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Selected warfarin nomograms used by the warfarin dosing program
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The authors make no claims of the accuracy of the information contained herein; and these suggested doses and/or guidelines are not a substitute for clinical judgment. Neither GlobalRPh Inc. nor any other party involved in the preparation of this document shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.    PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.

Standard Warfarin Initiation Nomogram  Printable version

Warfarin initiation nomogram for thrombosis treatment
Target INR (2 - 3)    Based on  Crowther et al.2

INR Dosage
Measure PT/INR on day 1 Obtain  baseline INR 5 mg
Measure PT/INR on day 2 <1.5
1.5 - 1.9
2.0 - 2.5
> 2.5
5 mg
2.5 mg
1 - 2.5 mg
0 mg
Measure PT/INR on day 3 <1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
5 - 10 mg
2.5 - 5 mg
0 - 2.5 mg
0 mg
Measure PT/INR on day 4 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
10 mg
5.0 -7.5 mg
0 - 5 mg
0 mg
Measure PT/INR on day 5 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
10 mg
7.5 - 10 mg
0 - 5 mg
0 mg
Measure PT/INR on day 6 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
7.5 - 12.5 mg
5 - 10 mg
0 - 7.5 mg
0 mg

Warfarin Initiation Nomogram - Low Risk Patient

Warfarin nomogram for low-risk patients based on a slightly modified version of Crowther et al.2 and Kovacs et al.7  5-mg warfarin initiation nomogram.  

Consider a starting dose of 7.5mg to  10 mg.

Low-risk patient definedled: Patient less than 60 years of age with a LOW bleeding risk and no concurrent use of interacting medications. Based on criteria listed in Haines et al.5

INR Dosage
Measure PT/INR on day 1 Obtain  baseline INR 7.5 - 10 mg
Measure PT/INR on day 2 <1.5
1.5 - 1.9
2.0 - 2.5
> 2.5
7.5 - 10 mg
2.5 mg
1 - 2.5 mg
0 mg (omit dose)
Measure PT/INR on day 3 <1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
5 - 10 mg
2.5 - 5 mg
0 - 2.5 mg
0 mg (omit dose)
Measure PT/INR on day 4 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
7.5 - 10.0 mg
5 - 7.5 mg
0 - 5 mg
0 mg (omit dose)
Measure PT/INR on day 5 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
7.5 - 10 mg
7.5 - 10 mg
0 - 5 mg
0 mg (omit dose)
Measure PT/INR on day 6 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
7.5 - 12.5 mg
5.0 - 10.0 mg
0  - 7.5 mg
0 mg (omit dose)

Warfarin Initiation Nomogram - HIGH Risk Patient (2.5 mg)

Warfarin initiation nomogram for thrombosis treatment - 
Target INR (2 - 3) .   Based on a modified version of Crowther et al.2  5mg warfarin initiation nomogram.


Consider a starting dose of 2.5 - 3 mg

HIGH-risk patient definedled: Patients who are at an increased risk of bleeding such as the elderly or patients with CHF/ liver disease / debilitated / recent major surgery / or patients receiving medications known to potentiate the action of warfarin.

2.5 mg Nomogram Derivation

2.5 mg nomogram


Draft

=================================================================
Warfarin Initiation Nomogram - HIGH Risk Patient   (2.5 mg)
=================================================================

Warfarin initiation nomogram for thrombosis treatment - 
Target INR (2 - 3) .   Based on a modified version of Crowther et al. Ref: #2

Consider a starting dose of 2.5 mg

HIGH-risk patient defined: Patients who are at an increased risk of bleeding such as the elderly or patients with CHF/ liver disease / debilitated / recent major surgery / or patients receiving medications known to potentiate the action of warfarin.
==================================
Day 1
-----------------------------------------------------------------------
INR:   Obtain  baseline INR  
Initial Dosage:     2.5 mg

==================================
Day 2
-----------------------------------------------------------------------

INR                     Dosage
--                         2.5 mg

==================================
Day 3
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    2.5 - 6 mg
1.5 - 1.9              1 - 3 mg
2.0 - 2.5              0 - 2 mg
> 3.0                   Omit dose

==================================
Day 4
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    5 - 7.5 mg
1.5 - 1.9              2.5 - 5 mg
2.0 - 2.5              0 - 2.5 mg
> 3.0                  Omit dose

==================================
Day 5
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    5 - 7.5 mg
1.5 - 1.9              2.5 - 6 mg
2.0 - 2.5              0 - 3 mg
> 3.0                   Omit dose
==================================
Day 6
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    3.5 - 7.5 mg
1.5 - 1.9              2.5 - 6 mg
2.0 - 2.5              0 - 5 mg
> 3.0                   Omit dose

Warfarin Initiation Nomogram - HIGH Risk Patient (3 mg)

Warfarin initiation nomogram for thrombosis treatment - 
Target INR (2 - 3) .   Based on a modified version of Crowther et al.2  5mg warfarin initiation nomogram.


Consider a starting dose of 2.5 - 3 mg

HIGH-risk patient definedled: Patients who are at an increased risk of bleeding such as the elderly or patients with CHF/ liver disease / debilitated / recent major surgery / or patients receiving medications known to potentiate the action of warfarin.

3 mg Nomogram Derivation


3mg nomogram

Draft

=================================================================
Warfarin Initiation Nomogram - HIGH Risk Patient   (3 mg)
=================================================================

Warfarin initiation nomogram for thrombosis treatment - 
Target INR (2 - 3) .   Based on a modified version of Crowther et al. Ref: #2

Consider a starting dose of 3 mg

HIGH-risk patient defined: Patients who are at an increased risk of bleeding such as the elderly or patients with CHF/ liver disease / debilitated / recent major surgery / or patients receiving medications known to potentiate the action of warfarin.
==================================
Day 1
-----------------------------------------------------------------------
INR:   Obtain  baseline INR  
Initial Dosage:     3 mg

==================================
Day 2
-----------------------------------------------------------------------

INR                     Dosage
--                        3 mg
==================================
Day 3
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    3 - 7.5 mg
1.5 - 1.9              1 - 3 mg
2.0 - 2.5              0 - 2 mg
> 3.0                   Omit dose

==================================
Day 4
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    5 - 7.5 mg
1.5 - 1.9              3 - 5 mg
2.0 - 2.5              0 - 3 mg
> 3.0                  Omit dose

==================================
Day 5
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    5 - 7.5 mg
1.5 - 1.9              4 - 6 mg
2.0 - 2.5              0 - 4 mg
> 3.0                   Omit dose
==================================
Day 6
-----------------------------------------------------------------------

INR                     Dosage
<1.5                    5 - 7.5 mg
1.5 - 1.9              3 - 6 mg
2.0 - 2.5              0 - 5 mg
> 3.0                   Omit dose

 

Warfarin Initiation Nomogram - Daily INR Monitoring Possible

Warfarin initiation nomogram for thrombosis treatment - 
Target INR (2 - 3).  Based on criteria listed in Haines et al.5
Required monitoring:   Daily PT/INR
Setting: Inpatient
INR Action
(Starting dose should be based on patient age; presence of  interacting medications; and bleeding risk of patient.  E.g. younger patients with a low risk of bleeding may be started on 7.5 to 10mg)
Measure PT/INR on day 1 Obtain baseline INR Start patient on 2.5 to 10 mg depending on risk factors
Measure PT/INR on day 2 <1.5
1.5 - 1.9
2.0 - 2.5
> 2.5
-No dosage change
-Decrease dose 25 - 50 %
-Decrease dose 50 - 75 %
-Hold next dose
Measure PT/INR on day 3 <1.5
1.5 - 1.9
2.0 - 2.5
> 2.5
-Increase dose 0 - 25 %
-No dosage change
-Decrease dose 25 - 50 %
-Decrease dose 50% or hold next dose
Measure PT/INR on day 4 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
-Increase dose 0 - 25 %
-No dosage change or increase 10 - 25%
-Decrease dose 0 - 25 %
-Decrease dose 50% or hold next dose
Measure PT/INR on day 5 < 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
-Increase dose 25%
-Increase dose 0 - 25 %
-No dosage change or decrease 10 - 25%
-Decrease dose 25 - 50 %

Warfarin Initiation Nomogram - Daily Monitoring NOT possible

Warfarin initiation nomogram for thrombosis treatment - 
Target INR (2 - 3).  Based on criteria listed in Haines et al.5
Required monitoring:   Periodic PT/INR (e.g. q3-5 days)
Setting: Outpatient
INR Action
(Starting dose should be based on patient age; presence of  interacting medications; and bleeding risk of patient.  E.g. younger patients with a low risk of bleeding may be started on 5mg)
Measure PT/INR
on day 1
Obtain baseline INR Start patient on 2.5 to 5.0 mg depending on risk factors
Measure PT/INR
on day 3 or 4
<1.5
1.5 - 1.9
2.0 - 2.5
> 2.5
-Increase weekly dose 5 - 25%
-No dosage change
-Decrease weekly dose 25 - 50 %
-Decrease weekly dose 50% or Hold dose
Measure PT/INR
on day 5 - 7
< 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
-Increase weekly dose 10 - 25%
-Increase weekly dose 0 - 25%
-No dosage change
-Decrease weekly dose 10-25% or Hold dose
Measure PT/INR
on day 8 - 10
< 1.5
1.5 - 1.9
2.0 - 3.0
> 3.0
-Increase weekly dose 10 - 25%
-Increase weekly dose 5 - 20%
-No dosage change
-Decrease weekly dose 10-25% or Hold dose
Measure PT/INR
on day 11 - 14
< 1.5
1.4 - 1.9
2.0 - 3.0
> 3.0
-Increase weekly dose 10 - 20%
-No dosage change
-Decrease weekly dose 10 - 20%
-Decrease weekly dose 5 -20% or Hold dose

References:

1. Ansell J, Hirsh J, Hylek E, Jacobson A, et al. Pharmacology and Management of the Vitamin K Antagonists: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. 2008 (suppl 6);133:160s-198s.

2. Crowther MA, Harrison L, Hirsh J. Warfarin: less may be better. Ann Intern Med. 1997;127:332-3.
Crowther et al.  (Comments:  Initial development of a warfarin initiation nomogram for thrombosis treatment.  Provided guidance for dosage adjustments from day#2 through day #6 starting with an initial dose of 5mg on day #1 of therapy).
3. Crowther MA, Ginsberg JB, Kearon C, et al. A Randomized Trial Comparing 5-mg and 10-mg Warfarin Loading Doses. Arch Intern Med. 1999;159:46-8.

4. Crowther MA, Ginsberg JS, Julian J, et al. A comparison of two intensities of warfarin for the prevention of recurrent thrombosis in patients with the antiphospholipid antibody syndrome. N Engl J Med 2003; 349:1133–1138.

5. Haines ST, Zeolla M, Witt DM. Venous thromboembolism. In: DiPiro JT, Talbert RL, Yee GC, et al, eds. Pharmacotherapy: A Pathophysiologic Approach. 6th ed. New York, NY: McGraw-Hill Inc; 2005:373-413.
Haines et al.  (Comments:  Listed two nomograms with common dosage reduction patterns found in other nomograms.   Because the listed dosage modifications are listed as percentages, this type of dosing scheme can be easily manipulated by a computer program to accept any starting dose and then dynamically create a new nomogram based on the initial starting dose.  Further enhancements can be added such as sophisticated rounding methods that generate common warfarin dosages as well as additional guidance based on a few simple web-form inputs. )

6. Harrison L, Johnston M, Massicotte MP, et al. Comparison of 5-mg and 10-mg Loading Doses in Initiation of Warfarin Therapy. Ann Intern Med. 1997;126:133-6.

7. Kovacs MJ, Rodger M, Anderson DR, et al. Comparison of 10-mg and 5-mg Warfarin Initiation Nomograms Together with Low-Molecular-Weight Heparin for Outpatient Treatment of Acute Venous Thromboembolism. Ann Intern Med. 2003;138:714-719.
Kovacs et al.  (Comments:  Modified the 5mg nomogram developed by Crowther et al (1997): The new nomogram started with two initial 5mg doses followed by potential dosage modification on day #3 instead of day #2.   Also developed a10mg warfarin initiation nomogram with mandatory monitoring and potential modification on Day #3 and Day #5 of therapy. )

Disclaimer

All calculations must be confirmed before use. The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgement. Neither GlobalRPh Inc. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.   Read the disclaimer
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