for at least 45 days following the last dose of the most recent prescription assumed to be used. We subsequently limited our sample to 179 280 individuals who had a primary diagnosis of OUD and restricted the years of observation to 2011 to 2016, concomitant with the introduction of ER naltrexone for OUD in 2011 (Figure 1). We conducted retrospective analyses on this sample to evaluate the association between baseline cooccurring SUD, either concurrent with or in the 6-month preceding OUD treatment initiation, and subsequent initiation of buprenorphine or naltrexone during the individual’s first treatment episode. Individuals with history of methadone treatment were not included, as methadone treatment programs are characterized by close patient supervision and frequent drug testing14 that may confound observed associations between medication treatment and outcomes. The diagnosis of OUD was based on ICD-9 and ICD-10 codes (eTable 1 in the Supplement).
