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Warfarin Maintenance Adjustment Calculator

Background:

This program may be useful in an outpatient or inpatient setting to help make adjustments to therapy for patients currently receiving warfarin who are no longer in the therapeutic range at admission or during a clinic visit. The program has pre-programmed warfarin regimens for weekly totals of 5mg all the way up to 105mg. Supra-therapeutic INRs therapeutic interventions are based on the latest ACCP guidelines.

Patient data:

Enter current INR: | Bleeding status:

Enter weekly warfarin total (add up entire week of individual doses): mg

Target INR: (beta: limited to 2-3 during initial release)

Describe current daily dosing regimen - use text only.

E.g. warfarin 5mg daily, except Monday and Friday. Mon and Fri: 7.5 mg
[May leave blank]

Background

Nomogram used by program - Compiled by NewMedicalTerms (2011-2012)

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Warfarin Maintenance Dosing Adjustment Nomogram for INR Goal of 2-3
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Adjustment Guidelines
A: Baseline CBC, PT/INR required prior to continuation of warfarin therapy.
B: Assess patient compliance and determine if any changes have been made that may impact therapy: 1) addition of interacting drugs or herbal products; 2) changes in diet (eating/not eating) 3) changes in health status.
C: Based on the INR results make adjustments to the current therapy based on the ranges below:

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INR < 1.5
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1.) Verify compliance (if non-compliant: resume therapy at previous dose).
2.) If dosage adjustment needed: increase maintenance dose by 5%- 20%*.
[* Some clinicians recommend a 'booster dose' 1.5 to 2x the daily maintenance dose x 1 ]
3.) Return: 3 - 7 days

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INR 1.5 - 1.9
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1.) Verify compliance (if non-compliant: resume therapy at previous dose).
2.) [* Some clinicians recommend a 'booster dose' 1.5 to 2x the daily maintenance dose x 1 ]
3.) If dosage adjustment needed: increase maintenance dose by 5 - 15% (use lower end of this range for INR values close to the therapeutic range).
4.) Return: 3 - 7 days

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INR 2.0 - 3.0
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1.) No Changes Needed
2.) Return: 4 weeks

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INR 3.1 - 3.4
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1.) Dose adjustment usually not necessary if level is at the low end of this range ( 3.1 - 3.2) and at least two previous levels were therapeutic. Recheck in 3 to 7 days.
2.) Consider decreasing dose by 5 - 10% and/or holding one dose.
3.) Recheck in 3- 7 days.

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INR 3.5 - 3.9
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1.) consider holding one dose.
2.) evaluate any clinical changes that may have occurred with the patient (eating regularly, no new medications, etc.)
3.) consider decreasing the maintenance dose by 5 -15% depending on magnitude of the INR elevation.
4.) Return: 1- 3 days.

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INR 4.0 - 4.9 with no significant bleeding
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1.) Hold warfarin until INR is within the therapeutic range.
2.) Recommend lowering maintenance dose by 5%- 20%
3.) Increase frequency of monitoring until problem resolved (daily initially).
4.) (8th ACCP): If only minimally above therapeutic range or associated with a transient causative factor, no dose reduction may be required.

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INR > 5.0
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1.) Review the latest ACCP guidelines - ELEVATED INRs.
2.) Return daily until therapeutic.

Reference:

1] Ansell J, Hirsh J, Hylek E, Jacobson A, Crowther M, Palareti G. Pharmacology and management of the vitamin K antagonists: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. 2008;133:160S-198S.

2] Holbrook A, Schulman S, Witt DM, Vandvik PO, Fish J, Kovacs MJ, Svensson PJ, Veenstra DL, Crowther M, Guyatt GH; American College of Chest Physicians. Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012 Feb;141(2 Suppl):e152S-84S. doi: 10.1378/chest.11-2295.

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