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Use of Phytonadione to Reduce International Normalized Ratio (INR) Variability in Patients on Long-term Warfarin Therapy

This study has been completed.
Information provided by (Responsible Party):
To-Nga Huynh, PharmD., James A. Haley Veterans Administration Hospital Identifier:
First received: November 15, 2011
Last updated: March 7, 2017
Last verified: March 2017

Background: Warfarin is used as an anti-coagulant in patients at risk of developing thrombosis. It has a narrow therapeutic index necessitating close monitoring of International Normalized Ratio (INR). According to a meta-analysis, patients were in therapeutic range only 63.6% of the time. This increases the risk of bleeding or thrombosis. Various retrospective and prospective studies have looked at supplementation with phytonadione in these patients to reduce the variability of INR showing an improvement in variability. Most of these studies have only been done in a small number of patients already on warfarin therapy. This study will focus on patients newly starting warfarin therapy.

Methods: This study is a prospective, randomized, controlled trial performed at James A. Haley Veterans' Hospital (JAHVA). Patients who meet criteria and sign informed consent will receive either phytonadione with warfarin or warfarin alone. Based on a power calculation for 80%, a total of 370 patients will be enrolled (185 participants in each arm). Participants will be randomized to either intervention or control. Intervention group participants will be prescribed their usual starting dose of warfarin along with 200 mcg phytonadione by mouth daily. Control group participants will be prescribed their usual starting dose of warfarin. Both groups will follow the usual standard of care. They will come in for a follow-up INR and warfarin dose titration at least once per week until therapeutic, and then as instructed up to every 6 weeks thereafter. Both groups will participate in anticoagulation clinic activities that constitute the current standard of care. Intervention will last for a total of 6 months for each participant once enrolled.

Hypothesis:Participants in the intervention group being supplemented with 200mcg of phytonadione will spend more total time with a therapeutic INR than participants in the control group.

Condition Intervention
Coagulation Delay
Dietary Supplement: phytonadione

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: No masking
Primary Purpose: Treatment
Official Title: Use of Phytonadione to Reduce INR Variability in Patients on Long-term Warfarin Therapy

Resource links provided by NLM:

Further study details as provided by James A. Haley Veterans Administration Hospital:

Primary Outcome Measures:
  • The primary outcome of this study is to determine the length of time in therapeutic INR range for patients given phytonadione and warfarin compared to warfarin alone [ Time Frame: 6 months ]

Secondary Outcome Measures:
  • Secondary outcomes include the number of adverse events in the form of bleeding or thrombosis for both groups. [ Time Frame: 6 months ]

Enrollment: 370
Study Start Date: September 2011
Study Completion Date: November 2015
Primary Completion Date: November 2015 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Placebo Comparator: Control group
The control group only receiving warfarin therapy (individualized therapy, hence no specific form, dosage, frequency and duration is applicable here - i.e. 5mg daily everyday for 6 months may be applicable to one patient but not all researched patients).
Dietary Supplement: phytonadione
Phytonadione 200mcg PO daily for 6 months + normal dose of warfarin and standard of care treatment
Other Names:
  • Vitamin K
  • Coumadin
Experimental: Phytonadione
Patients receiving 200mcg of phytonadione.
Dietary Supplement: phytonadione
Phytonadione 200mcg PO daily for 6 months + normal dose of warfarin and standard of care treatment
Other Names:
  • Vitamin K
  • Coumadin

Detailed Description:
See above.

Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Be eighteen years of age and older
  • Have a long-term indication for warfarin (will need to be on warfarin for 6 months or longer)
  • Be a new patient on warfarin therapy, or a patient previously on warfarin therapy who has been taken off therapy for more than 2 weeks and needs to be titrated again
  • Anticipate receiving medical care at the study site for the duration of the study
  • Have transportation to and from the JAHVA
  • Have read and signed the Informed Consent document after the study has been fully explained and has had all questions answered

Exclusion Criteria:

  • Have liver or kidney failure
  • Are on hemodialysis or peritoneal dialysis
  • Are pregnant or planning to become pregnant
  • Have Alzheimer's disease, cognitive impairment, or visual impairment
  • Are not compliant with medications
  • Are participating in another study
  • Have scheduled surgery or are planning to undergo major surgery
  • Cannot be reached by telephone
  • Take over-the-counter vitamin K supplementation except multivitamins
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Please refer to this study by its identifier: NCT01474460

United States, Florida
James A. Haley VA Hospital
Tampa, Florida, United States, 33612
Sponsors and Collaborators
James A. Haley Veterans Administration Hospital
Principal Investigator: To-Nga Huynh, PharmD James A. Haley VA Hospital
  More Information

Responsible Party: To-Nga Huynh, PharmD., Anticoagulation Clinical Pharmacist, James A. Haley Veterans Administration Hospital Identifier: NCT01474460     History of Changes
Other Study ID Numbers: Pro00000493
Study First Received: November 15, 2011
Last Updated: March 7, 2017
Individual Participant Data  
Plan to Share IPD: No

Keywords provided by James A. Haley Veterans Administration Hospital:

Additional relevant MeSH terms:
Vitamin K 1
Antifibrinolytic Agents
Fibrin Modulating Agents
Molecular Mechanisms of Pharmacological Action
Growth Substances
Physiological Effects of Drugs processed this record on May 23, 2017