For the analysis of whether the protective associations of buprenorphine or naltrexone varied based on presence of cooccurring SUD, the primary outcome variable was hospitalizations or ED visits for any nonfatal drug-related poisoning (eTable 1 in the Supplement), derived from the US Center for Disease Control and Prevention listing of ICD-9 and ICD-10 codes pertaining to poisoning and pain.15 Secondary outcomes included opioid and nonopioid poisonings; drug-related poisonings that did not include opioid-specific codes were classified as nonopioid related poisonings.15 The exposure variables were medication use (buprenorphine or naltrexone [oral or ER]), coded as time-varying at the day level. Individuals were permitted to have multiple outcome events as long as they fell within 1 year after the index event. To mitigate misclassification of acute events, we limited place-of-service codes to hospital settings, EDs, ambulances, and inpatient psychiatry facilities, as opposed to long-term care, office-based, and residential facilities. We coded case-days as “1,” encompassing the index event and subsequent events, whereas control-days were coded as “0,” encompassing remaining days in the observation window. Assuming prescription fills denoted consumption of medication, we
