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INR Testing

Key Messages INR PDF
Initiation of warfarin therapy
Monitoring INR
Other issues for INR management

Other issues for INR management

Ceasing warfarin therapy

Warfarin therapy can be discontinued abruptly when the duration of treatment is completed. Prospective studies have not indicated a rebound prothrombotic state and there is no need for gradual withdrawal.

Dental extractions and preoperative warfarin doses

For minor surgical procedures, the warfarin dose should be stopped or adjusted to achieve a target INR of approximately 2.0 on the day of surgery. For major surgery, warfarin should be stopped at least three days prior to surgery; further actions will depend on resulting INR levels and the thrombotic risk of the condition for which the patient is receiving anticoagulation.

Anticoagulation does not need to be stopped for dental extraction for patients with an INR less than 3.0.

Warfarin should be avoided in pregnancy

Pregnant women should never take warfarin, as it is teratogenic (Medsafe, 2002). Women of child-bearing age on warfarin should be using effective contraception and contact their doctor urgently (by six weeks) if they think they are pregnant.

Standardised procedures for rest homes

The establishment of a systematic approach to the use of warfarin is particularly important in rest homes. There are often several health professionals involved in the prescribing, dose adjustment and administration of warfarin. It is essential that there are robust systems in place to guide the processes.

Clear written instructions are necessary to guide rest home staff. Verbal instructions on warfarin therapy in rest homes, for example on changing doses, are fraught with risk and should be avoided whenever possible.

Near patient testing

Near patient testing of INR levels is effective for selected patients. There are risks if patients are not well motivated, or do not fully understand the process, or if quality assurance procedures are not of a high standard.

If you would like to check your current system for maintenance of INR levels you could use bpac’s audit, ‘Practice audit of the systematic management of INR levels’, which has been sent to every practice and is available from

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