Anticoagulation
Conditions
Keywords
restarting warfarin, time to therapeutic INR
Brief summary
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.
Detailed description
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.
Interventions
DRUGwarfarin
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).
DRUGWarfarin
Maintenance dose is the amount of warfarin that a patient required to maintain a therapeutic INR.
Sponsors
University of Alberta
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* Have 'stable warfarin maintenance dosing' (defined as last 2 INRs within therapeutic range with weekly warfarin dosing not being changed any more than 10%) * Have an INR indicative of not taking any warfarin (INR \<1.4) or confirmation of the patient not taking any warfarin in the past 4 days * Provide written, informed consent
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| re-starting warfarin loading dose vs maintenance dose | INR drawn 3 days post-reinitiation and then every 2 days until therapeutic | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Compare % of time within, above and below the target INR range | days | 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. |
| Compare bleeding/clotting complications between two groups | 30 days, 90 days | 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. |
| Compare the levels of protein C, protein S, and factor II between 2 groups. | week | To compare the levels of protein C, protein S, and factor II between those re-starting warfarin with a loading dose or maintenance dose. |
Countries
Canada
Outcome results
None listed