Warfarin review

Posted in Anticoagulation.

Why this page is important: If a patient's warfarin time in range (TIR) is less than 65% then the patient needs to be asessed for warfarin suitabiliy. Here is my checklist of assessing both long term low TIR & for adjusting doses for acute out of ranges.

Warfarin INR out of range long term

Review all patients with Time in Range (TIR) <65%

Are they taking any medication which may interact with warfarin
Are they being compliant
Have they recently started or stopped smoking
- Smoking enhances warfarin
Have they had any weight loss or gain
Have they had any acute illness (such as gastroenteritis)
Have they suffered from longer bouts of diarrhoea and vomiting
Do they drink more alcohol than the recommended 1-2 drinks per day or any episodes of binge drinking
Do they take recreational drugs
Are they taking any herbal remedies which interact with warfarin
Are they eating any interacting food or drink

If none of the above can be rectified or adjusted to improve time in range the consider a switch to a DOAC

see review whether to switch from warfarin to DOAC

See how to switch from warfarin to DOAC

Warfarin INR out of range acutely

INR	Recommendation
>8.0 with no bleeding or minor bleeding	stop warfarin and give 0.5–1 mg phytomenadione by slow intravenous injection, or 5 mg by mouth The dose of phytomenadione may be repeated after 24 hours, if the INR is still too high Restart warfarin when the INR is less than 5.0
6.0–8.0 with no bleeding or minor bleeding	stop warfarin Restart warfarin when the INR is less than 5.0
<6.0, but more than 0.5 units above the target value	Reduce dose or stop warfarin Restart warfarin when the INR less than 5.0
high, but < 5.0	The warfarin dose will need to be reduced and/or one or two doses may need to be omitted the INR should then be measured 2 or 3 days later to ensure that it is falling
lower than the target	Depending on the INR, the warfarin dose may need to be (temporarily) increased, and sometimes a booster dose may be required the INR should then be measured 2 or 3 days later to ensure that it is increasing

In general, when adjusting the dose, a 15% change in dose is expected to result in a change in the INR of 1, and a 10% dose adjustment is expected to result in a 0.7–0.8 change in the INR

References

NICE Guidelines

https://www.pharmaceutical-journal.com/cpd-and-learning/learning-article/can-i-take-herbal-products-or-dietary-supplements-with-my-warfarin/10883412.article?firstPass=false

Warfarin phytomenadione

Warfarin review

Warfarin INR out of range long term

Review all patients with Time in Range (TIR) <65%

If none of the above can be rectified or adjusted to improve time in range the consider a switch to a DOAC

Warfarin INR out of range acutely

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Warfarin review

Warfarin INR out of range long term

Review all patients with Time in Range (TIR) <65%

If none of the above can be rectified or adjusted to improve time in range the consider a switch to a DOAC

Warfarin INR out of range acutely

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