Guidelines For Warfarin Management In The Community

Summary

Guidelines for warfarin management in
the community
January 2016
Disclaimer
This guideline has been prepared to promote and facilitate standardisation and consistency
of practice, using a multidisciplinary approach

Information in this guideline is current at time of publication

Queensland Health and the Royal Flying Doctor Service do not accept liability to any person
for loss or damage incurred as a result of reliance upon the material contained in this
guideline

Clinical material offered in this guideline does not replace or remove clinical judgement or the
professional care and duty necessary for each specific patient case

Clinical care carried out in accordance with this guideline should be provided within the
context of locally available resources and expertise

This Guideline does not address all elements of standard practice and assumes that
individual clinicians have the responsibility to:
 Discuss care with consumers in an environment that is culturally appropriate and which
enables respectful confidential discussion. This includes the use of interpreter services
where necessary

 Advise consumers of their choice and ensure informed consent is obtained

 Provide care within scope of practice, meet all legislative requirements and maintain
standards of professional conduct

 Apply standard precautions and additional precautions as necessary, when delivering
care

 Document all care in accordance with mandatory and local requirements

Guidelines for Warfarin Management in the Community
Published by the State of Queensland (Queensland Health) and the Royal Flying
Doctor Service Queensland Section, May, 2016
© State of Queensland (Queensland Health) 2016
This work is licensed under a Creative Commons Attribution Non-Commercial Share
Alike 3.0 Australia licence. In essence, you are free to copy, communicate and adapt
the work for non-commercial purposes, as long as you attribute Medicines Regulation
and Quality, Queensland Health and the Royal Flying Doctor Service, Queensland
Sector, you distribute any derivative work only under this licence and you abide by the
licence terms. To view a copy of this licence, visit
http://creativecommons.org/licenses/by-nc-sa/3.0/au/deed.en
For more information contact:
Medicines Regulation and Quality, Department of Health, GPO Box 48, Brisbane QLD
4001, email [email protected], phone (07)3328 9818

Disclaimer:
The content presented in this publication is distributed by the Queensland Government as an information source only

The State of Queensland makes no statements, representations or warranties about the accuracy, completeness or
reliability of any information contained in this publication. The State of Queensland disclaims all responsibility and all
liability (including without limitation for liability in negligence) for all expenses, losses, damages and costs you might
incur as a result of the information being inaccurate or incomplete in any way, and for any reason reliance was placed
on such information

Guidelines for warfarin management in the community - ii -
Contents
Guidelines for warfarin management in the community ...................................... 1
Purpose ............................................................................................................... 1
Scope .................................................................................................................. 1
Related documents .............................................................................................. 1
Authorising Policy and Standard/s: ............................................................. 1
Procedures, Guidelines and Protocols: ....................................................... 1
Forms and templates: ................................................................................. 1
Other: ......................................................................................................... 1
1. Guideline .................................................................................................... 2
1.1 General information .................................................................................... 2
1.2 Indications .................................................................................................. 2
1.3 Risk assessment ........................................................................................ 3
1.3.1 Risk of stroke in patients with atrial fibrillation .................................... 3
1.3.2 Risk of bleeding ................................................................................. 4
1.3.3 Contraindications to warfarin therapy................................................. 5
1.4 Initiation of warfarin..................................................................................... 6
1.4.1 Patients at low risk of thrombosis (i.e. AF) ......................................... 6
1.4.2 Patients at high risk of thrombosis (e.g. DVT) .................................... 7
1.5 Subsequent maintenance dosing using warfarin ......................................... 8
1.6 Frequency of INR monitoring .................................................................... 10
1.6.1 Patients at low risk of thrombosis (i.e. AF) ....................................... 10
1.6.2 Patients at high risk of thrombosis (e.g. DVT) .................................. 11
1.7 Management of high INR .......................................................................... 11
1.8 Perioperative thromboembolism risk stratification ..................................... 13
1.9 Stopping warfarin for procedures .............................................................. 13
1.10 Factors that influence the INR .................................................................. 15
1.11 Patient counselling ................................................................................... 18
1.12 Auditing management of warfarin ............................................................. 19
1.13 Guide for patients non-responsive to warfarin therapy .............................. 19
2. Review ..................................................................................................... 20
3. Business Area Contact ............................................................................ 20
4. Glossary of terms used in the policy and supporting documents ............. 21
5. Approval and Implementation .................................................................. 21
6. Version Control ........................................................................................ 22
7. References............................................................................................... 22
Guidelines for warfarin management in the community - iii -
Guidelines for warfarin management in the
community
Purpose
This guideline provides recommendations regarding best practice for initiation and
management of warfarin for patients in the community, as well as primary and
community health services (e.g. Home Based Acute Care Service or Hospital in the
Home). This guideline applies to all Queensland Health patients prescribed warfarin in
the community where a work unit procedure is unavailable

Scope
This guideline provides information for all Queensland Health employees (permanent,
temporary and casual) and all organisations and individuals acting as its agents
(including Visiting Medical Officers, Royal Flying Doctor Service and other partners,
contractors, consultants and volunteers)

Related documents
Authorising Policy and Standard/s:
 Queensland Health List of Approved Medicines
Procedures, Guidelines and Protocols:
 Queensland Health inpatient Guidelines for Anticoagulation using Warfarin – Adult
(available from Medicines Regulation and Quality, Department of Health,
Queensland Health, email: [email protected])
Forms and templates:
 Queensland Health Non-Inpatient Rural and Remote Warfarin Record, SW032,
Material number (FAMMIS): 10202082
Other:
 Warfarin patient education booklet (e.g. medication manufacturing company, private
pathology or other)
Guidelines for warfarin management in the community -1-
1. Guideline
1.1 General information
Warfarin inhibits the synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) and
the antithrombotic factors, protein C and protein S. The suppression of proteins C and
S can create a hypercoagulable state in the first few days of warfarin treatment,
especially at doses for conditions with high risk of thrombosis (see section 1.4.2)
(Clarke et al. 2006). In patients at high risk of thrombosis, such as venous
thromboembolism, another anticoagulant (e.g. heparin) is required to provide adequate
anticoagulation cover for the first five days of warfarin initiation therapy

Warfarin is extensively metabolised by the liver, mostly to inactive hydroxylate
metabolites which are predominantly eliminated by the renal system (Micromedex 2.0
2015). For factors that may impact on the metabolism of warfarin or monitoring of the
INR refer to section 1.9 Factors that Influence the INR

The two brands of warfarin available in Australia, Marevan® and Coumadin®, are not
interchangeable and swapping brands may affect INR control. Queensland Health
facilities generally use the Marevan® brand

1.2 Indications
Duration of treatment and target INR may vary depending on the indication for warfarin
therapy (see Table 1 below)

Table 1 Indications for warfarin therapy with recommendations for target INR and
duration
Indication Target INR Minimum recommended
range duration
Valve repairs 2–3 6 weeks post operatively
Bioprosthetic valve
DVT 2–3 3 months
PE
AF*
Irreversible, clinically hyper-coagulable 2–3 Life long, balanced against risks
states
#
Mechanical AVR with no risk factors
High risk mechanical heart valves
Mechanical MVR 2.5 – 3.5 Life long, balanced against risks
#
Mechanical AVR with risk factors
Source: Tran et al. 2013, Guyatt et al. 2012; Kearon et al. 2012; Cardiovascular Expert Group 2012;
Ageno et al. 2012; Keeling et al. 2011
* Refer also to section 1.3.1 Risk of stroke in patients with AF
#
Risk factors: AF, previous VTE, hypercoagulable state, left ventricular dysfunction or older generation
AVR
Risk of bleeding increases if warfarin is combined with antiplatelet therapy. If
considering combination with antiplatelet therapy, discuss options with a specialist. Do
Guidelines for warfarin management in the community -2-
not add aspirin for patients who have both AF and ischaemic heart disease. Consider
addition of clopidogrel to patients with stents after discussion with a specialist (Blaauw
& Crijns 2008). Literature suggests that triple therapy with warfarin, aspirin and
clopidogrel is acceptable for short term treatment of up to four weeks in patients with
acute coronary syndrome and AF (Camm et al. 2010)

1.3 Risk assessment
1.3.1 Risk of stroke in patients with atrial fibrillation
The CHADS2 scoring system (Gage et al. 2001) is a simple system that can be used to
assess the annual risk of stroke in AF. In the CHADS2 scoring system (see Table 2)
each point increases the annual risk of stroke by a factor of 1.5. Treatment with
warfarin is recommended for a CHADS2 or CHA2DS2VASc scores of equal to or
greater than 2. Whilst the CHADS2 score is simple it does not include many common
stroke risk factors. The CHA2DS2VASc score (see Table 3) is inclusive of the most
common stroke risk factors in everyday clinical practice and has been validated in
multiple cohorts; the accumulated evidence shows that CHA2DS2VASc is better at
identifying ‘truly low-risk’ patients with AF and is as good as, and possibly better than,
scores such as CHADS2 in identifying patients who develop stroke and
thromboembolism (ESC Guidelines 2012)

Table 2 CHADS2 scoring system
CHADS2 Clinical Add CHADS2 score Annual risk of
characteristic points Stroke
C Congestive Heart Failure 1 0 1.9%
H History of Hypertension 1 1 2.8%
A Age 75 years or older 1 2 4%
D Diabetes Mellitus 1 3 5.9%
S2 History of Stroke or 2 4 8.5%
Transient Ischaemic
5 12.5%
Attack
TOTAL SCORE (max 6) = 6 18.2%
Source: Gage et al. 2001
Guidelines for warfarin management in the community -3-
Table 3 CHA2DS2VASc scoring system
CHA2DS2VASc Clinical Add CHA2DS2VASc score Annual risk of
characteristic points Stroke
C Congestive Heart Failure 1 0 0%
H History of Hypertension 1 1 1.3%
A Age 75 years or older 2 2 2.2%
D Diabetes Mellitus 1 3 3.2%
S2 History of Stroke or 2 4 4.0%
Transient Ischaemic
5 6.7%
Attack
V Vascular disease 1 6 9.8%
A Age 65 years or older 1 7 9.6%
Sc Sex category, female 1 8 6.7%
TOTAL SCORE (max 9) 9 15.2%
=
Source: ESC Guidelines for the management of atrial fibrillation European Heart Journal (2012)
Direct comparison between the effects of Vitamin K Antagonist (VKA) and aspirin has
been undertaken in nine studies, demonstrating that VKA were significantly superior,
with an RR reduction of 39%

1.3.2 Risk of bleeding
The risk of stroke should be weighed against the risk of bleeding to assess
appropriateness of anticoagulant therapy. Warfarin causes major bleeding in one to
two per cent of people treated and intracranial bleeding in 0.1 to 0.5 per cent of
patients each year of treatment (Gallus et al. 2000). The highest rate of major bleeding
occurs in the first three months of treatment (Clarke et al. 2006). In comparison, aspirin
causes major bleeding in 1.3 per cent of patients (van Walraven et al. 2002). Absolute
risk increase for intracranial haemorrhage with warfarin compared to aspirin is only 0.2
per cent per year (Hart et al. 2007)

Risk of bleeding can be assessed using the HAS-BLED scoring system (see Table 4)
where a bleeding risk score of equal to or greater than 3 indicates high risk. There are
other bleeding risk assessment tools available including HEMORR2HAGES (Gage et
al. 2006). Assessment may identify reversible risks that can be managed prior to
initiation of warfarin. In general, clinicians should be cautious and conduct regular
review of the patient if initiating warfarin (Camm et al. 2010)

Guidelines for warfarin management in the community -4-
Table 4 HAS-BLED scoring system
HAS-BLED Clinical characteristic Add points
H Hypertension 1
(uncontrolled, greater than 160 mm Hg systolic)
A Abnormal renal and liver function (1 point each) 1 or 2
S Stroke (previous history, particularly lacunar) 1
B Bleeding (history or predisposition e.g. anaemia) 1
L Labile International INRs 1
(i.e. time in therapeutic range is less than 60 per cent)
E Elderly (older than 65 years) 1
D Drugs (e.g. non-steroidal anti-inflammatory or antiplatelet drugs, 1 or 2
heparin or thrombolysis) OR alcohol (1 point each)
TOTAL SCORE (out of maximum 9 points) =
Source: Pisters et al. 2010
HAS-BLED scores of 0, 1 or 2 correlate to 1.13, 1.02 and 1.88 major bleeds per 100
patient-years respectively. This risk significantly increases at higher scores with HAS-
BLED scores of 3, 4 and 5 correlating to 3.74, 8.70 and 12.50 major bleeds per 100
patient-years respectively (Pisters et al. 2010)

1.3.3 Contraindications to warfarin therapy
In determining whether to start warfarin, there is a need to consider absolute and
relative contraindications. The lists below are not exhaustive (Smith 2011)

Absolute contraindications to warfarin therapy include:
 known large oesophageal varices
 significant thrombocytopenia (platelet count less than 50 x 109/L)
 within 72 hours of major surgery with risk of severe bleeding – defer and reassess
post-operatively
 previously documented hypersensitivity (e.g. priapism or ischaemic necrosis)
 acute clinically significant bleed – defer and reassess stroke versus bleeding risk
within three months
 decompensated liver disease or deranged baseline clotting screen (initial INR
greater than 1.5)
 pregnancy and within 48 hours postpartum. Warfarin is teratogenic and can cause
foetal bleeding. It is also associated with spontaneous abortion and peri-natal
bleeding (Australian Drug Evaluation Committee 2015)

Relative contraindications to warfarin therapy include:
 previous history of intracranial haemorrhage – seek specialist opinion
 recent major extracranial bleed within the last six months where the cause has not
been identified or treated – defer the decision for warfarin therapy
 peptic ulcer within last three months – defer until peptic ulcer treatment completed

Ensure peptic ulcer preventative therapy is initiated whilst on anticoagulant
 recent history of recurrent falls in patient at higher risk of bleeding (i.e. HAS-BLED
score greater than or equal to 3)
Guidelines for warfarin management in the community -5-
 dementia or marked cognitive impairment with poor medicines adherence and no
carer support
 chronic alcohol abuse, especially if binge drinking
 untreated or poorly controlled hypertension, consistently greater than 160/90
mm/Hg

Warfarin may be used during breast feeding. It has not been detected in breast milk at
doses up to 12 mg per day. Higher doses may require periodic INR monitoring of the
infant (National Institute of Health, USA 2015; Rossi 2015)

1.4 Initiation of warfarin
When initiating warfarin, it is important to involve the patient ensuring he or she
understands the benefits and potential side effects as well as the monitoring that is
necessary with warfarin therapy. Obtain patient consent and document in the clinical
notes

Consideration should be given to using 1 mg tablets only, particularly for patients who
have difficulty with reading or with numbers. This may assist in reducing confusion until
a stable dose is achieved

There are two methods for initiating warfarin, depending on the patient’s level of risk for
thrombotic events:
 low thrombotic risk patients (i.e. AF)
 high thrombotic risk patients (e.g. DVT)

Tables 5 and 6 recommend dose changes based on the assumption that the patient
has taken daily doses as recommended. Adherence to therapy should be checked prior
to adjusting doses in response to an INR result

Post-operative patients can be restarted with their ‘normal’ pre-operative maintenance
dose of warfarin without re-loading. See section 1.8 for information on stopping
warfarin for procedures

1.4.1 Patients at low risk of thrombosis (i.e. AF)
No heparin cover is required for patients at low risk of thrombosis and a low initial dose
regimen starting with 3 mg warfarin is recommended. The time taken to reach a
therapeutic INR is not critical; for 85 per cent of patients, this is achieved by day 29
(Clarke et al. 2006)

The regimen shown in Table 5 is based on weekly INR testing taken on day 1
(baseline), day 8 and day 15. Stabilisation of warfarin needs to take into account
factors that influence the INR or affect the risk of bleeding. Note that older people tend
to respond more slowly with changes to the INR. However, rarely, there may also be
patients who are more sensitive to the effects of warfarin. If there are clinical concerns
regarding response to warfarin, INR monitoring should be conducted more frequently
(e.g. every three to four days). In these instances dose adjustments should be based
on clinical judgement as the recommended protocol in Table 5 would no longer apply

Guidelines for warfarin management in the community -6-
Table 5 Regimen for Initiation of Warfarin in Patients at Low Risk of Thrombosis
(Target range of INR 2 – 3)
Day to take INR test INR Daily Warfarin Dose
(Initiation = day 1) (until next INR test)
Day 1 Obtain Baseline INR 3 mg (provided baseline INR is 1.4 or less)
Increase to 6 mg
Less than 1.4 Check INR again on Day 11 or 12
Refer to Section 1.13 for guidance on dosing
1.4 – 1.5 Increase to 5 mg
1.6 – 1.8 Increase to 4 mg
Day 8
1.9 – 2.1 Maintain 3 mg
2.2 – 2.5 Reduce to 2.5 mg
2.6 – 2.7 Reduce to 2 mg
2.8 – 3 Omit one to two daily doses,
then reduce to 1 mg
Stop Warfarin
#
Greater than 3 Check causes and indication
Repeat INR in three to five days
If warfarin definitely indicated, restart at 1 mg
Day 15 Check INR and adjust dose according to section 1.5 – Subsequent
and weekly thereafter Maintenance Dosing Using Warfarin
Source: Janes, Challis & Fisher 2004
#
If INR is abnormally high (i.e. greater than 5), refer to section 1.7 Management of High INR

1.4.2 Patients at high risk of thrombosis (e.g. DVT)
For patients at high risk of thrombotic events, heparin cover is required. Start warfarin
on the same day as therapeutic heparin or LMWH* and overlap for a minimum of five
days, until target INR has been reached for at least two consecutive days (Pisters et al

2010; Rossi 2015). For initiation, a starting dose of 5 mg warfarin with daily INR
monitoring for a minimum of five days is recommended

Guidelines for warfarin management in the community -7-
Table 6 Regimen for Initiation of Warfarin for High Risk Patients (Target range of
INR 2 – 3*)
Day to take INR test INR Daily Warfarin Dose
(Initiation = day 1) (until next INR test)
Day 1 Less than 1.4 5 mg
Less than 1.8 5 mg
Day 2 1.8 - 2 1 mg
#
Greater than 2 Nil
Less than 2 5 mg
2 - 2.5 4 mg
2.6 - 2.9 3 mg
Day 3
3 – 3.2 2 mg
3.3 – 3.5 1 mg
#
Greater than 3.5 Nil
Less than 1.4 10 mg
1.4 - 1.5 7 mg
1.6 – 1.7 6 mg
1.8 – 1.9 5 mg
Day 4
2 – 2.3 4 mg
2.4 – 3 3 mg
3.1 – 3.2 2 mg
3.3 - 3.5 1 mg
#
Greater than 3.5 Nil
Source: adapted from Kovaks et al. 2003; Gedge et al. 2000
* Exercise caution in patients with impaired renal function (calculated creatinine clearance is less than 30
mL/min) where LMWH can accumulate and contribute to bleeding

#
If INR is abnormally high (i.e. greater than 5), refer to section 1.7 Management of High INR

Note: Dose modification is required for patients with mechanical heart valves as the target INR range is
higher (2.5 – 3.5)

After Day 4 clinicians should continue regular INR monitoring every three to four days
until stabilised and if the patient is still on heparin or LMWH review the ongoing need
for these additional anticoagulants. Note that a change in the INR of 0.5 over three
days or 1 over seven days is considered unstable. Dose adjustments during this period
will need to be based on clinical judgement; if unsure seek advice. After INR results
have been stabilised, refer to subsequent maintenance dosing recommendations
(Section 1.5)

1.5 Subsequent maintenance dosing using warfarin
The following regimen (see Table 7) can be used for ongoing maintenance after
stabilisation. Clinicians should reflect on whether the patient has had INR variations in
the past to guide future adjustments in maintenance doses. Changes are
recommended based on confirmation that regular daily doses have been taken as
prescribed and the patient has had a consistent diet. Clinicians should consider
Guidelines for warfarin management in the community -8-
available tablet strengths and the patient’s ability to break scored tablets when
prescribing future doses

The dose modifications in Table 7 below are based on the total weekly dose of
warfarin. The weekly dose can be prescribed using a range of dosing regimens (e.g

alternate day dosing or dose regimens with different doses for weekdays compared to
the weekend). Dose modifications based on the total weekly dose also enable dose
adjustments for low dose regimens whereas a change would not be recommended if
calculations were based on the daily dose

Table 7 Regimen for Subsequent Maintenance Dosing Using Warfarin (Target
range of INR 2 – 3*)
INR Dosage adjustment
Less than 1.5 Increase weekly dose by 20%
1.5 – 1.9 No change – recheck in one week
If persistent, increase weekly dose by 10%
2–3 No change
3.1 – 3.9 No change – recheck in one week
If persistent, decrease weekly dose by 10%–20%
Omit one dose
4 – 4.9 Decrease weekly dose by 10%–20%
Re-check INR in two to five days
Greater than or equal to 5 See section 1.7 – Management of High INR
Source: adapted from Guidelines & Protocols Advisory Committee 2010
* Note: Dose modification is required for patients with mechanical heart valves as the target INR range is
higher (2.5 – 3.5)

Worked examples of dose modifications:
1. Current dose regimen of 1 mg daily (equates to 7 mg weekly). If INR result is 1.6:
Recommended dose adjustment is an increase of 7 mg x 10% = 0.7 mg

Example of new dose regimen:
Mon Tue Wed Thur Fri Sat Sun Total
weekly
dose
Current 1mg 1mg 1mg 1mg 1mg 1mg 1mg 7mg
dose
Suggested 1mg 1mg 1mg 1mg 1mg 1mg 2mg 8mg
new dose
(1)
Suggested 1mg 1mg 1.5mg 1mg 1mg 1.5mg 1mg 8mg
new dose
(2)
2. Current dose regimen of 4 mg on Monday, Wednesday and Friday, 3 mg every
other day (equates to 24 mg weekly). If INR result is 4.2:
Recommended dose adjustment is a dose omission then a reduction of 24 mg x 10%-
20% = 2.4-4.8 mg over the week

Example of new dose regimen: omit one dose; then change dose to 3 mg daily

Guidelines for warfarin management in the community -9-

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Frequently Asked Questions

What are guidelines for taking warfarin?

Warfarin

1. About warfarin Warfarin is a type of medicine known as an anticoagulant, or blood thinner. It makes your blood flow through your veins more easily. ...
2. Key facts It's usual to take warfarin once a day, normally in the evening. ...
3. Who can and can't take warfarin Warfarin can be taken by adults and children. ...

More items...

What is a typical recommended dose of warfarin?

Warfarin should usually be started at a dose of 5 mg per day.A 10-mg dose more frequently results in a supratherapeutic international normalized ratio (INR). Amiodarone, fluconazole, metronidazole, trimethoprim- sulfamethoxazole, and many other drugs inhibit the metabolism of warfarin.

How to adjust warfarin?

consider resumption of prior maintenance dose if factor causing decreased INR is transient [eg: missed warfarin dose (s)] if adosage adjustment is needed, increase maintenance dose by 10%–20% consider a booster dose of 1 ½ – 2 times daily maintenance dose

Is warfarin an anticoagulant?

Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent stroke in people who have atrial fibrillation, valvular heart disease or artificial heart valves.