title: Risk of upper gastrointestinal hemorrhage in warfarin users treated with nonselective NSAIDs or COX-2 inhibitors.
abstract: BACKGROUND
  Little is known about the risk of upper gastrointestinal (GI) hemorrhage during the concomitant use of warfarin and selective cyclooxygenase (COX)-2 inhibitors. We examined the association between the concomitant use of warfarin and nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) or selective COX-2 inhibitors in older adults hospitalized for upper GI hemorrhage.
  
  
  METHODS
  This nested case-control analysis of multiple linked health care databases conducted over 1 year identified a cohort of patients in Ontario, Canada, who were older than 66 years and continuously prescribed warfarin. Case patients were those admitted to the hospital with upper GI hemorrhage while taking warfarin. We compared their prescription records prior to hospitalization with those of age- and sex-matched controls who were also receiving warfarin (the control-case ratio was 4:1). Odds ratios (ORs) for the risk of hospitalization for upper GI hemorrhage while concomitantly using warfarin and celecoxib, rofecoxib, or nonselective NSAIDs were determined.
  
  
  RESULTS
  During the study period, we identified 98 821 elderly patients continuously receiving warfarin. Of those, 361 (0.3%) were admitted to the hospital with upper GI hemorrhage. After adjusting for other potential confounders, case patients were significantly more likely to be also taking nonselective NSAIDs (OR, 1.9; 95% confidence interval [CI], 1.4-3.7), celecoxib (OR, 1.7; 95% CI, 1.2-3.6), or rofecoxib (OR, 2.4; 95% CI, 1.7-3.6) prior to hospitalization relative to controls.
  
  
  CONCLUSIONS
  Patients taking warfarin concomitantly with selective COX-2 inhibitors have an increased risk of hospitalization for upper GI hemorrhage. The risk appears similar to that of patients simultaneously taking warfarin and nonselective NSAIDs.
authors.affiliation: University Health Network, University of Toronto, Toronto, Ontario, Canada. Marisa.battistella@uhn.on.ca
authors.forename: Marisa
authors.initials: M
authors.lastname: Battistella
authors.forename: Muhammad M
authors.initials: MM
authors.lastname: Mamdami
authors.forename: David N
authors.initials: DN
authors.lastname: Juurlink
authors.forename: Linda
authors.initials: L
authors.lastname: Rabeneck
authors.forename: Andreas
authors.initials: A
authors.lastname: Laupacis
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects* / Q000627:therapeutic use; D016022:Case-Control Studies; D015331:Cohort Studies; D016861:Cyclooxygenase Inhibitors / Q000009:adverse effects* / Q000627:therapeutic use; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000139:chemically induced* / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D009864:Ontario / Q000453:epidemiology; D011379:Prognosis; D012042:Registries; D018570:Risk Assessment; D017678:Sex Distribution; D014859:Warfarin / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D016861:Cyclooxygenase Inhibitors; D014859:Warfarin