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

Information source: Ottawa Hospital Research Institute
ClinicalTrials.gov processed this data on August 23, 2015
Link to the current ClinicalTrials.gov record.

Condition(s) targeted: Coagulation

Intervention: Vitamin K1 (Phytonadione) (Dietary Supplement); Placebo (Dietary Supplement)

Phase: Phase 3

Status: Completed

Sponsored by: Ottawa Hospital Research Institute

Official(s) and/or principal investigator(s):
Philip S Wells, MD, MSc, Principal Investigator, Affiliation: Ottawa Hospital, Ottawa Health Research Institute


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.

Clinical Details

Official title: A Phase III Pilot RCT (Randomized, Controlled Trial) to Assess the Effectiveness of Low Dose Vitamin K1 (200 Micrograms Per Day) on Improving Anticoagulation Control in Unstable Patients on Warfarin

Study design: Allocation: Randomized, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Investigator, Outcomes Assessor), Primary Purpose: Treatment

Primary outcome:

Anticoagulation control -- Point estimates (and standard deviations) for the following variables: Percent time in therapeutic range, standard deviation of INRs, number of INRs outside of therapeutic range, and number of dose changes

Recruitment Numbers -- Number of patients deemed eligible, Number of patients solicited, Number of patients screened, Number of patients enrolled, and Number of enrolled patients lost to follow-up

Secondary outcome:

Bleeding Events -- Both major and minor as defined by the International Society on Thrombosis and Haemostasis (ISTH) criteria

Recurrent thrombosis

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.


Minimum age: 18 Years. Maximum age: N/A. Gender(s): Both.


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

Locations and Contacts

Ottawa Hospital Thrombosis Clinic, Ottawa, Ontario K1Y4E9, Canada
Additional Information

Starting date: November 2008
Last updated: July 26, 2011

Page last updated: August 23, 2015

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