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Maintenance And Monitoring

  • Target INR (International Normalized Ratio) is 2 to 3 for most patients. Children with mechanical/prosthetic mitral valves or recurrent thrombotic events as described above should have a target INR between 2.5-3.5.

  • Discontinue heparin/LMW heparin once the INR is >2 for 2 consecutive days and at least 6 days of heparin/LMW heparin have been given. Anticipate a small decline in INR the following day.

  • INR/PT monitoring recommendations:

    • Obtain baseline before initiating warfarin therapy.

    • Obtain daily INR/PT until therapeutic range has been reached and sustained for 2 consecutive days (loading INR/PT monitoring protocol complete).

    • Obtain INR/PT within 3 days of discharge from the hospital.

    • Obtain INR/PT 5-7 days after initiating a new dose.

    • Once a stable INR between 2-3 (2.5-3.5 for mechanical/prosthetic mitral valves) has been noted on two INRs taken 7 days apart INRs may be obtained weekly. When stable for 4 to 8 weeks, then go to INR every 2-4 weeks.

    • Recommend monitoring at least once a month when stable.

  • Duration of therapy:

    • DVT with an underlying cause: 3 months, with possible extension based on clinical situation; consult Hematology.

    • Idiopathic DVT: 6 -12 months.

    • Mechanical heart valves - indefinite.

    • Recurrent thromboembolic events - indefinite.

    • Antiphospholipid antibody syndrome - indefinite.


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Horton, JD, et al. Warfarin Therapy: Evolving Strategies in Anticoagulation. American Family Physician; 1999 Feb; 59(3):635-646.

Lexi-Drugs Online/Pediatric Lexi-Drugs Online, Warfarin,, Copyright © 1978-2008 Lexi-Comp, Inc, Hudson, OH 44236

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Monagle P. Chan A. Massicotte P. Chalmers E. Michelson AD. Antithrombotic therapy in children: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. [Review] [487 refs] [Guideline. Journal Article. Practice Guideline. Review] Chest. 126(3 Suppl):645S-687S, 2004 Sep.

Roach ES. Golomb MR. Adams R. Biller J. Daniels S. Deveber G. Ferriero D. Jones BV. Kirkham FJ. Scott RM. Smith ER. American Heart Association Stroke Council. Council on Cardiovascular Disease in the Young. Management of stroke in infants and children: a scientific statement from a Special Writing Group of the American Heart Association Stroke Council and the Council on Cardiovascular Disease in the Young. [Journal Article] Stroke. 39(9):2644-91, 2008 Sep.

These guidelines do not establish a standard of care to be followed in every case. It is recognized that each case is different and those individuals involved in providing health care are expected to use their judgment in determining what is in the best interests of the patient based on the circumstances existing at the time. It is impossible to anticipate all possible situations that may exist and to prepare guidelines for each. Accordingly these guidelines should guide care with the understanding that departures from them may be required at times.