Low Dose Supplementation to Improve Anticoagulation Control With Oral Vitamin K as an Adjuvant to Warfarin Therapy

NCT ID: NCT00794755

Last Updated: 2011-07-27

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: PHASE3
• Total Enrollment: 100 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2008-11-30
• Study Completion Date: 2010-04-30

Brief Summary

The main objective of this study is to assess the effectiveness of low dose Vitamin K1 (200 micrograms per day) at improving anticoagulation control in unstable patients on warfarin. This study will also aim to look at effectiveness in the context of genes known to influence warfarin metabolism, variability in the consumption of Vitamin K rich foods, and patient knowledge about warfarin anticoagulation -- factors which have been associated with anticoagulation control and which can influence the effectiveness of this intervention in clinical practice.

Detailed Description

A double-blinded placebo controlled pilot RCT assessing the effectiveness of daily supplementation with low dose Vitamin K1 (200 micrograms per day) against placebo at improving anticoagulation control. Previous studies assessing the efficacy of this intervention have been small and further trials are required to evaluate the true effectiveness and safety profile. Furthermore the impact of genetic polymorphisms, known to impact warfarin metabolism, on the effectiveness/safety of this intervention will also be assessed in this study. Demographic and clinical variables as well as potential confounding variables such as variable dietary Vitamin K intake, concomitant interacting medications, and anticoagulation knowledge will be assessed in this study. Given that this is a pilot study we will be looking at recruitment numbers and necessary parameter estimates to determine the number of patients available at our institution for the study. Power analysis will be performed to evaluate the treatment effect size between the placebo and intervention groups.

Conditions

Coagulation

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: TREATMENT
• Blinding Strategy: TRIPLE

Study Groups

Vitamin K

Group Type: ACTIVE_COMPARATOR

Vitamin K1 (Phytonadione)

Intervention Type: DIETARY_SUPPLEMENT

Vitamin K1 tablets (100 micrograms per tablet) will be taken by patients randomized to the Vitamin K arm. Dosage is two tablets per day (200 micrograms per day) to be taken with warfarin for the 6 month study period.

Placebo

Group Type: PLACEBO_COMPARATOR

Placebo

Intervention Type: DIETARY_SUPPLEMENT

Lactose-based placebo tablets (identical in appearance to the Vitamin K1 tablets) will be taken by patients randomized to the placebo arm. Dosage is two tablets per day to be taken with warfarin for the 6 month study period.

Interventions

Vitamin K1 (Phytonadione)

Vitamin K1 tablets (100 micrograms per tablet) will be taken by patients randomized to the Vitamin K arm. Dosage is two tablets per day (200 micrograms per day) to be taken with warfarin for the 6 month study period.

Intervention Type: DIETARY_SUPPLEMENT

Placebo

Lactose-based placebo tablets (identical in appearance to the Vitamin K1 tablets) will be taken by patients randomized to the placebo arm. Dosage is two tablets per day to be taken with warfarin for the 6 month study period.

Intervention Type: DIETARY_SUPPLEMENT

Eligibility Criteria

Inclusion Criteria

• >= 18 years old
• Have been on warfarin anticoagulation for at least 9 months
• Have an INR target range of 2.0-3.0
• Have "unstable" anticoagulation control, defined as in the preceding 6 months having at least 3 INRs out of range (>= 3.2 or =<1.8) or at least 3 warfarin dose changes
• Have anticoagulation managed by the Ottawa Hospital Thrombosis Clinic
• Able to provide written, informed consent

Exclusion Criteria

• Anticipated interruption or termination of warfarin anticoagulation in the next six months for a period of 1 week or greater
• Patient instability in the preceding six months suspected to be due to a) Interruption of warfarin therapy for a period of 1 week or more or b) Significant non-compliance (assessed from patient record)
• Possess a known allergy to Vitamin K or lactose based placebos
• Unable/Refusal to provide written, informed consent

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

Ottawa Hospital Research Institute

OTHER

Sponsor Role: lead

Responsible Party

Ottawa Hospital Research Institute (OHRI)

Principal Investigators

Philip S Wells, MD, MSc

Role: PRINCIPAL_INVESTIGATOR

Ottawa Hospital, Ottawa Health Research Institute

Locations

Ottawa Hospital Thrombosis Clinic

Ottawa, Ontario, Canada

Countries

Canada

Other Identifiers

OHREB #2008555-01H

Identifier Type: -

Identifier Source: org_study_id