What is the next step for a patient with an INR of 1.6 on Clexane (enoxaparin) 40mg, with a target INR range of 2.5 to 3?

Management of Subtherapeutic INR in a Patient on Enoxaparin

For a patient with an INR of 1.6 (target range 2.5-3.0) who is currently on enoxaparin 40mg, the next step should be to continue enoxaparin while increasing the warfarin dose to achieve therapeutic anticoagulation.

Assessment of Current Situation

• Current INR: 1.6
• Target INR range: 2.5-3.0
• Current therapy: Enoxaparin 40mg (prophylactic dose)
• Status: Subtherapeutic anticoagulation

Management Algorithm

1. Continue Bridging Therapy

• Maintain enoxaparin 40mg while adjusting warfarin dose
• The American College of Chest Physicians (ACCP) guidelines recommend continuing bridging therapy with LMWH until the INR reaches the therapeutic range 1
• This approach ensures continuous anticoagulation protection while warfarin is being titrated

2. Adjust Warfarin Dosing

• Increase warfarin dose to achieve target INR of 2.5-3.0
• Use a validated dosing nomogram for warfarin adjustment 1
• Recheck INR within 1-2 weeks to assess response 1

3. Monitor for Efficacy and Safety

• Continue enoxaparin until INR is consistently in the therapeutic range (2.5-3.0) for at least two consecutive readings
• Once therapeutic INR is achieved, discontinue enoxaparin

Evidence-Based Rationale

The ACCP guidelines strongly recommend a therapeutic INR range of 2.0-3.0 (target 2.5) for patients on warfarin therapy 1. For this patient with a target range of 2.5-3.0, the current INR of 1.6 is significantly subtherapeutic.

Research has shown that patients with stable INRs who experience a single subtherapeutic INR have a low risk of thromboembolism in the ensuing 90 days 2. However, this patient's INR is significantly below the target range, warranting intervention.

The ACCP guidelines suggest against routinely administering bridging with heparin for patients with stable therapeutic INRs presenting with a single subtherapeutic INR value 1. However, this patient's INR is significantly below the target range and they are already on enoxaparin, indicating a higher risk situation requiring continued bridging.

Special Considerations

• Higher target INR range: The target range of 2.5-3.0 suggests this patient may have a mechanical heart valve or other condition requiring higher anticoagulation intensity 1
• Bleeding risk: Assess for any signs of bleeding before increasing warfarin dose
• Drug interactions: Review medications for potential interactions with warfarin that might be contributing to the subtherapeutic INR

Pitfalls to Avoid

1. Premature discontinuation of enoxaparin: Do not discontinue enoxaparin until the INR is consistently therapeutic
2. Excessive warfarin dosing: Avoid large loading doses which can lead to INR overshooting and increased bleeding risk
3. Inadequate follow-up: Ensure close monitoring of INR until stable in therapeutic range
4. Ignoring contributing factors: Investigate potential causes of the subtherapeutic INR (medication changes, dietary changes, missed doses)

By following this approach, the patient will maintain adequate anticoagulation through enoxaparin while the warfarin dose is optimized to achieve the target INR range.