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

Ottawa Hospital Research Institute

Status and phase

Completed

Phase 3

Conditions

Coagulation

Treatments

Dietary Supplement: Vitamin K1 (Phytonadione)

Dietary Supplement: Placebo

Study type

Interventional

Funder types

Other

Identifiers

NCT00794755

OHREB #2008555-01H

Details and patient eligibility

About

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.

Full 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.

Enrollment

100 estimated patients

Sex

All

Ages

18+ years old

Volunteers

No Healthy Volunteers

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