title: Assessment of potential drug-drug interactions with a prescription claims database.
abstract: OBJECTIVE
  The prevalence of 25 clinically important potential drug-drug interactions (DDIs) in a population represented by the drug claims database of a pharmacy benefit management company (PBM) was studied.
  
  
  METHODS
  A retrospective cross-sectional analysis of pharmaceutical claims for almost 46 million participants in a PBM was conducted to determine the frequency of 25 DDIs previously identified as clinically important. A DDI was counted when drugs in potentially interacting combinations were dispensed within 30 days of each other during a 25-month period between April 2000 and June 2002.
  
  
  RESULTS
  The number of DDIs ranged from 37 for pimozide and an azole antifungal to 127,684 for warfarin and a nonsteroidal antiinflammatory drug (NSAID). The highest prevalence (278.56 per 100,000 persons) and highest case-exposure rate (242.7 per 1,000 warfarin recipients) occurred with the warfarin-NSAID combination. The combination with the lowest overall prevalence (cyclosporine and a rifamycin, 0.10/100,000) differed from the combination with the lowest case-exposure rate (pimozide and an azole antifungal, 0.028 per 1,000 azole antifungal recipients). Number of cases, prevalence, and case-exposure rates for both sexes generally increased with age. An estimated 374,000 plan participants were exposed to a clinically important DDI during a 25-month period. Between 20% and 46% of prescription drug claims were reversed (canceled) for a medication with a drug interaction when a warning about the interaction was sent to the pharmacy.
  
  
  CONCLUSIONS
  Analysis of prescription claims data from a major PBM found that 374,000 of 46 million plan participants had been exposed to a potential DDI of clinical importance.
authors.affiliation: College of Pharmacy, University of Arizona, 1703 E. Mabel, Tucson, AZ 85721, USA. malone@pharmacy.arizon.edu
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Malone
authors.forename: David S
authors.initials: DS
authors.lastname: Hutchins
authors.forename: Heather
authors.initials: H
authors.lastname: Haupert
authors.forename: Philip
authors.initials: P
authors.lastname: Hansten
authors.forename: Babette
authors.initials: B
authors.lastname: Duncan
authors.forename: Robin C
authors.initials: RC
authors.lastname: Van Bergen
authors.forename: Steve L
authors.initials: SL
authors.lastname: Solomon
authors.forename: Richard B
authors.initials: RB
authors.lastname: Lipton
mesh_terms: D000293:Adolescent; D000328:Adult; D016907:Adverse Drug Reaction Reporting Systems; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D016208:Databases, Factual; D004347:Drug Interactions; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D004363:Drug Utilization; D005260:Female; D006801:Humans; D007356:Insurance, Pharmaceutical Services / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D010594:Pharmacies / Q000706:statistics & numerical data; D014481:United States