Methadone treatment was associated with more than a 50% reduction in the risk of HIV transmission in injecting drug users, in a meta-analysis published in the BMJ.

The researchers sought evidence from 12 published, and three unpublished, observational studies to quantify the reduction in HIV transmission associated with opiate substitution treatment. All the studies involved methadone treatment, and data from nine studies were chosen to pool into a meta-analysis. These studies covered a total of 819 incident HIV infections over 23,608 person-years of follow-up.

Methadone treatment was associated with a 54% reduction in the risk of HIV infection, rate ratio 0.46 (95% CI:0.32-0.67;P < 0.001). Weaker evidence suggested that longer duration of treatment with methadone might be associated with greater benefit.

The authors acknowledged the observational nature of the studies and the potential for bias.

Of the public health arguments for opioid substitution treatment for heroin dependence and injecting use, prevention of HIV transmission is one of the more persuasive.

Earlier systematic reviews have demonstrated that treatment with methadone or buprenorphine is associated with a reduction in behaviours associated with HIV transmission, including a decrease in injecting use and sharing of injecting equipment, and a fall in numbers of sexual partners and prostitution. However, until now, there has been no quantitative analysis of the extent by which substitution treatment reduces HIV transmission.

Opiate substitution treatment was associated with a clear benefit for people who inject drugs, and should be supported as a public health measure.

Dr Jez Thompson

• MacArthur GJ, Minozzi S, Martin N et al. Opiate substitution treatment and HIV transmission in people who inject drugs: systematic review and meta-analysis. BMJ 2012;345:e5945