Methadone Use Reduces Risk of HIV Infection among Injection Drug Users

Methadone maintenance therapy is associated with a lower risk of HIV infection among people who inject drugs, though this may be attributable in part to differing behavior among people who do and do not seek treatment for addiction, according to a report in the October 3, 2012, British Medical Journal.

Sharing syringes and other drug-injection equipment is a highly efficient means of transmitting HIV, hepatitis B and C, and other blood-borne pathogens. Needle exchange and distribution programs have been shown to reduce the risk of infection, and opiate substitution therapy using methadone -- which is administered as a pill or liquid -- may also play a role in reducing HIV incidence in this population.

In an effort to quantify the effect of opiate substitution on HIV infection rates among injection drug users, Georgie MacArthur from the University of Bristol, Julie Bruneau from the University of Montreal, and an international team of colleagues performed a systematic review and meta-analysis of published and unpublished prospective observational studies looking at this association.

A search of Medline, Embase, PsychINFO, and the Cochrane Library identified 12 published studies that examined the effect of methadone maintenance on HIV infection, and the researchers also obtained unpublished data from 3 additional studies. Overall, they found that methadone use was associated with a 54% reduction in the risk of HIV infection among injection drug users.

"Opiatesubstitution treatment provided as maintenance therapy is associated with a reduction in the risk of HIV infection among people who inject drugs," the study authors concluded. "These findings, however, could reflect comparatively high levels of motivation to change behavior and reduce injecting risk behavior among people who inject drugs who are receiving opiate substitution treatment."

Below is an edited excerpt from a press release issued by the University of Montreal describing the study and its findings.

Methadone Reduces the Risk of HIV Transmission

October 5, 2012 -- Methadone reduces the risk of HIV transmission in people who inject drugs (PWID), as reported by an international team of researchers in a paper published today in the online edition of the British Medical Journal (bmj.com). This team included Dr. Julie Bruneau from the CHUM Research Centre (CRCHUM) and the Department of Family Medicine at the Université de Montréal.

"There is good evidence to suggest that opiate substitution therapies (OST) reduce drug-related mortality, morbidity and some of the injection risk behaviors among PWID. However, to date there has been no quantitative estimate of the effect of OST in relation to HIV transmission. This new study provides solid evidence demonstrating the link between these treatments and a reduced risk of HIV transmission," notes Dr. Bruneau, one of the six investigators who worked with Dr. Matthew Hickman, the study's principal investigator and Professor in Public Health and Epidemiology at the University of Bristol (UK).

"These results are important given that increases in HIV incidence have been reported among PWID in a number of countries in recent years, where opiate substitution therapies are illegal or severely restricted," adds Dr. Bruneau.

Injection drug use is a major risk factor for the transmission of HIV and AIDS. It is estimated that around 5%-10% of HIV infections worldwide are due to injection drug use. Methadone and buprenorphine are the main forms of drug prescribed for addicts and are frequently prescribed as opiate substitution therapies.

The results of this study are the fruit of an international collaborative effort. Authors from the US, Canada, Italy and Australia carried out a review and pooled analysis (known as a meta-analysis) of several published and unpublished studies from multiple countries (including the US, Canada, the UK, the Netherlands, Austria, Italy, Thailand, Puerto Rico and China) to determine the association between OST and HIV transmission among PWID. The nine selected studies looked predominantly at males between 26 and 39 years old and totalled 819 incidences of HIV infection with 23,608 person-years of follow-up.

After analyzing these studies, authors found that OST was associated with a 54% reduction in risk of HIV infection among PWID. There were differences between the studies, including different background rates of HIV infection, making it impossible to calculate an "absolute risk reduction" for HIV infection that would translate to all settings. And not all studies reported adjustments to the intervention to take account of other factors that might influence the association between OST and HIV infection. But the impact of OST on HIV was strong and consistent in further analyses in the paper. There was weak evidence to suggest that longer duration of OST exposure may be associated with greater benefit.

For Dr. Bruneau, the results of this study favor the promotion of opiate substitution therapies: "These therapies can reduce HIV transmission among PWID not only in countries in which there is a high incidence of this disease, but also in Quebec where there has been an increase in the use of illicit opiates intravenously, particularly among youths, and where access to OST is problematic."

10/10/12

Reference

GJ Macarthur, S Minozzi, N Martin, et al. Opiate substitution treatment and HIV transmission in people who inject drugs: systematic review and meta-analysis. British Medical Journal 345:e5945. October 3, 2012.

Other Source

University of Montreal. Methadone Reduces the Risk of HIV Transmission. Press release. October 5, 2012.