The risk of HIV infection by people who inject drugs can be halved by using methadone or other opiate substitution treatments, according to a review of global studies.
The review, by authors from Australia, Europe, Canada and the US and published in the British Medical Journal, analysed nine studies of mainly males between 26 and 39 and data related to hundreds of incidents of HIV infection.
The analysis found that opiate substitution treatment (OST) was associated with reductions in the frequency of injecting, the sharing of injection equipment and other changes in behaviour.
"Involvement in such treatment, as part of a package of interventions, might also increase engagement with health services and access to care and services focused on HIV prevention," the rearchers said.
The findings also might reflect comparatively high levels of motivation to change behaviour among individuals exposed to OST.
In an accompanying editorial, Adelaide researcher Linda Gowing said the latest review, combined with an earlier one, provided strong evidence methadone reduces high risk behaviours associated with intravenous drug use and the risk of acquiring HIV.
"By achieving these two things, opioid substitution treatment could reduce HIV transmission more widely because people who inject drugs can also transmit HIV to non-drug users through sexual contact," she said.
She noted OST had a greater effect on drug-related risk behaviours than on risk behaviours related to sexual encounters, particularly condom use.
"Greater attention now needs to be paid to interventions aimed at changing sexual risk behaviour in people receiving opioid substitution treatment, with a view to further reducing the transmission of HIV."