Clinical experience with oral versus intravenous vitamin K for warfarin reversal

Reversal of warfarin with plasma accounts for a large amount of fresh-frozen plasma transfused in the United States. The use of vitamin K is an alternate strategy.

Records of vitamin K prescriptions for warfarin reversal were examined and recipients identified where data were available on dosage, route of administration (oral [PO] and intravenous [IV]) and the availability of both pre- and postadministration international normalized ratio(s) (INRs).

A total of 135 administration events were evaluated: 81 PO and 54 IV. The median (range) preadministration INRs were 5.8 (1.9-16.5) versus 5.0 (1.4-16.5; p=0.61) and the median (range) for the postadministration INRs were 2.4 (1.0-10.4) and 2.1 (1.2-8.2; p<0.01) for the PO and IV routes, respectively. The median (range) doses were 2.5(1-10) and 2.0(1-10) mg for PO and IV, respectively (p<0.01). A total of 44% of the IV vitamin K group achieved an INR of 2 or less within 12 hours versus 14% for the PO route (p<0.01). In multilinear regression the preadministration INR (r=0.14, p<0.01) and time after administration (r=-0.05, p<0.01) were independent variables influencing the postadministration INR but the dose administered (r=0.09, p=0.07) was not.

Vitamin K needs to be given IV if urgent partial correction (<12 hr) of warfarin is required. No influence of dose administered in the range 1 to 10 mg on the postadministration INR was observed.