Anticoagulation: a flexible warfarin dosing regimen may be used.

Clinical bottom line (level 4)

  1. Patients may be successfully anticoagulated using a flexible warfarin dosing regimen.
Fennerty et al: British Medical Journal 1984; 288: 1268-1270
Expires June 2002

The study

Case series with ?objective ?blinded outcomes, not adjusted for confounding factors, not validated in an independent set of patients.
Setting: acute hospital, UK

50 patients (aged range 24 to 81 years; mean 52, 58% male) venous thromboembolism
Note:
  • Patients received continuous iv heparin, adjusted so kaolin-cephalin clotting time was 1.5 to 2.5 normal. Warfarin was started on day one, using the following regimen:
    • day 1: INR < 1.4: dose 10 mg
    • day 2: INR<1.8: dose 10 mg
    • day 2: INR 1.8: dose 1.0 mg
    • day 2: INR >1.8: dose 0.5 mg
    • day 3: INR <2.0: dose 10 mg
    • day 3: INR 2.0-2.1: dose 5.0 mg
    • day 3: INR 2.2-2.3: dose 4.5 mg
    • day 3: INR 2.4-2.5: dose 4.0 mg
    • day 3: INR 2.6-2.7: dose 3.5 mg
    • day 3: INR 3.0-3.1: dose 3.0 mg
    • day 3: INR 3.2-3.3: dose 2.5 mg
    • day 3: INR 3.4: dose 2.0 mg
    • day 3: INR 3.5: dose 1.5 mg
    • day 3: INR 3.6-4.0: dose 1.0 mg
    • day 3: INR >4.0: dose 0.0 mg
    • day 4: INR <1.4: dose refer to haematology
    • day 4: INR 1.4: dose 8.0 mg
    • day 4: INR 1.5: dose 7.5 mg
    • day 4: INR 1.6-1.7: dose 7.0 mg
    • day 4: INR 1.8: dose 6.5 mg
    • day 4: INR 1.9: dose 6.0 mg
    • day 4: INR 2.0-2.1: dose 5.5 mg
    • day 4: INR 2.2-2.3: dose 5.0 mg
    • day 4: INR 2.4-2.6: dose 4.5 mg
    • day 4: INR 2.7-3.0: dose 4.0 mg
    • day 4: INR 3.1-3.5: dose 3.5 mg
    • day 4: INR 3.6-4.0: dose 3.0 mg
    • day 4: INR 4.1-4.5: dose- miss one day then 2.0 mg
    • day 4: INR >4.5: dose- miss two days then 1.0 mg
    • day 5: monitor INR daily until in range and stable
    • day 5: INR >4.0: dose 0.0 mg


    • Control Group: (n = 0, analysed):
    Experimental Group: (n = 50, 50 analysed):

    100% followed for 21 days

    The evidence

  • day 3: 52% within therapeutic range; 42% sub therapeutic
  • day 4: 64% within therapeutic range; 30% sub therapeutic
  • day 21: 88% within therapeutic range

    • Comments

    1. how does this compare with guessing (or using a computer)?

    Citation

    1. Fennerty A, Dolben J, Thomas P, et al: Flexible induction dose regimen for warfarin and prediction of maintenance dose. British Medical Journal 1984; 288: 1268-1270
    Search Terms: bibliographic reference
    Contributor: Chris Ball and Clare Wotton, June 2000
    Reviewer:

    Clinical Question.
    Patient venous thromboembolism
    Intervention or Exposure heparin and warfarin
    Outcome dosing regimen of warfarin