Initiation of warfarin therapy in elderly medical inpatients: a safe and accurate regimen.
OBJECTIVE
Elderly patients are at high risk of over-anticoagulation when treated with warfarin, especially during treatment induction. We developed a simple low-dose regimen for starting warfarin therapy in elderly inpatients. The daily maintenance dosage is predicted from the international normalized ratio (INR) measured the day after the third daily intake of a 4-mg dose. We conducted a prospective multicenter study to evaluate the accuracy and safety of this regimen.


METHODS
We studied 106 elderly (age >or=70 years) inpatients (mean [+/- SD] age, 85 +/- 6 years; range, 71 to 97 years) who had a target INR of 2.0 to 3.0. Accuracy in predicting the daily maintenance dose from INR value on day 3 was evaluated.


RESULTS
The predicted daily maintenance warfarin dose (3.1 +/- 1.6 mg/d) correlated closely with the actual maintenance dose (3.2 +/- 1.7 mg/d; R(2) = 0.84). The predicted dose was equal to the actual dose in 77 patients (73%; 95% confidence interval [CI]: 64% to 81%) and within 1 mg in 101 patients (95%; 95% CI: 91% to 99%). The mean time needed to achieve a therapeutic INR was 6.7 +/- 3.3 days (median, 6.0 days); the mean time needed to achieve the maintenance dose was 9.2 +/- 4.5 days (median, 7.0 days). None of the patients had an INR >4.0 during this period. One fatal bleeding event was recorded in a patient with an INR in the therapeutic range.


CONCLUSIONS
Our warfarin induction regimen was simple, safe, and accurate in predicting the daily maintenance warfarin dose in elderly hospitalized patients.
Siguret
Virginie
V
Hematology Laboratory, Charles Foix Teaching Hospital (AP-HP), Paris, France. virginie.siguret@cfx.ap-hop-paris.fr
Gouin
Isabelle
I
Debray
Matthieu
M
Perret-Guillaume
Christine
C
Boddaert
Jacques
J
Mahé
Isabelle
I
Donval
Valérie
V
Seux
Marie-Laure
ML
Romain-Pilotaz
Marjolaine
M
Gisselbrecht
Mathilde
M
Verny
Marc
M
Pautas
Eric
E
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects* / Q000493:pharmacokinetics / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005544:Forecasting; D006801:Humans; D007297:Inpatients; D008297:Male; D010347:Patient Care Planning; D013927:Thrombosis / Q000517:prevention & control*; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects* / Q000493:pharmacokinetics / Q000627:therapeutic use
D000925:Anticoagulants; D014859:Warfarin