Impact of treatment for opioid dependence on fatal drug-related poisoning: a national cohort study in England

AIMS: To compare the change in illicit opioid users' risk of fatal drug-related poisoning (DRP) associated with opioid agonist pharmacotherapy (OAP) and psychological support, and investigate the modifying effect of patient characteristics, criminal justice system (CJS) referral, and treatment completion.

DESIGN: National data linkage cohort study of the English National Drug Treatment Monitoring System and the Office for National Statistics national mortality database. Data were analysed using survival methods.

SETTING: All services in England that provide publicly-funded, structured, treatment for illicit opioid users.

PARTICIPANTS: Adults treated for opioid dependence during April 2005 to March 2009: 151,983 individuals; 69% male; median age 32.6 with 442,950 person-years of observation.

MEASUREMENTS: The outcome was fatal DRP occurring during periods in or out of treatment, with adjustment for age, gender, substances used, injecting status, and CJS referral.

FINDINGS: There were 1,499 DRP deaths (3.4 per 1,000 person-years, 95% CI 3.2-3.6). DRP risk increased while patients were not enrolled in any treatment (adjusted hazard ratio [aHR] 1.73, 95% CI 1.55-1.92). Risk when enrolled only in a psychological intervention was double that during OAP (aHR 2.07, 95% CI 1.75-2.46). The increased risk when out of treatment was greater for men (aHR 1.88, 95% CI 1.67-2.12), illicit drug injectors (aHR 2.27, 95% CI 1.97-2.62), and those reporting problematic alcohol use (aHR 2.37, 95% CI 1.90-2.98).

CONCLUSIONS: Patients who received only psychological support for opioid dependence in England appear to be at greater risk of fatal opioid poisoning than those who received opioid agonist pharmacotherapy.