Effectiveness of drug dependence treatment in HIV prevention

This review considers the effectiveness of drug dependence treatment in preventing HIV transmission among injecting drug users (IDUs). Substitution programmes using agonist pharmacotherapy (e.g. methadone and buprenorphine maintenance treatment) are available only for drug users who are primarily opioid dependent. There are over half a million people in receipt of methadone maintenance treatment (MMT) and it is estimated that this number will double in the coming decade. There is evidence that MMT is associated with a significant decrease in injecting drug use and sharing of injecting equipment. Data on sex-related risk behaviour change are limited, but suggest that MMT is associated with a lower incidence of multiple sex partners or exchanges of sex for drugs or money, but no change, or only small decreases, in unprotected sex. Studies of seroconversion, which is the toughest and most robust standard for assessing the role of MMT in HIV prevention, suggest that the reductions in risk behaviours do translate into actual reductions in cases of HIV infection. While the data on HIV risk behaviour are limited, there is strong evidence that substitution treatment with either methadone or buprenorphine suppresses illicit opioid use. There is also evidence that substitution treatment for HIV-positive IDUs is associated with better compliance with anti-retroviral treatment and improved health outcomes. The only antagonist being used for opioid dependence relapse prevention treatment is naltrexone. There is currently insufficient evidence to draw firm conclusions as to its effectiveness. Behavioural interventions add to the effectiveness of substitution treatment, while the effectiveness of different types of psychological therapy alone has been found to be variable. There have been few comparative studies of abstinence-based treatment, however, available evidence indicates good outcomes for those who remain in treatment for three months or more. All countries with a population of IDUs should aim to develop a comprehensive range of treatments, including substitution treatment, as a critical component of HIV prevention.