Prospective evaluation of a flexible protocol for starting treatment with warfarin and predicting its maintenance dose.
We have evaluated a flexible warfarin dose induction protocol by monitoring its performance in 100 elderly inpatients. The protocol (designed by Fennerty et al., has two aims: (a) to move the prothrombin time (PT) ratio smoothly and quickly into its therapeutic range, and (b) to predict the steady-state warfarin requirement from the PT ratio measured on the fourth treatment day. It proved simple to use and reasonably successful, since after four days, 67/100 patients had achieved a therapeutic level of PT ratio, nine exceeded the therapeutic range, and 24 remained sub-therapeutic, while none had bled due to excessive anticoagulation. Maintenance dose prediction was tested by comparing the predicted and observed maintenance doses in patients within the 'therapeutic range' of PT ratio after various median times of treatment. After ten days, the observed dose was within 1 mg of that predicted in 65/86 patients (76%). This proportion became 57/77 (74%) after 18 days, and 49/79 (62%) after 34 days.
Department of Pharmacy, Repatriation General Hospital, Daw Park, SA.
D G
DG
Cosh
C K
CK
Moritz
K J
KJ
Ashman
R J
RJ
Dally
A S
AS
Gallus
D000368:Aged; D000369:Aged, 80 and over; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011446:Prospective Studies; D011517:Prothrombin Time; D013927:Thrombosis / Q000517:prevention & control; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use
D014859:Warfarin