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Completed

NCT Number: NCT00794755

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

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.

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Key information

Conditions

Coagulation Cardiovascular Diseases Embolism and Thrombosis Thrombosis Vascular Diseases

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 3

Primary location

Ottawa Hospital Thrombosis Clinic

Ottawa, Ontario, K1Y4E9, Canada

About this study

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.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Vitamin K1 (Phytonadione)

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

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.

Primary outcomes

  1. 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

    Time frame: At study initiation (for the six month pre-intervention period) and at study completion (after the six-month intervention period)

  2. 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

    Time frame: Monthly

Secondary outcomes

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

    Time frame: Over 6 month study period

  2. Recurrent thrombosis

    Time frame: Over six month study period

Sponsors and collaborators

Lead sponsor

Ottawa Hospital Research Institute

Other

Registry information

Official study 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

Acronym: LOCK

Important dates

Study start
2008
Primary completion
2010
Study completion
2010
First posted
Nov 20, 2008
Registry last updated
Jul 27, 2011

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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