A warfarin induction regimen for out-patient anticoagulation in patients with atrial fibrillation.
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.
Tait
R C
RC
Department of Haematology, Southern General Hospital, Glasgow.
Sefcick
A
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000553:Ambulatory Care / Q000379:methods*; D000925:Anticoagulants / Q000008:administration & dosage*; D001281:Atrial Fibrillation / Q000188:drug therapy*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D006801:Humans; D019934:International Normalized Ratio; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D014859:Warfarin / Q000008:administration & dosage*
D000925:Anticoagulants; D014859:Warfarin