A Comparison Study of Oral Anticoagulants (blood thinners) for Extended VEnous Thromboembolism (blood clot in vein)
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Age: 18 years or older
Healthy Volunteers: No
Keywords: VEnous Thromboembolism, anticoagulants, blood thinners, blood clot
Type: Drug study, Phase 3
50 Participants
Venous thromboembolism (VTE) is a condition involving blood clots forming in the veins. When a clot forms in in a deep vein (usually in the leg) it is called a deep vein thrombosis (DVT). When a clot breaks loose and travels to the lungs it is called a pulmonary embolism (PE). VTE is a common, potentially fatal, yet treatable condition.

The standard therapy for all patients with VTE is anticoagulation for 3-6 months.

The most common oral anticoagulants used are:
- vitamin K antagonists (for example, warfarin)
- direct oral anticoagulants (for example, apixaban and rivaroxaban).

VTE that is not associated with any specific event is referred as an ‘unprovoked’ VTE. This can occur after surgery or following long plane flights. In these cases, continuing anticoagulation indefinitely after the initial treatment period is recommended.

The purpose of the COVET study is to determine whether the direct oral anticoagulants, apixaban and rivaroxaban are safer than warfarin. We hope to see fewer bleeding complications with no increase in recurrent blood clots, compared to warfarin.

All three of the anticoagulant agents included in this study (rivaroxaban, apixaban, and warfarin) are FDA approved. Theyx have been shown to be effective in the prevention of recurrent VTE. There have been no studies that have compared these three blood thinners for the purpose of preventing recurrent blood clots long-term.
This study requires

If eligible, you will be randomly assigned (like drawing straws or flipping a coin) to either receive warfarin (target INR of 2-3), apixaban (2.5mg twice daily) or rivaroxaban (20mg daily). Participants should start on the assigned study drug within one week of randomization. Participants on once daily medications will have flexibility in determining the daily dosing timing. You will receive a prescription for the medication you are assigned to.

The following test and procedures will be performed for this study: • At the Screening/Randomization visit (Visit 1) o Review and sign the Informed Consent Document o Physical exam including vital signs o A review of medication(s) you have taken and are currently taking to treat your DVT/PE

• At the Follow-up phone Visits (Month 1, Month 6 and Month 12) o You will be contacted by the Duke Clinical Research Institute (DCRI) Call Center to talk with you about the following:  A review of medication(s) you have taken and are currently taking since the previous visit  Review of information on specific events you may have experienced

• INR level checks • Your INR level will be routinely checked as part of standard care (weekly or monthly) based on your study doctor’s assessment of how stable you are.

Who can participate

Inclusion criteria:

  • Have confirmed acute, symptomatic and unprovoked DVT/PE.
  • Have completed an initial treatment course of oral anticoagulant therapy for 3-12 months.
  • At high risk for recurrent venous thromboembolism after completion of the initial treatment course.
  • Have the capacity to understand and sign an informed consent form.
  • Be 18 years of age and older.
  • Under the direct care of a physician for treatment of VTE for the length of time in the study.

Exclusion criteria:

  • creatinine clearance (CrCl) < 30 mL/min as determined by Cockcroft-Gault formula
  • significant liver disease (Child-Pugh B or C)
  • concomitant use of medications that are strong P-glycoprotein or CYP3A4 inducers/inhibitors
  • life expectancy < 3 months
  • Currently pregnant or breast feeding
  • Active Cancer defined as:
  • Diagnosed with cancer within the past 6 months; or
  • Recurrent, regionally advanced or metastatic disease;
  • Currently receiving treatment or have received any treatment for cancer during the 6 months prior to randomization; or
  • A hematologic malignancy not in complete remission
  • Unwilling/ unlikely to agree to follow up
Benefits and risks of participating

We cannot promise any benefits to you as a result of taking part in this research study.


The study doctor will discuss the risks associated with taking part in this research study.
The study will help cover some of the cost of any co-payments that may be required. This is for two (2) of the study drugs (if randomized or assigned to either warfarin or rivaroxaban). The study will provide co-pay assistance cards through a third party vendor called RxSolutions. Take this card to any pharmacy with your prescription and have the co-pay assistance applied to the cost.
Study duration and period
You will be in this study for 12 months from your screening/ randomization visit.
Recruitment period
From June 22, 2018
UC Davis Medical Center
2315 Stockton Boulevard
Sacramento, CA 95817
Elizabeth Guy
Research Topic
  • Venous Thromboembolism

Have any questions or want to learn more? Leave your contact details below and the research team will reach out to you.


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