Methadone reduces risk of HIV transmission in people who inject drugs, say experts

People who inject drugs (PWID) can significantly reduce their risk of HIV infection with the use of opiate substitution treatments such as methadone, as suggested by an international team of researchers in a paper published today on bmj.com.

Injection drug use (IDU) is a major risk factor for the transmission of HIV and AIDS and HIV / AIDS accounts for nearly one fifth of the burden of disease among people who inject drugs. It is estimated that around five to 10 per cent of HIV infections worldwide are due to IDU.

Methadone and buprenorphine are the main forms of drug prescribed for addicts and are frequently prescribed as opiate substitution therapies (OST). There is good evidence to suggest that OST reduces drug-related mortality, and some of the behaviours associated with injecting risk, but to date there has been no quantitative estimate of the effect of OST in relation to HIV transmission.

Authors from around the world (US, Canada, Europe and Australia) therefore carried out a review and pooled analysis of several published and unpublished studies from multiple countries (including USA, Canada, UK, the Netherlands, Austria, Italy, Thailand, Puerto Rico and China) to determine the association between OST and HIV transmission amongst people who inject drugs. The nine 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 analysing these studies, authors found that OST was associated with a 54-per cent reduction in risk of HIV infection among PWID. There were differences between the studies, including different background rates of HIV infection: this made 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.