Elevated Prothrombin Time/International Normalized Ratio after Concomitant Administration of Erlotinib in Patients Receiving Warfarin: A Report on Two Cases

Hiroyuki Watanabe, Yu Nishibatake, Kojiro Hata, Yoko Makihara, Yoichi Nakanishi and Satohiro Masuda

Department of Pharmacy, Kyushu University Hospital, Japan
Research Institute for Diseases of the Chest, Kyushu University, Japan

^*Correspondance to: Hiroyuki Watanabe 

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Abstract:

Adverse interactions between warfarin and cytotoxic agents are well documented; however, interactions between warfarin and erlotinib are not well characterized. Here we report two patients with non-small cell lung cancer in whom concomitant treatment with erlotinib and warfarin resulted in elevated prothrombin time-international normalized ratio (PT-INR) values. In the first case, the PT-INR value increased from 2.24 to 2.73 9 days after initiating erlotinib treatment in a 59-yearold Japanese man receiving prophylactic warfarin therapy for cardiovascular disease. However, erlotinib did not adversely affect the hepatic function in this patient. In the second case, the PTINR value increased from 1.58 to 7.54 7 days after initiating erlotinib treatment in a 61-year-old Japanese man receiving prophylactic warfarin therapy for cerebral infarction; this was accompanied by bleeding diathesis (purpura). In both cases, PT-INR was well maintained by warfarin therapy prior to initiating erlotinib treatment. Our experience with these cases underlines the importance of the careful monitoring of the PT-INR value and appropriate adjustment of warfarin dosage in patients receiving concomitant erlotinib and warfarin therapy.

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Cite the Article:

Watanabe H, Nishibatake Y, Hata K, Makihara Y, Nakanishi Y, Masuda S. Elevated Prothrombin Time/ International Normalized Ratio after Concomitant Administration of Erlotinib in Patients Receiving Warfarin: A Report on Two Cases. Ann Clin Case Rep. 2016; 1: 1210.