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Background Drug overdoses remain a significant public health burden throughout the world. This study assessed the incidence and predictors of non-fatal and fatal drug overdoses among patients with an opioid use, treated for drug use disorders (DUD) at public treatment centers in Denmark. Methods A consecutive cohort of patients (n = 11,199) were tracked from date of first registered enrollment between the year 2000 and 2010 to first registered drug overdose, death or December 31st 2010, whichever occurred first. Competing-risks regression models were fitted to estimate the sub hazard ratios (SHRs) of non-fatal and fatal drug overdoses and confounding risk factors. Results A total of 3186 (28%) patients experienced a non-fatal drug overdose during follow-up, and 572 (6%) died from an overdose. Use of benzodiazepines (SHR: 1.15 95% CI 1.03, 1.28) 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: 1.57 95% CI 1.42, 1.73) and fatal overdoses (SHR: 1.43 95% CI 1.12, 1.82). Conclusions Patients who use opioids remain at risk of overdoses for a long time after discharge from drug treatment. Besides relevant monitoring and psychosocial support in opioid maintenance treatment, there is a need for informing and educating opioid users in risk factors and preventive measures in settings where they are often difficult to access for traditional treatment services.

BACKGROUND: Opioid agonist treatment (OAT) for opioid use disorders may be delivered at treatment clinics or dispensed from pharmacies, however the type of delivery may be associated with different risks and benefits. The aim of the study was to investigate whether dispensing of methadone or buprenorphine at pharmacies during treatment for opioid use disorders was associated with adverse outcomes.METHODS: Retrospective cohort study using a national, linked, population-level data set from Denmark. Patients included were between 18 and 75 years, living in Denmark, and admitted for treatment for opioid use disorders during 2000-2016 (n = 9299). Cox proportional hazards regression was estimated for convictions, non-fatal overdoses, and death, after the first dispensing of either methadone or buprenorphine from a pharmacy after starting treatment.FINDINGS: Of all patients, 68 % had methadone and 31 % had buprenorphine dispensed at a pharmacy. Compared with the time prior to pharmacy dispension, the risk of criminal convictions increased after having methadone dispensed from a pharmacy (adjusted hazard ratio (aHR) = 1.22, 95 % confidence interval (CI) = 1.16-1.28), non-fatal overdoses (aHR = 1.55, CI 1.41-1.71), and all-cause mortality (aHR = 1.54, CI = 1.43-1.76). After having buprenorphine dispensed at a pharmacy, risk of criminal convictions increased (aHR = 1.08, CI = 1.01-1.16) and non-fatal overdoses (aHR = 1.31, CI = 1.18-1.45), but not all-cause mortality (aHR = 1.07, CI = 0.94-1.23).CONCLUSIONS: For almost all outcomes investigated across medication type, the risk of adverse events increased following a switch from clinic dispension to pharmacy dispension of medications in OAT. Medically responsible and safe provision of OAT may often require more clinical follow-up than what is typically provided when medication is dispensed at pharmacies.