Treatment retention among patients randomized to buprenorphine/naloxone compared to methadone in a multi-site trial

Aims: To examine patient and medication characteristics associated with retention and continued illicit opioid use in methadone (MET) versus buprenorphine/naloxone (BUP) treatment for opioid dependence.

Design, settings and participants: This secondary analysis included 1267 opioid-dependent individuals participating in nine opioid treatment programs between 2006 and 2009 and randomized to receive open-label BUP or MET for 24 weeks.

Measurements: The analyses included measures of patient characteristics at baseline (demographics; use of alcohol, cigarettes and illicit drugs; self-rated mental and physical health), medication dose and urine drug screens during treatment, and treatment completion and days in treatment during the 24-week trial.

Findings: The treatment completion rate was 74% for MET versus 46% for BUP (P < 0.01); the rate among MET participants increased to 80% when the maximum MET dose reached or exceeded 60 mg/day. With BUP, the completion rate increased linearly with higher doses, reaching 60% with doses of 30-32 mg/day. Of those remaining in treatment, positive opioid urine results were significantly lower [odds ratio (OR) = 0.63, 95% confidence interval (CI) = 0.52-0.76, P < 0.01] among BUP relative to MET participants during the first 9 weeks of treatment. Higher medication dose was related to lower opiate use, more so among BUP patients. A Cox proportional hazards model revealed factors associated with dropout: (i) BUP [versus MET, hazard ratio (HR) = 1.61, CI = 1.20-2.15], (ii) lower medication dose (<16 mg for BUP, <60 mg for MET; HR = 3.09, CI = 2.19-4.37), (iii) the interaction of dose and treatment condition (those with higher BUP dose were 1.04 times more likely to drop out than those with lower MET dose, and (iv) being younger, Hispanic and using heroin or other substances during treatment.

Conclusions: Provision of methadone appears to be associated with better retention in treatment for opioid dependence than buprenorphine, as does use of provision of higher doses of both medications. Provision of buprenorphine is associated with lower continued use of illicit opioids.