Injection opioid use as a predictor of treatment outcomes among methadone-maintained opioid-dependent patients.

Background: Injection opioid use is associated with more severe health and psychosocial consequences relative to non-injection use, but few studies have examined whether injection use is associated with methadone maintenance treatment outcomes. The present study examined differential MMT outcomes among opioid injectors and non-injectors.

Methods: Data were extracted from the clinic charts of opioid-dependent MMT patients (N = 290; n = 115 injectors) enrolled in a university-affiliated, urban MMT clinic. Injection status was examined as a predictor of short- (3-month opioid, cocaine, benzodiazepine and cannabis urine drug screens) and long- (days retained in treatment) term MMT outcomes.

Results: Bivariate analyses revealed injection users were less likely to be African American and to have completed high school, were more likely to have started heroin use before age 21, to report having hepatitis C, to report a baseline cocaine use disorder, and had higher methadone doses at 3-months into treatment. Injection status significantly predicted a greater proportion of cocaine-positive urine drug screens in the first 3 months of treatment, but did not significantly predict opioid, benzodiazepine or cannabis drug screens, or length of treatment retention.

Conclusion: This is one of a handful of studies to examine injection status as a predictor of MMT outcomes. Injection status is associated with cocaine use early in treatment, which has implications for the focus of treatment.