title: Evaluation of an initiation protocol of 4 mg of warfarin for atrial fibrillation in the outpatient setting.
abstract: OBJECTIVE
  To describe the efficacy and safety of an initiation algorithm for 4 mg of warfarin in ambulatory patients with atrial fibrillation.
  
  
  METHODS
  Prospectively planned retrospective chart review.
  
  
  METHODS
  Centre for Family Medicine Family Health Team in Kitchener, Ont.
  
  
  METHODS
  Ambulatory patients requiring anticoagulation for atrial fibrillation.
  
  
  METHODS
  Patients were prescribed 4 mg of warfarin to be taken once daily for 3 days. An international normalized ratio (INR) measured on the morning of the fourth day was used to predict the maintenance dose of warfarin. Subsequent INR measurements were obtained biweekly until patients reached their actual maintenance dose.
  
  
  METHODS
  Number of INR values greater than or equal to 4.0 before the warfarin maintenance dose was achieved. Secondary outcome measures included thromboembolic and bleeding events, number of days required to reach therapeutic INR, and correlation between predicted and actual warfarin maintenance dose.
  
  
  RESULTS
  Twenty-five patients were included in the study. The average age was 76.0 years (range 56.0 to 89.0), and 17 patients were women. The average CHADS2 (congestive heart failure, hypertension, age ≥ 75 years,diabetes mellitus, and stroke or transient ischemic attack) score was 2.0.Only 1 patient had an INR greater than 4.0 during the study period. The mean time to achieve a therapeutic INR was 11.0 days. The day 4 INR was moderately predictive of the maintenance dose (r2 = 0.47). There were no adverse events that required medical attention during the study period.
  
  
  CONCLUSIONS
  In this pilot study, an initiation algorithm for 4 mg of warfarin was safe and achieved a therapeutic INR within a reasonable time frame in outpatients with atrial fibrillation.
authors.forename: Vikas Srinivasan
authors.initials: VS
authors.lastname: Sridhar
authors.forename: Philemon
authors.initials: P
authors.lastname: Leung
authors.forename: Nicole
authors.initials: N
authors.lastname: Seymour
authors.forename: Jeff
authors.initials: J
authors.lastname: Nagge
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000553:Ambulatory Care / Q000379:methods*; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D001281:Atrial Fibrillation / Q000188:drug therapy*; D002985:Clinical Protocols; D016903:Drug Monitoring; D005194:Family Practice; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D060046:Maintenance Chemotherapy; D008297:Male; D008875:Middle Aged; D049451:Nomograms; D010865:Pilot Projects; D012189:Retrospective Studies; D013997:Time Factors; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects
chemical_list: D000925:Anticoagulants; D014859:Warfarin