Empiric warfarin dose adjustment with prednisone therapy. A randomized, controlled trial

Area of Science:

• Pharmacology
• Clinical Pharmacy
• Internal Medicine

Background:

• Warfarin therapy requires careful monitoring of the international normalized ratio (INR).
• Interactions between warfarin and medications like prednisone can lead to non-therapeutic INR levels.
• Current practice often involves reactive dose adjustments after initiating interacting medications.

Purpose of the Study:

• To evaluate the effectiveness of preemptive warfarin dose reduction in preventing non-therapeutic INR during prednisone co-administration.
• To compare preemptive dose adjustment with reactive dose adjustment in patients on warfarin and initiating prednisone.

Main Methods:

• A randomized controlled trial comparing preemptive warfarin dose reduction (10-20%) versus reactive dose adjustment.
• Patients were randomized into intervention (preemptive reduction) and control (reactive adjustment) groups.
• INR was monitored within 7 days of initiating prednisone, with outcomes including supratherapeutic INR, INR control, and adverse events.

Main Results:

• The intervention group showed a non-significant reduction in supratherapeutic INR compared to the control group (10.0% vs. 29.4%).
• A significantly higher percentage of patients in the intervention group experienced subtherapeutic INR compared to the control group (40% vs. 5.9%, P=0.02).
• No significant differences were observed in warfarin-associated bleeding or thromboembolic events between groups.

Conclusions:

• Preemptive warfarin dose reduction during prednisone initiation did not effectively prevent supratherapeutic INR.
• Preemptive dose reduction increased the likelihood of subtherapeutic INR compared to reactive adjustment.
• Reactive INR monitoring and warfarin dose adjustment remain the recommended approach for managing prednisone-warfarin co-administration.