AIM: To investigate the real-world effectiveness of pharmacological treatments (buprenorphine, methadone) of opioid use disorder (OUD).

DESIGN: A nation-wide, register-based cohort study in Sweden. Participants were all residents aged 16-64 years living in Sweden using OUD medication from July 2005 to December 2016 (n = 5757, 71.8% men) were identified from registers of prescriptions, inpatient and specialized outpatient care, causes of death, sickness absence and disability pensions.

MEASUREMENTS: Main outcome: hospitalization due to OUD.
SECONDARY OUTCOMES: hospitalization due to any cause; death due to all, natural and external causes. Mortality was analyzed with between-individual multivariate-adjusted Cox hazards regression model. Recurrent outcomes, such as hospitalizations, were analyzed with within-individual analyses to eliminate selection bias. OUD medication use versus non-use was modelled with PRE2DUP (from prescription drug purchases to drug use periods) method.

FINDINGS: Buprenorphine and methadone use were associated with significantly lower risk of OUD hospitalization, but not any-cause hospitalizations, compared with the time-periods when the same individual did not use OUD medication. The use of buprenorphine and methadone were both associated with significantly lower risk of all-cause mortality, compared with non-use of both medications. Similar results were found for risk of mortality due to external causes, but not for mortality due to natural causes. The risk of OUD hospitalization and all-cause mortality was decreased in all duration categories of studied medications, except for methadone use less than 30 days.

CONCLUSIONS: The use of buprenorphine and methadone are both associated with a significantly lower risk of hospitalization due to opioid use disorder and death due to all and external causes, when compared with non-use.