A prospective, randomized trial to compare the time taken to achieve a therapeutic INR upon re-starting warfarin at a "loading" dose (namely 1.5 times the "maintenance" dose for 3 days) compared to the known "maintenance" dose.
Patients will be identified via the University of Alberta Hospital Anticoagulation Management Service. Following the receipt of written, informed consent, patients will be randomized to re-start warfarin at their "maintenance" dose or at a "loading" dose (1.5 times the maintenance dose for 3 days, then resumption of warfarin dosing as per the maintenance dose). Randomization will be performed on-line through the EPICORE Centre. Assuming Day 1 is the day warfarin is re-started, patients will have INRs done on day 3 and at least every 2 days thereafter until a therapeutic INR is obtained. In addition, protein C, protein S and factor II levels will be obtained while the patient is on stable maintenance dosing of warfarin (i.e., prior to holding warfarin for the procedure), 7 days after re-starting warfarin, and 14 days after re-starting warfarin. Complete blood counts (CBCs) will be done with each INR if the patient is taking a low molecular weight heparin (LMWH). Patients will have their anticoagulant therapy managed by the AMS for 6 weeks and will receive a telephone follow-up by the AMS at 90 days to determine if any bleeding or clotting complications occurred.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
39
Patients will be randomized to re-start warfarin at their "maintenance" dose or at a "loading" dose (1.5 times the maintenance dose for 3 days, then resumption of warfarin dosing as per the maintenance dose).
"Maintenance" dose is the amount of warfarin that a patient required to maintain a therapeutic INR.
Univeristy of Alberta
Edmonton, Alberta, Canada
re-starting warfarin "loading" dose vs "maintenance" dose
To compare the time taken to achieve a therapeutic INR between those patients re-starting warfarin with a "loading" dose and a "maintenance" dosing regimen using linear interpolation of INRs.
Time frame: INR drawn 3 days post-reinitiation and then every 2 days until therapeutic
Compare % of time within, above and below the target INR range
To compare the % of time within, above and below the desired INR range between those patients re-starting warfarin with a "loading" dose or "maintenance" dose 6 weeks following restarting warfarin.
Time frame: days
Compare bleeding/clotting complications between two groups
To compare the rates of thrombosis (i.e., stroke) / major hemorrhage between those re-starting warfarin with a "loading" dose or "maintenance" dose at 30 days and 90 days following restarting warfarin.
Time frame: 30 days, 90 days
Compare the levels of protein C, protein S, and factor II between 2 groups.
To compare the levels of protein C, protein S, and factor II between those re-starting warfarin with a "loading" dose or "maintenance" dose.
Time frame: week
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