Prescribing Safety Assessment (PSA) Practice Exam

What is a significant interaction of erythromycin with warfarin?

1. Erythromycin decreases INR levels

2. Erythromycin has no effect on INR levels

3. Erythromycin increases INR levels in patients on Warfarin

4. Erythromycin enhances warfarin absorption

The correct answer is: Erythromycin increases INR levels in patients on Warfarin

Erythromycin is a macrolide antibiotic that can interact with warfarin, an anticoagulant medication. The correct choice identifies that erythromycin increases the International Normalized Ratio (INR) levels in patients who are on warfarin. The reason for this interaction lies in the fact that erythromycin inhibits certain cytochrome P450 enzymes, specifically CYP3A4, which are involved in the metabolism of warfarin. When erythromycin is administered alongside warfarin, it can decrease the metabolism of warfarin, leading to higher concentrations of warfarin in the bloodstream. As a consequence, this enhances the anticoagulant effect of warfarin, resulting in increased INR levels. Elevated INR indicates a higher risk of bleeding, making it crucial for healthcare providers to monitor patients closely and adjust the warfarin dosage when erythromycin is prescribed. Understanding this interaction is vital for safe prescribing practices, as it highlights the importance of considering drug-drug interactions when managing patients who require anticoagulation therapy.