Methadone and buprenorphine-naloxone both associated with reduced HIV risk among people who inject drugs

Buprenorphine drop-out rate means that methadone is favoured

Michael Carter
Published: 29 April 2014

Methadone maintenance therapy and treatment with buprenorphine-naloxone are equally effective at reducing HIV injecting risk behaviours among people who inject drugs, investigators from the United States report in the online edition of the Journal of Acquired Immune Deficiency Syndromes.

Both treatments were associated with significant reductions in injecting practices linked to a risk of HIV transmission. Sexual risk behaviour also decreased in women taking both therapies. However, drop-out rates were higher among people treated with buprenorphine-naloxone and men taking this therapy reported significantly higher rates of sexual risk-taking.

“These findings show marked and approximately equal reductions in injection and injection related risk among participants who remained on their assigned treatment,” write the authors. “Buprenorphine-naloxone, like methadone, is a successful HIV risk reduction intervention for patients who remain in treatment, but with the added advantage of being accessible in settings other than methadone programs in the US.”

People who inject drugs are one of the groups most affected by HIV in many countries including the US. Methadone maintenance therapy has been shown to be an effective HIV risk-reduction strategy for people who inject drugs. The treatment has been associated with reduced opioid use, reduced needle sharing, reduced frequency of injecting and lower HIV incidence and prevalence.

Buprenorphine-naloxone can also be used as opioid substitution therapy. A small study showed that methadone maintenance therapy and buprenorphine-naloxone were equally effective at reducing injecting risk behaviours, but that only methadone was associated with consistent declines in sexual risk.

Investigators designed a larger study comparing the impact of methadone maintenance therapy and buprenorphine-naloxone on injecting and sexual risk. Data were obtained from participants enrolled in a study examining the effect of these two therapies on liver function.

Recruitment took place between May 2006 and October 2009 with follow-up until August 2010. Participants were originally randomised on a 1:1 basis. However, a higher drop-out rate among buprenorphine-naloxone recipients meant that this was changed to 2:1, buprenorphine to methadone.

Participants completed the HIV Risk Behavior Survey at baseline and at weeks 12 and 24. The survey included questions on injecting and sexual risk in the previous 30 days.

The total study population consisted of 731 individuals (methadone= 391; buprenorphine = 340) who completed the baseline risk survey. Of these, 96% completed the follow-up surveys at weeks 12 and 24.

These follow-up assessments showed that both therapies were associated with significant and comparable reductions from baseline in the frequency of injecting (p < 0.0008 or greater). There were also significant reductions in the proportion of participants who reported sharing injecting equipment, who did not clean their equipment with bleach, who shared cookers, engaged in front/backloading and in overall needle-associated risk (p < 0.0001). These reductions did not differ by treatment assignment.

However, the frequency of methamphetamine injecting increased among buprenorphine-naloxone recipients (p < 0.05) but declined among those assigned to methadone maintenance therapy. The investigators were unable to explain this and suggest it “may be an incidental finding as it has not been previously reported.”

Both treatment groups reported a reduction in the number of sexual partners. Analysis of sexual behaviour by gender showed that risk was reduced among women regardless of their treatment assignment. For males, the sexual score increased for those taking buprenorphine-naloxone but declined for those assigned to methadone maintenance therapy. The authors suggest this “could be a result of a greater impact on sexual hormone production among patients taking methadone, particularly males.”

They conclude their “findings further support the importance of expanding availability of evidence-based medical treatment for opioid addiction.”

The higher drop-out rate among patients treated with buprenorphine-naloxone “suggest that methadone may be generally more effective.”

Reference

Woody G et al. HIV risk reduction with buprenorphine-naloxone or methadone: findings from a randomized trial. J Acquir Immune Defic Syndr, online edition. DOI: 10.1097/QAI0000000000000165, 2014.