HNELHD CG 12 04 Warfarin Age Adjusted Dosing in Adults

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Warfarin Age Adjusted Dosing in Adults HNELHD CG 12_04

Clinical Guideline

Warfarin Age Adjusted Dosing in AdultsDocument Registration Number: HNELHD CG 12_04

Sites where Guideline applies All HNE Health Facilities

This Guideline applies to:

1. Adults Yes

2. Children up to 16 years No

3. Neonates less than 29 days No

Target audience Registered Medical Officers

Description Procedure for initial dosing of warfarin according to patientsage and dose adjustment according to INR

Keywords warfarin, INR, anticoagulantReplaces Existing Guideline? Yes

Registration Numbers of SupersededDocuments

Warfarin Age-adjusted Dosing GNAH_0144 from March2009

Related documents (Policies, Australian Standards, Codes of Conduct, legislation etc)

NSW Health Safety Notice SN:006/07 Warfarin (revised) (12 April 2007)

http://internal.health.nsw.gov.au/quality/sabs/pdf/sn20070412.pdf

HNE QUMC Communiqu Independent Check

http://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/81453/Independent_Check_communique_Jan_2011.pdf

HNE Policy Compliance Procedure PD2009_077:PCP9 Medicines requiring a double check whenadministered to Adults

http://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/76746/PD2009_077_PCP_9_V4_Double_Checking_of_Medications.pdf

HNE QUMC Communiqu High Risk Medicines

http://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0005/85406/HNE_AQUM_High_Risk_Medicines_communique.pdf

National Inpatient Medication Chart User Guide (including paediatric versions) January 2011http://www.safetyandquality.gov.au/internet/safety/publishing.nsf/Content/4DA7912710DA1FBBCA25778A00151C1E/$File/NIMC%20User%20Guide.pdf

Position responsible for GuidelineGovernance

Professor Ian Whyte, Chair, HNE Quality Use of MedicinesCommittee

Guideline Contact Officer Professor Ian Whyte, Chair, HNE Quality Use of MedicinesCommittee

Contact Details [email protected]

4921 1283

Date authorised 13 December 2011

Author is ing body HNE Quality Use of Medicines Committee

This Guideline contains advice ontherapeutics

Yes

Issue Date 19 January 2012

Date for review 1 December 2014

TRIM number 12/28-3-4

Version One January 2012
http://internal.health.nsw.gov.au/quality/sabs/pdf/sn20070412.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/81453/Independent_Check_communique_Jan_2011.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/81453/Independent_Check_communique_Jan_2011.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/76746/PD2009_077_PCP_9_V4_Double_Checking_of_Medications.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/76746/PD2009_077_PCP_9_V4_Double_Checking_of_Medications.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0005/85406/HNE_AQUM_High_Risk_Medicines_communique.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0005/85406/HNE_AQUM_High_Risk_Medicines_communique.pdfhttp://www.safetyandquality.gov.au/internet/safety/publishing.nsf/Content/4DA7912710DA1FBBCA25778A00151C1E/$File/NIMC%20User%20Guide.pdfhttp://www.safetyandquality.gov.au/internet/safety/publishing.nsf/Content/4DA7912710DA1FBBCA25778A00151C1E/$File/NIMC%20User%20Guide.pdfmailto:[email protected]:[email protected]://www.safetyandquality.gov.au/internet/safety/publishing.nsf/Content/4DA7912710DA1FBBCA25778A00151C1E/$File/NIMC%20User%20Guide.pdfhttp://www.safetyandquality.gov.au/internet/safety/publishing.nsf/Content/4DA7912710DA1FBBCA25778A00151C1E/$File/NIMC%20User%20Guide.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0005/85406/HNE_AQUM_High_Risk_Medicines_communique.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0005/85406/HNE_AQUM_High_Risk_Medicines_communique.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/76746/PD2009_077_PCP_9_V4_Double_Checking_of_Medications.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/76746/PD2009_077_PCP_9_V4_Double_Checking_of_Medications.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/81453/Independent_Check_communique_Jan_2011.pdfhttp://intranet.hne.health.nsw.gov.au/__data/assets/pdf_file/0003/81453/Independent_Check_communique_Jan_2011.pdfhttp://internal.health.nsw.gov.au/quality/sabs/pdf/sn20070412.pdf


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Version One January 2012 Page 2

Prerequisites: Initiation of warfarin and subsequent dosing adjustments according toINR must be undertaken by a medical officer

Summary: This Guideline sets out the steps to be followed when commencing andadjusting the dose of warfarin. The procedural components of thedocument such as, Preparation of patient, Preparation of equipment,Technique, Cleaning up and Documentation are considered

mandatory.Guideline Note : This document reflects what is currently regarded as safe and

appropriate practice. However in any clinical situation there may bemany factors that cannot be covered by a single document andtherefore does not replace the need for the application of clinicaljudgment in respect to each individual patient.

OUTCOMES

1 Safe and appropriate initiation and dose adjustment of warfarin

2 Provide guidelines for age appropriate commencement doses of warfarin and adjustment

according to INR.

GLOSSARY

List of abbreviations, acronyms and terms with their definitions

Acronym or Term Defini tion

Baseline INR INR taken on day 1 prior to commencement of warfarin sodium

INR International Normalised Ratio

IV Intravenously

mg milligramNIMC National Inpatient Medication Chart

PO orally

Vitamin K phytomenadione

BACKGROUND

In 1999, investigators from Adelaide published a comparison between a warfarin loading protocoladjusting doses for age with an existing protocol (Fennerty's protocol) and empirical dosing1.

Patients using the age-adjusted protocol achieved a stable, therapeutic International NormalisedRatio (INR) more rapidly than either of the other groups. The age-adjusted group also had a lowerproportion of patients experiencing an INR > or = 4 in the first week as well as a lower proportionhaving doses withheld in the first week.

A modified version, taking into account further risk factors was published in 2003. When trialled,this protocol resulted in most patients rapidly achieving a stable INR with minimal overanticoagulation (63% of patients attained a stable INR after 4 days and 86% after a further twodays treatment)2.

The protocol coped with other variables shown to affect maintenance warfarin dosing such asweight, gender, pharmacological factors affecting clearance and the presence of designated riskfactors3.

The early recognition of warfarin sensitivity (via daily INRs for 5 days) is considered to be theabsolute key to warfarin initiation and more important than the choice of dose.


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GUIDELINE

Drug and Presentation:

warfarin sodium 1 mg, 2 mg and 5 mg (Coumadin

) tablets

warfarin sodium 1 mg, 3 mg and 5 mg (Marevan

) tablets.

Notes: The two (2) available brands of warfarin sodium are not considered bioequivalent and

therefore cannot be substituted.

Coumadin

brand is routinely stocked by HNE facilities.

Ongoing Monitoring:

INR should be measured daily in the morning so that drug administration can occur at 4pm.

Warfarin sodium doses on days 2 4 are based on an INR measured 16 18 hoursafter the previous days dose.

Dose: According to age as shown in the table below:

warfarin dose warfarin dose warfarin dose warfarin dose

Day INR Age up to 50 yrs Age 51-65 yrs Age 66-80 yrs Age >80yrs

1


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PROCEDURES

Patient Preparation

Patients should be screened for co-existing diseases or conditions such as hepatic impairment,hypo/hyperthyroidism, congestive heart failure, renal impairment, hypoalbuminaemia and highvitamin K intake plus recent trauma, surgery or bleeding problems.

Baseline INR: The day 1 INR reflects pre-warfarin baseline.

If baseline INR 1.4, reasons for coagulopathy should be assessed2

.

Patients with low albumin may be particularly sensitive to the anticoagulant effects of warfarin.

Staff Preparation

It is mandatory for staff to follow relevant: Five moments of hand hygiene, infection control,moving safely or safe manual handling, and documentation practices.

Medical staff should be familiar with the use of warfarin sodium and its indications and precautions.

Clinical staff must use the specific section for ordering warfarin sodium on the National InpatientMedication Chart (NIMC).

Patient counselling including the provision of written information should occur and be documentedin the Warfarin Education Record section of the NIMC.

Prescribing and Administration

To facilitate dosing decisions the INR target range and INR results are to be recorded on theNIMC.

The required dose should be prescribed following review of morning INR results. This is bestcompleted by medical staff familiar with the patients medication management.

Administer required dose at 4 pm.

For patients w ith active thrombosis continued co-administration of heparin or LMWH shouldoccur until:

- warfarin sodium has been administered for a minimum of 4 days, and- the INR reaches a therapeutic level for 2 consecutive days.

Addi tional notes:

Warfarin sodium is an anticoagulant and considered a high risk medicine.

The two (2) available brands of warfarin sodium are not considered bioequivalent. DO NOTsubstitute one brand for the other. Referto the following NSW Health Safety Notice for additional advice or information:

- NSW Health Safety Notice SN:006/07 Warfarin (revised) (12 April 2007)http://internal.health.nsw.gov.au/quality/sabs/pdf/sn20070412.pdf
http://internal.health.nsw.gov.au/quality/sabs/pdf/sn20070412.pdfhttp://internal.health.nsw.gov.au/quality/sabs/pdf/sn20070412.pdf


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IMPLEMENTATION PLAN

CG to be communicated across HNE Health via clinical networks, Area QUM Committee and othercommunication sources e.g. The Latest, Quality Matters and HNE Health website.

EVALUATION PLAN

IIMS monitoring of adverse outcomes

CONSULATION WITH KEY STAKEHOLDERS

Haematology Department HAPS/CMH

Area Quality Use of Medicines Committee endorsed 2011

REFERENCES

1. Roberts GW, Druskeit T, Jorgensen LE, Wing LM, Gallus AS, Miller C, Cosh D, Eaton VS. Comparisonof an age adjusted warfarin loading protocol with empirical dosing and Fennerty's protocol.Aust N Z JMed. 1999 Oct;29(5):731-6

2. Roberts GW, Helboe T, Nielsen CB, Gallus AS, Jensen I, Cosh DG, Eaton VS. Assessment of an age-adjusted warfarin initiation protocol.Ann Pharmacother. 2003 Jun;37(6):799-803

3. Baker RI, Coughlin PB, Gallus AS, Harper PL, Salem HH, Wood EM, et al. Warfarin reversal: consensusguidelines, on behalf of the Australasian Society of Thrombosis and Haemostasis. Medical Journal ofAustralia 2004;181(9):492-7