The impact of cocaine use in patients enrolled in opioid agonist therapy in Ontario, Canada.

Background: Opioid agonist therapy is the gold standard of care for opioid use disorder; however, the efficacy of this treatment may be hindered by concurrent drug use, including the use of cocaine. This study examines the impact of cocaine use on treatment retention, while accounting for various risk factors, including geographic location, age, gender, and first-month cocaine use.

Methods: We conducted a retrospective cohort study using anonymized electronic medical records from 58 opioid agonist therapy clinics in Ontario between 2011 and 2013. One-year treatment retention was the primary outcome of interest and was measured by differing frequencies of cocaine use - as well as baseline use - with an additional focus on geographic location (Northern Ontario vs. Southern Ontario).

Results: Our cohort consisted of 3835 patients, with the average retention rate of 44%. Baseline cocaine users had a retention rate of 39% and non-users had a retention rate of 46%. Patients who were cocaine-negative on admission benefited from an increased median days retained (302 vs. 212 days). Patients who used cocaine at higher frequencies had decreased retention rates compared to those who used less often. Despite increased levels of cocaine use, Northern patients were better retained than Southern patients.

Conclusion: Northern patients and patients from urban communities are more likely to be baseline cocaine users. Both baseline and continued cocaine use is predictive of treatment dropout in Northern and Southern patients. The higher the frequency of cocaine use, the more likely a patient is to terminate treatment. Patients in Northern Ontario are retained in treatment at higher rates than their Southern counterparts.