A warfarin induction regimen for out-patient anticoagulation in patients with atrial fibrillation

Br J Haematol. 1998 Jun;101(3):450-4. doi: 10.1046/j.1365-2141.1998.00716.x.

Abstract

Currently available protocols for induction of warfarin anticoagulation employ initial doses of 10 mg and are best suited to in-patient use. However, with the increasing number of elderly patients with atrial fibrillation requiring anticoagulation, there is a need for a less intense regimen which could be used for out-patients. We have established such a regimen and report on its prospective evaluation in 3 7 patients referred for out-patient initiation of warfarin, and a non-randomized comparison with 37 in-patients, with similar diagnoses, commenced on a traditional warfarin protocol. After exclusion of five patients on amiodarone, all of whom experienced supratherapeutic International Normalized Ratio (INR) results, the new out-patient regimen, employing an initial 5 mg dose, resulted in a lower maximum INR during the first 21 d therapy (median 2.9 v 4.0; P = 0.0001) and fewer INRs >4.5 (2/36 v 9/33) compared to the traditional 10 mg regimen. Time to reach stable anticoagulation was similar with each regimen; however, the 5 mg regimen gave a more accurate prediction of maintenance dose (correlation coefficient for predicted versus actual maintenance dose, r = 0.985). In comparison to a traditional 10 mg protocol, the proposed 5 mg warfarin induction regimen proved both safer and more reliable for initiation of prophylactic anticoagulation in patients with atrial fibrillation.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Ambulatory Care / methods*
  • Anticoagulants / administration & dosage*
  • Atrial Fibrillation / drug therapy*
  • Dose-Response Relationship, Drug
  • Drug Administration Schedule
  • Humans
  • International Normalized Ratio
  • Middle Aged
  • Prospective Studies
  • Retrospective Studies
  • Warfarin / administration & dosage*

Substances

  • Anticoagulants
  • Warfarin