Opioid agonist therapy is the gold standard of care for opioid dependence.
However, the efficacy of treatment may be hindered by concurrent drug use, including
cocaine and benzodiazepines. This thesis examines the impact of concurrent drug use on
treatment retention, and whether it is differentially impacted by geographic region. We
conducted a retrospective cohort study using electronic medical records from 58 opioid
agonist therapy clinics in Ontario. One-year treatment retention was the primary outcome
of interest. Both baseline cocaine and benzodiazepine users experienced decreased
retention rates than non-users. Patients who used concurrent drugs at higher frequencies
experienced decreased retention rates compared to those who used less often. Northern
and urban patients were more likely to be baseline cocaine users, and Southern urban
patients were more likely to be benzodiazepine users. Both baseline and continued
concurrent drug use is predictive of treatment drop out in Northern and Southern patients.
