Evaluation of warfarin initiation regimens in elderly inpatients.
OBJECTIVE
To compare initial warfarin doses of 5 mg or below and doses above 5 mg in hospitalized elderly.


METHODS
Retrospective review of charts identified from computerized pharmacy records.


METHODS
County teaching hospital.


METHODS
Inpatients aged 65 years or older receiving at least three warfarin doses.


METHODS
We measured the time to first international normalized ratio (INR) of 2.0 or greater, bleeding complications, number of warfarin doses held, and vitamin K use.


RESULTS
The average initial low dose (33 patients) was 4.8 +/- 0.8 mg and the average initial high dose (40 patients) was 9.0 +/-1.2 mg. The mean time to first INR of 2.0 or greater was similar, 3.4 and 3.0 days, respectively (p=0.38). The low-dose group had fewer bleeds (7 vs 13, p=0.28) and doses held (11 vs 18 patients, p=0.27, 30 vs 50 doses). Four patients in each group received vitamin K (p=0.8). Forty-four percent of patients with an INR of 4 or above and 48% of patients who had a dose held were on a long-term drug or had a new drug added that could cause a major drug interaction with warfarin.


CONCLUSIONS
In this pilot study, hospitalized elderly who received a low versus high initial dose of warfarin achieved therapeutic INRs in a similar time and had lower but not significantly different safety outcomes.
O'Connell
M B
MB
Department of Experimental and Clinical Pharmacology, College of Pharmacy, University of Minnesota, Minneapolis 55455-0353, USA.
Kowal
P R
PR
Allivato
C J
CJ
Repka
T L
TL
D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced / Q000517:prevention & control; D006490:Hemostatics / Q000627:therapeutic use; D006766:Hospitals, County; D006784:Hospitals, Teaching; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D019637:Orthopedic Procedures; D010865:Pilot Projects; D012189:Retrospective Studies; D014812:Vitamin K / Q000627:therapeutic use; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use*
D000925:Anticoagulants; D006490:Hemostatics; D014812:Vitamin K; D014859:Warfarin