Does Prescription Opioid Shopping Increase Overdose Rates in Medicaid Beneficiaries?

Study objective: The link between prescription opioid shopping and overdose events is poorly understood. We test the hypothesis that a history of prescription opioid shopping is associated with increased risk of overdose events. Methods: This is a secondary analysis of a linked claims and controlled substance dispense database. We studied adult Medicaid beneficiaries in 2014 with prescription opioid use in the 6 months before an ambulatory care or emergency department visit with a pain-related diagnosis. The primary outcome was a nonfatal overdose event within 6 months of the cohort entry date. The exposure of interest (opioid shopping) was defined as having opioid prescriptions by different prescribers with greater than or equal to 1-day overlap and filled at 3 or more pharmacies in the 6 months before cohort entry. We used a propensity score to match shoppers with nonshoppers in a 1:1 ratio. We calculated the absolute difference in outcome rates between shoppers and nonshoppers. Results: We studied 66,328 patients, including 2,571 opioid shoppers (3.9%). There were 290 patients (0.4%) in the overall cohort who experienced a nonfatal overdose. In unadjusted analyses, shoppers had higher event rates than nonshoppers (rate difference of 4.4 events per 1,000; 95% confidence interval 0.8 to 7.9). After propensity score matching, there were no outcome differences between shoppers and nonshoppers (rate difference of 0.4 events per 1,000; 95% confidence interval -4.7 to 5.5). These findings were robust to various definitions of opioid shoppers and look-back periods. Conclusion: Prescription opioid shopping is not independently associated with increased risk of overdose events.