What is the next step for a patient on warfarin (Coumadin) with a subtherapeutic International Normalized Ratio (INR) of 1.9 after being held since an INR of 4.1 on 6-5-2025?

From the Guidelines

The patient should restart warfarin therapy at their previous maintenance dose immediately, without a loading dose, to minimize the risk of thrombotic events due to the current subtherapeutic INR of 1.9. Since the INR has fallen after being held for about two weeks (from June 5,2025), the patient is now at increased risk for thrombotic events 1. Resume the warfarin immediately, but do not administer a loading dose as this could lead to excessive anticoagulation, as suggested by the American Heart Association/American College of Cardiology Foundation guide to warfarin therapy 1.

Key Considerations

• Schedule an INR check within 5-7 days to ensure the patient is trending toward their target range (typically 2.0-3.0 for most indications) 1.
• If the INR remains subtherapeutic at the follow-up check, a modest dose increase of 5-10% may be warranted, considering the patient's response to warfarin and the risk of bleeding or thrombosis 1.
• During this transition period, consider whether bridging anticoagulation with low molecular weight heparin is necessary based on the patient's thrombotic risk, as the goal is to safely return the patient to a therapeutic INR while balancing the risks of thrombosis and bleeding 1.

Monitoring and Dose Adjustments

• The INR is usually checked daily until the therapeutic range has been reached and sustained for 2 consecutive days, then 2 or 3 times weekly for 1 to 2 weeks, then less often, according to the stability of the results 1.
• When dose adjustments are required, frequent monitoring is resumed to ensure the patient's INR remains within the therapeutic range, minimizing the risk of adverse events 1.

From the FDA Drug Label

The individual dose and interval should be gauged by the patient’s prothrombin response Maintenance Most patients are satisfactorily maintained at a dose of 2 to 10 mg daily. If the patient forgets to take the prescribed dose of warfarin sodium tablets at the scheduled time, the dose should be taken as soon as possible on the same day The PT should be determined daily after the administration of the initial dose until PT/INR results stabilize in the therapeutic range.

The patient's warfarin was held since 6-5-2025 due to an INR of 4.1, and now the INR is 1.9.

• The INR of 1.9 is subtherapeutic, indicating that the patient is not adequately anticoagulated.
• To resume anticoagulation, the patient's warfarin dose should be restarted, and the dose should be adjusted based on the patient's prothrombin response.
• The patient should be monitored closely with regular PT/INR determinations to ensure that the INR returns to the therapeutic range.
• The dose and interval of warfarin should be gauged by the patient's prothrombin response to maintain the INR within the therapeutic range 2.

From the Research

Patient's Current Status

• The patient's warfarin medication was on hold since 6-5-2025 due to an INR of 4.1.
• The patient's current INR is 1.9, which is subtherapeutic.

Next Steps

• According to the study 3, restarting warfarin at the previous maintenance dose may take a median of 20.5 days to achieve a therapeutic INR.
• However, administering a loading dose of approximately 40% more than the previous daily maintenance dose for 2 or 3 days may shorten the time to achieve a therapeutic INR to a median of 5.0 days or 6.0 days, respectively.
• The study 4 suggests that a simple low-dose regimen for starting warfarin therapy can be safe and accurate, with a mean time to achieve a therapeutic INR of 6.7 +/- 3.3 days.
• It is essential to consider the patient's individual characteristics, such as kidney function, to determine the appropriate warfarin dose, as patients with chronic kidney disease or end-stage renal disease may require lower warfarin doses 5.

Considerations

• The patient's INR has decreased significantly since the medication was on hold, indicating a need to reinitiate warfarin therapy.
• The risk of thromboembolic events and bleeding complications should be carefully considered when determining the next steps for the patient's warfarin therapy.
• Alternative anticoagulation options, such as low-molecular-weight heparin (LMWH), may be considered in certain situations, as they have been shown to be effective and safe in the treatment of deep vein thrombosis and venous thromboembolism 6.