title: Defining risk of prescription opioid overdose: pharmacy shopping and overlapping prescriptions among long-term opioid users in medicaid.
abstract: Use of multiple pharmacies concurrently (pharmacy shopping) and overlapping prescriptions may be indicators of potential misuse or abuse of prescription opioid medications. To evaluate strategies for identifying patients at high risk, we first compared different definitions of pharmacy shopping and then added the indicator of overlapping opioid prescriptions. We identified a cohort of 90,010 Medicaid enrollees who used ≥ 3 opioid prescriptions for ≥ 90 days during 2008 to 2010 from a multistate Medicaid claims database. We compared the diagnostic odds ratios for opioid overdose events of 9 pharmacy shopping definitions. Within a 90-day interval, a threshold of 4 pharmacies had the highest diagnostic odds ratio and was used to define pharmacy shopping. The overdose rate was higher in the subgroup with overlapping prescriptions (18.5 per 1,000 person-years [PYs]) than in the subgroup with pharmacy shopping as the sole indicator (10.7 per 1,000 PYs). Among the subgroup with both conditions, the overdose rate was 26.3 per 1,000 PYs, compared with 4.3 per 1,000 PYs for those with neither condition. Overlapping opioid prescriptions and pharmacy shopping measures had adjusted hazard ratios of 3.0 and 1.8, respectively, for opioid overdose. Using these measures will improve accurate identification of patients at highest risk of opioid overdose, the first step in implementing targeted prevention policies.
  
  
  CONCLUSIONS
  Long-term prescription opioid use may lead to adverse events, including overdose. Both pharmacy shopping and overlapping opioid prescriptions are associated with adverse outcomes. This study demonstrates that using both indicators will better identify those at high risk of overdose.
authors: Office of the Associate Director for Policy, Centers for Disease Control and Prevention, Atlanta, Georgia. Electronic address: xco2@cdc.gov.
authors: Zhuo
authors: Z
authors: Yang
authors: Departments of Physical Medicine and Rehabilitation, VA Northern California Health Care System, Mather, California, and University of California Davis School of Medicine, Sacramento, California.
authors: Barth
authors: B
authors: Wilsey
authors: National Center for Injury Prevention and Control, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors: Michele
authors: M
authors: Bohm
authors: Center for Healthcare Policy and Research, University of California Davis School of Medicine, Sacramento, California.
authors: Meghan
authors: M
authors: Weyrich
authors: Office of the Associate Director for Policy, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors: Kakoli
authors: K
authors: Roy
authors: Center for Healthcare Policy and Research, University of California Davis School of Medicine, Sacramento, California.
authors: Dominique
authors: D
authors: Ritley
authors: Office of the Commissioner, Food and Drug Administration, Silver Spring, Maryland.
authors: Christopher
authors: C
authors: Jones
authors: Center for Healthcare Policy and Research, University of California Davis School of Medicine, Sacramento, California.
authors: Joy
authors: J
authors: Melnikow
mesh_terms: D000293:Adolescent; D000328:Adult; D000701:Analgesics, Opioid / Q000627:therapeutic use*; D015331:Cohort Studies; D062787:Drug Overdose / Q000453:epidemiology*; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008484:Medicaid / Q000706:statistics & numerical data*; D008875:Middle Aged; D010594:Pharmacies / Q000706:statistics & numerical data*; D000067490:Prescription Drug Overuse / Q000706:statistics & numerical data*; D012307:Risk Factors; D014481:United States; D055815:Young Adult
chemical_list: D000701:Analgesics, Opioid
keywords: Prescription opioids; overdose risk factors; overlapping prescriptions; pharmacy shopping