Abstract 1594: Validation of a Common Warfarin Dosing Regimen in the Elderly
Anticoagulation with warfarin is difficult in the elderly, given their sensitivity to the drug and their greater risk of complications. The ACCP has set a series of guidelines on which common warfarin dosing regimens are based. The effectiveness and safety of this regimen in the elderly is unknown.
METHODS We developed a web based program for dosing warfarin based on ACCP recommendations (ADR). From our anticoagulation practice we then identified 27 consecutive patients over the age of 60 (19 male, age=74.7 +/− 8.4 years range 62–90) with chronic atrial fibrillation, who had been on warfarin for at least 1 year and whose medical regimen was otherwise stable. Their INR and clinical histories were then followed prospectively using ADR. These were then compared to the values obtained on a corresponding number of determinations in the months prior ADR adoption (UC) when dosing was based on the discretion of experienced physicians.
RESULTS The patients were followed prospectively for 4.7±1.6 months. Using ADR patients were more often in therapeutic range compared to UC (0.67 vs. 0.52, p<0.05). This appeared to be due to a reduction in time spent in sub therapeutic range (0.19 vs. 0.36, p<0.01). The duration of time spent with a supratherapeutic INR was the same for both groups 0.15 vs. 0.11, p=NS).
CONCLUSION A warfarin dosing regimen based on current ACCP guidelines lead to effective and safer anticoagulation in elderly patients, and is superior to routine care even by a trained physician.