Risk factors for methadone outside treatment programs: implications for HIV treatment among injection drug users

BACKGROUND: Diversion of methadone outside treatment programs occurs, yet reasons for use of 'street methadone' are characterized poorly. Self-medication for withdrawal symptoms is one plausible hypothesis. Among HIV-infected drug users, some antiretroviral medications can reduce potency of methadone, yet any association between such effects and the use of supplemental methadone sources remains undetermined. OBJECTIVE: To estimate the frequency and risk factors for use of street methadone. METHODS: Injection drug users (IDUs) recruited through extensive community outreach in 1988-89 and 1994 were followed semi-annually with questionnaires about health history, use of licit and illicit drugs including methadone and HIV-related assays. Analyses were performed using generalized estimating equation logistic regression. RESULTS: Of 2811 IDUs enrolled and eligible for analysis, 493 people reported use of street methadone over 12 316 person-years of follow-up (4.0/100 person-years). In multivariate analyses, street methadone use was more common among women, whites, those 40-59 years old, those who reported withdrawal symptoms, past methadone program attendance (6-12 months before visit), recent heroin injection with or without cocaine (but not cocaine alone), smoking or sniffing heroin and reported trading sex. Street methadone was not associated with HIV infection or treatment. CONCLUSION: The results suggest that older IDUs still using heroin may be using street methadone to treat signs of withdrawal. The absence of a higher rate of street methadone use in HIV seropositive IDUs reveals that antiretroviral/methadone interactions are not a primary determinant of use outside of treatment settings.