Exposure to opioids was captured using prescription information available in the pharmacy claims (e.g., medication name, fill date, days supplied). Opioid exposure was examined at monthly intervals from each person’s study entry date to their drop in health plan enrollment or end of study period, whichever came first. Individuals were included in the analysis per month if they had enrollment for that entire month. Opioid exposure was determined by an outpatient pharmacy fill for a product containing hydrocodone, oxycodone, tramadol, codeine, morphine, fentanyl, and “other”, which included hydromorphone, buprenorphine, propoxyphene, oxymorphone, methadone, dihydrocodeine, levorphanol tartrate, meperidine hydrochloride, opium, pentazocine, and tapentadol.
The timing of opioid exposure was based on the date of prescription and number of days supplied, which allowed for the determination of monthly exposure as binary (yes/no) and number of days supplied. To standardize the number of days supplied per month, the proportion of each month exposed was calculated as the days supplied divided by the number of days in that month. This study did not standardize doses across opioid types (e.g., oral morphine equivalents) given the variability in suggested conversion factors [24 (link)]. Further, it is unknown if the proportion of opioid prescriptions by type differs for adults with and without CP, and how variation in conversion factors could impact interpretations. Therefore, this study focused on measures of opioid exposure as exposed/not exposed, the number of days supplied, and the proportion of opioid prescriptions by type.
The timing of opioid exposure was based on the date of prescription and number of days supplied, which allowed for the determination of monthly exposure as binary (yes/no) and number of days supplied. To standardize the number of days supplied per month, the proportion of each month exposed was calculated as the days supplied divided by the number of days in that month. This study did not standardize doses across opioid types (e.g., oral morphine equivalents) given the variability in suggested conversion factors [24 (link)]. Further, it is unknown if the proportion of opioid prescriptions by type differs for adults with and without CP, and how variation in conversion factors could impact interpretations. Therefore, this study focused on measures of opioid exposure as exposed/not exposed, the number of days supplied, and the proportion of opioid prescriptions by type.
