title: Effect of oral diuretics on chronic warfarin therapy: a retrospective study.
abstract: BACKGROUND
  Limited clinical documentation is suggestive of a drug interaction between warfarin and diuretics.
  
  
  OBJECTIVE
  To evaluate the effect on international normalized ratio (INR) when a daily oral diuretic is started or increased in patients on chronic stable warfarin therapy.
  
  
  METHODS
  The medical records of all active patients of two hospital-based anticoagulation clinics were retrospectively reviewed to identify patients who were started on or received a dose increase of a daily oral diuretic while on stable warfarin therapy. The primary endpoint was the mean difference between an INR recorded within 30 days prior to the diuretic initiation (pre-INR) and an INR recorded within 30 days after diuretic initiation (post-INR).
  
  
  RESULTS
  A total of 1254 patient charts were screened and a total of 123 patients met the study criteria. The mean difference in pre-INR and post-INR was 0.09 (95% CI -0.03 to 0.21, p = 0.12). Post-INR values were outside of the patient's therapeutic range in 39 patients (32%), but no major bleeding or thromboembolic events were reported.
  
  
  CONCLUSIONS
  Based on this retrospective study, diuretics did not result in a significant change in the INR in patients on stable warfarin therapy.
authors.affiliation: INTEGRIS Baptist Medical Center, Department of Pharmacy, Oklahoma City, OK, USA. Heather-Edwards@ouhsc.edu
authors.forename: Heather D
authors.initials: HD
authors.lastname: Edwards
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Webb
authors.forename: Susan E
authors.initials: SE
authors.lastname: Conway
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D001777:Blood Coagulation / Q000187:drug effects*; D004232:Diuretics / Q000008:administration & dosage* / Q000009:adverse effects; D004347:Drug Interactions; D016903:Drug Monitoring / Q000379:methods; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D009825:Oklahoma; D012189:Retrospective Studies; D013923:Thromboembolism / Q000097:blood / Q000517:prevention & control*; D013997:Time Factors; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D000925:Anticoagulants; D004232:Diuretics; D014859:Warfarin