Warfarin maintenance: management of high and low INRs
Use the following guides to adjust maintenance doses for patients already stabilised on warfarin to achieve a target INR (international normalised ratio) of 2.5 ± 0.5.
- Consider recent INR trends - avoid adjusting warfarin doses based on an asymptomatic, single, unexplained out-of-range INR, unless clinically significant
- Use the MedicineWise Anticoagulant Safety Checklist to identify causes for INR instability and guide maintenance dose adjustments
- Dose adjustments should be based on the total weekly dose of warfarin
- When changing the warfarin dose, check INR every 7–14 days until the INR is stable
- Consider available tablet strengths and the patient’s ability to break scored tablets when prescribing future doses.
- Older people may take longer to respond to dose changes
- Missed doses will be reflected in the INR in 2–5 days
- For warfarin dose initiation, refer to MedicineWise News
Dose adjustments should be based on the total weekly dose of warfarin.
||≤ 1.5||1.6– 1.9||2–3
||Increase weekly dose by 15%[B]||
Continue current dose
If repeat INR falling or low for 2 consecutive INRs, increase weekly dose by 10%
|Continue current dose
||Continue current dose
If repeat INR rising or high for 2 consecutive INRs, reduce weekly dose by 10%
|Omit warfarin dose for 1 day, reduce weekly dose by 10%
||See Table 2 for patients on warfarin with high INR and no bleeding and Table 3 for patients on warfarin with bleeding
|Next INR test
||7–14 days[C]||7–14 days[C]||Continue current INR testing interval
||7–14 days[C]||7–14 days[C]|
[A] Clinical judgment may allow variation in the application of the algorithm.
- to avoid missing an INR that has been rising since the last INR level, particularly when the INR ≥ 4
- if a cause for a change in INR cannot be identified
- if there has been a dramatic change from the previous INR, e.g. from 3.0 to 1.6.
The advice in Tables 2 and 3 is taken from an ‘Update of Consensus Guidelines for Warfarin Reversal’ on behalf of the Australasian Society of Thrombosis and Haemostasis.
If the patient is bleeding consider urgent hospital referral is recommended. Prothrombinex-VF and fresh frozen plasma provide immediate reversal. Vitamin K1 is essential for sustaining the reversal achieved.
Table 2: Management of patients on warfarin with high INR and no bleeding
|INR 4.5–10.0 and no bleeding
|INR >10.0 and no bleeding
[D] Recent major bleed (within previous 4 weeks) or major surgery (within previous 2 weeks), thrombocytopenia (platelet count < 50 x 109/L), known liver disease or concurrent antiplatelet therapy.
[E] Extrapolated from oral vitamin K data in absence of IV data.
|INR ≥1.5 with life-threatening[G] (critical organ) bleeding
Stop warfarin therapy and administer:
|INR ≥ 2.0 with clinically significant bleeding (not life threatening)
Stop warfarin therapy and administer:
|Any INR with minor bleeding
Repeat INR the following day and adjust warfarin dose to maintain INR in the target therapeutic range
If bleeding risk is high[I] or INR > 4.5, consider vitamin K1 1–2 mg orally or 0.5–1 mg IV
[F] Indication for warfarin therapy should be reviewed; if clinically appropriate, consider permanent cessation.
[G] Includes intracranial bleeding.
[H] Consider administering a Prothrombinex-VF dose less than 50 IU/kg when INR 1.5–1.9.
[I] Recent major bleed (in the previous 4 weeks) or major surgery (in the previous 2 weeks), thrombocytopenia (platelet count < 50 x 109/L), known liver disease or on current antiplatelet therapy.
- Kim YK, Nieuwlaat R, Connolly SJ, et al. Effect of a simple two-step warfarin dosing algorithm on anticoagulant control as measured by time in therapeutic range: a pilot study. J Thromb Haemost 2010;8:101–6.
- Tran HA, Chunilal SD, Harper PL, et al. An update of consensus guidelines for warfarin reversal. Med J Aust 2013;198:doi:10.5694/mja12.10614. https://www.mja.com.au/journal/2013/198/4/update-consensus-guidelines-warfarin-reversal (accessed 25 June 2013).