Our primary exposure variable was OUD medication by days, operationalized as days characterized by the presence or absence of prescription coverage or procedure codes for buprenorphine, methadone, or naltrexone (oral or extended-release). Specific national drug codes (buprenorphine and oral naltrexone) and procedure codes (methadone and extended-release naltrexone) can be found elsewhere.20 We assumed that the prescription was filled on the date after the prescription was received by the pharmacy and taken until the last day supplied. We assumed that extended-release naltrexone was active for 28 days from the date of injection.
