A Pharmacogenetic Study of Warfarin Dosing, "The COUMA-GEN Study"

Atrial Fibrillation Clinical Trial

Official title: A Controlled Clinical Pharmacogenetic Study of a CYP2C9 Plus VKORC1 Polymorphism-Based Individualized Dosing Algorithm for Warfarin to Increase Efficiency of Achieving Therapeutic Dosing

Status Completed

Clinical Trial Summary

Anticoagulation with warfarin is a common and potentially hazardous therapeutic intervention. It is a leading cause of iatrogenic bleeding events and, hence, of malpractice claims. There are no good alternatives presently for warfarin anticoagulation, and even when alternatives become available (i.e., ximelagatran), cost, labeling, and experience (outcomes-related) issues will continue to favor an extensive and ongoing use of warfarin. If the present study is able to confirm an advantage for a genotype-driven algorithm, in terms of improved efficiency, therapeutic efficacy, and, especially, safety, then a pharmacogenetics approach to warfarin dosing can be recommended as the basis for an Intermountain Health Care (IHC)-wide quality improvement initiative that should improve patient outcomes, reduce resource use (costs of achieving safe and therapeutic anticoagulation), and reduce adverse clinical events. COUMA-GEN is a prospective, randomized study of patients who are to begin chronic warfarin therapy for specific, qualifying clinical reasons (i.e., atrial fibrillation (AF), deep vein thrombosis (DVT), or post-orthopedic surgery prophylaxis). Qualifying patients will be consented and randomized to an individualized, genotype-based warfarin-dosing regimen or to standard care (without knowledge of genotype). In each study arm, a predicted maintenance dose will be determined. All patients will receive a baseline International Normalized Ratio (INR). For patients in all 3 entry strata, a starting dose of warfarin that is twice the assigned daily maintenance dose (according to the specific treatment arm) will be prescribed on the first and second days, and then the dose will revert to the assigned maintenance dose.

Clinical Trial Description

The objectives of this study are to determine

1. whether the pharmacogenetic guided arm can maintain patients a greater time in therapeutic range (TTR - percentage of values in the targeted therapeutic range once a therapeutic INR has been established) without clinical adverse events (i.e., bleeding complications or thromboembolic events),

2. whether the pharmacogenetic guided arm can achieve a higher percentage of therapeutic warfarin levels by days 5 and 8 of therapy (without intervening non-study dose adjustment), and

3. whether the pharmacogenetic guided arm can reduce the need for unplanned dose adjustments and additional INR measurements because of excessive (or insufficient) INR level and clinical adverse events, i.e., bleeding complications or thromboembolic events.

The goal is to achieve >75% TTR in the PG-algorithm arm. Compare proportion of patients reaching therapeutic INR on days 5 and 8 and the subsequent and overall proportion ("time") of INR measurements in therapeutic range (TTR) over 3 months between standard and PG-based arms.

This study will enroll 200 qualifying, consenting patients of either gender, 18 years and above, any ethnicity, with life expectancies > 1 year, beginning on chronic outpatient warfarin therapy for AF, or emergency department/outpatient therapy for spontaneous DVT, or inpatient therapy (and continued for 1 mo) after orthopedic surgery for DVT prevention, or heart failure patients (EF<25% or apical akinesis or left ventricular aneurysm or extensive wall motion abnormality) being started on therapy to reduce the risk of thromboembolism. ;

Study Design

Allocation: Randomized, Endpoint Classification: Pharmacokinetics Study, Intervention Model: Parallel Assignment, Masking: Double-Blind, Primary Purpose: Treatment

Related Conditions & MeSH terms

• Atrial Fibrillation
• Deep Vein Thrombosis
• Pulmonary Embolism
• Venous Thrombosis

• NCT number: NCT00334464
• Study type: Interventional
• Source: Intermountain Health Care, Inc.
• Status: Completed
• Phase: N/A
• Start date: February 2006
• Completion date: November 2007