People in treatment are less likely to inject drugs. According to the government, approximately 5 million drug users were in need of treatment in 1998, while less than half that number received it. Methadone maintenance is the most effective treatment for heroin, the most commonly injected drug. But this treatment is available to only about 1 in 5 heroin users. Even in the best of all possible worlds, with drug treatment available to all who wanted it, we would still need to be concerned about improving access to sterile needles.
Drug dependence is a chronic, relapsing disease.
Some in treatment will, in fact, relapse. All these considerations lead to the significant conclusion that expanding drug treatment alone cannot stop the spread of HIV among people who inject drugs. Access to sterile needles is also needed. New federal rules for methadone maintenance have been proposed that are intended to increase accessibility, quality, and oversight of methadone treatment. U.S. Department of Health and Human Services.