Retention rate and substance use in methadone and buprenorphine maintenance therapy and predictors of outcome: results from a randomized study

This was a 6-month, randomized, flexible-dose study comparing the effects of methadone (Meth) and buprenorphine (Bup) on retention rate and substance use in a sample of 140 opioid-dependent, primarily heroin-addicted, patients who had been without opioid substitution therapy in the 4 weeks prior to the study. The major aims were to compare the efficacy of Bup and Meth in a flexible dosing regimen and to identify possible predictors of outcome. There were no major inhomogeneities between treatment groups. All patients also received standardized psychosocial interventions. Mean daily dosages after the induction phase were 44-50 mg for Meth and 9-12 mg for Bup. Results from this study indicate a favourable outcome, with an overall retention rate of 52.1% and no significant differences between treatment groups (55.3% vs. 48.4%). Substance use decreased significantly over time in both groups and was non-significantly lower in the Bup group. Predictors of outcome were length of continuous opioid use and age at onset of opioid use, although these were only significant in the Bup group. Mean dosage and other parameters were not significant predictors of outcome. Overall, the results of this study give further evidence that substitution treatment is a safe and effective treatment for drug dependence. Meth and Bup are equally effective. Duration of continuous opioid use and age at onset were found to have predictive value for negative outcome. The intensity of withdrawal symptoms showed the strongest correlation with drop-out. Future studies are warranted to further address patient profiles and outcome under different substitution regimens.