetamine users and binge-drinkers. There were no serious side effects in the study and none of the participants reported stopping the medication because of the effects it had on their body.
  • For some individuals, taking naltrexone as needed was associated with reductions in methamphetamine and binge drinking. For SUMSM who used methamphetamine at least weekly, those received naltrexone significantly reduced the number of days they used methamphetamine, compared to those who received placebo. Additionally, SUMSM who took naltrexone at least three times per week significantly reduced the number of binge drinking days, compared to those who received placebo. Even though we did not observe a protective effect from naltrexone among all SUMSM, for some individuals in the study, the medication was helpful in reducing their methamphetamine use and binge-drinking, compared to placebo.
  • Naltrexone was associated with significant sexual risk reductions. Compared to placebo, those who received naltrexone had significant reductions in serodiscordant receptive anal intercourse and serodiscordant condomless receptive anal intercourse. To our knowledge, this is the first study of oral naltrexone to demonstrate significant reductions in HIV-related sexual risk behaviors among SUMSM.

Taken together, the findings from our pilot study are very encouraging. However, larger studies are needed to confirm the results of Project iN. In any case, our data highlight future opportunities to utilize pharmacotherapy as a potential substance use treatment and HIV prevention strategy among SUMSM. If proven successful in larger efficacy trials, pharmacologic approaches may be added to our clinical armamentarium for combination HIV prevention approaches, alongside Pre-Exposure Prophylaxis (PrEP) strategies, condoms and other evidence-based approaches. Pharmacologic approaches may also expand intervention strategies for some SUMSM who may not be interested in or able to use PrEP, but who may have interest in reducing their substance use and associated harm. Ultimately, our group hopes to continue to build on these findings to continue to expand our tool kit “to meet people where they are at” and support the wide spectrum of health goals for SUMSM.


For more: Santos GM, Coffin P, Santos D, Huffaker S, Matheson T, Euren J, DeMartini A, Rowe C, Hahn JA, Vlahov D, Vittinghoff E, Batki SL. Feasibility, acceptability and tolerability of targeted naltrexone for non-dependent methamphetamine-using and binge-drinking men who have sex with men. J Acquir Immune Defic Syndr. 2015 Dec 15.

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