A Case of Elevated Prothrombin Time-International Normalized Ratio (PT-INR) Associated with Concurrent Use of Erlotinib and Warfarin / 대한내과학회지

ABSTRACT

Erlotinib, an orally active epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), is indicated for EGFR mutation-positive patients with poor performance status. Erlotinib is also used as a second-line agent in patients who show disease progression after failure of first-line therapy. Warfarin is administered in patients with advanced cancer for the prevention or treatment of venous thromboembolism. Both erlotinib and warfarin are metabolized in the human liver primarily by the CYP3A4 enzyme system. Thus, erlotinib may inhibit the metabolism of warfarin and clinicians should pay attention to the possible interaction between the two drugs when they are administered concurrently. We report the case of a 50-year-old man who showed changes in the prothrombin time-international normalized ratio (PT-INR) after coadministration of erlotinib and warfarin.