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.
Full Title of Study: “Evaluation of Maintenance Dosing vs Loading Dosing Upon Restarting Warfarin Therapy: A Prospective Randomized Trial.”
- Study Type: Interventional
- Study Design
- Allocation: Randomized
- Intervention Model: Parallel Assignment
- Primary Purpose: Treatment
- Masking: None (Open Label)
- Study Primary Completion Date: August 2012
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.
- Drug: warfarin
- 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).
- Drug: Warfarin
- “Maintenance” dose is the amount of warfarin that a patient required to maintain a therapeutic INR.
Arms, Groups and Cohorts
- Experimental: Loading
- 1.5 times the maintenance dose for 3 days, then resumption of warfarin dosing as per the maintenance dose
- Active Comparator: Maintenance
- Re-start same dose as previously stable on
Clinical Trial Outcome Measures
- re-starting warfarin “loading” dose vs “maintenance” dose
- Time Frame: 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.
- Compare % of time within, above and below the target INR range
- Time Frame: 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
- Time Frame: 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.
- Time Frame: 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.
Participating in This Clinical Trial
- 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
Gender Eligibility: All
Minimum Age: 18 Years
Maximum Age: N/A
Are Healthy Volunteers Accepted: No
- Lead Sponsor
- University of Alberta
- Provider of Information About this Clinical Study
- Principal Investigator: Tammy Bungard, Principal Investigator – University of Alberta
- Overall Official(s)
- Tammy J Bungard, BSP, PharmD, Principal Investigator, Univeristy of Alberta
- Bruce Ritchie, MD, FRCPC, Principal Investigator, University of Alberta
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