Incidence and predictors of drug overdoses among a cohort of patients treated for substance use disorder

Background: Drug overdoses remain a significant public health burden throughout the world. The present study assessed the incidence and predictors of non-fatal and fatal drug overdoses among patients treated for substance use disorders at public outpatient treatment centers in Denmark.

Methods: A consecutive cohort of patients (n = 11,199) were tracked from date of first registered enrollment in substance abuse treatment between the year 2000 and 2010 to first registered drug overdose, death or December 2010, whichever occurred first. Competing-risks regression models were fitted to estimate the sub hazard ratios (HRs) of non-fatal and fatal drug overdoses and confounding risk factors.

Results: A total of 4,042 patients experienced a drug overdose during follow-up, of which 572 patients were fatal. Use of Benzodiazepines (SHR: 95% CI 1.16-1.35) was significantly associated with non-fatal overdose. Intravenous drug use and previous hospitalization for a non-fatal overdose increased the risk of later non-fatal (SHR: 95% CI 1.96-2.38), and fatal overdoses (SHR: 95 % CI 1.12-1.82).

Conclusions: Patients who use opioids remain at risk of overdoses for a long time after discharge from substance abuse treatment. Prescription of methadone and benzodiazepines with insufficient monitoring measures and psychosocial support may be counterproductive and even put patients at risk.