Proportional Hazards Frailty Models for Recurrent Methadone Maintenance Treatment

The authors' objective in this study was to identify determinants of time to discontinuation of methadone maintenance treatment (MMT) across multiple treatment episodes. Population-level data on drug dispensations for all patients receiving methadone for opioid maintenance throughout the tenure of the British Columbia, Canada, methadone program to date (1996-2007) were extracted from an administrative database. Proportional hazards frailty models were developed to assess factors associated with time to discontinuation from recurrent MMT episodes. A total of 17,005 patients experienced 32,656 treatment episodes over the 11-year follow-up period. Age, medical comorbidity, and physician patient load, as well as neighborhood-level socioeconomic status indicators, were significant predictors of time to discontinuation of treatment; treatment adherence and average daily doses up to and above 120 mg per day were also associated with longer treatment episodes. Studies have shown that while successfully retained in MMT, clients decrease their illicit drug use and criminal activity, and their risk of mortality is substantially lower; however, the majority of clients relapse. Many reenter treatment. The primary finding of this study was that patients experiencing multiple treatment episodes tended to stay in treatment for progressively longer periods in later episodes.