title: Are brand-name and generic warfarin interchangeable? Multiple n-of-1 randomized, crossover trials.
abstract: BACKGROUND
  Warfarin is a commonly used anticoagulant in North America. Several generic formulations have been approved, raising concern over the safety and efficacy of these products compared with brand-name Coumadin.
  
  
  OBJECTIVE
  To ensure that generic warfarin products can be safely interchanged with Coumadin.
  
  
  METHODS
  Multiple n-of-1 randomized, double-blind, crossover trials switched outpatients (N = 7) between a generic warfarin formulation (Apo-warfarin) and Coumadin over 30 weeks. Study patients took each drug for five 3-week periods, with international normalized ratio (INR) measurements taken twice per period. Inter- and intrapatient differences between generic warfarin and Coumadin were compared, and overall study patient results were compared with those of a Coumadin control group.
  
  
  RESULTS
  There were no differences between warfarin products in terms of mean INR results or number of dosage adjustments required. There also was no difference in INR variation based on warfarin formulation (p > 0.69), nor was a patient and warfarin interaction found (p > 0.81). The INR results were not influenced by whether patients were maintained on Coumadin only (control group) or interchanged between Coumadin and generic warfarin (p = 0.98).
  
  
  CONCLUSIONS
  It appears that patients can safely and effectively switch between generic warfarin and Coumadin.
authors.affiliation: Centre for Evaluation of Medicines, St. Joseph's Healthcare, Hamilton, Ontario, Canada. j.pereira@utoronto.ca
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Pereira
authors.forename: Anne M
authors.initials: AM
authors.lastname: Holbrook
authors.forename: Lisa
authors.initials: L
authors.lastname: Dolovich
authors.forename: Charles
authors.initials: C
authors.lastname: Goldsmith
authors.forename: Lehana
authors.initials: L
authors.lastname: Thabane
authors.forename: James D
authors.initials: JD
authors.lastname: Douketis
authors.forename: Mark A
authors.initials: MA
authors.lastname: Crowther
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Bates
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Ginsberg
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage / Q000592:standards* / Q000627:therapeutic use*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D016568:Drugs, Generic / Q000592:standards / Q000627:therapeutic use; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D013810:Therapeutic Equivalency; D014859:Warfarin / Q000008:administration & dosage / Q000592:standards* / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D016568:Drugs, Generic; D014859:Warfarin