A 55-year-old man with a 20-year history of chronic hepatitis C and compensated cirrhosis (Child-Pugh class A) develops a 4.2 cm hepatocellular carcinoma on surveillance imaging and is started on sorafenib 400 mg twice daily. He has a concurrent history of atrial fibrillation and takes warfarin 5 mg daily for anticoagulation, with his INR previously stable at 2.5 for the past six months. One week after initiating sorafenib, he presents to the emergency department with gross hematuria and flank discomfort. His blood pressure is 138/86 mmHg, heart rate is 78 bpm, and temperature is 37.1°C. Repeat laboratory studies reveal an INR of 8.2, with no changes in diet, alcohol use, or other medications. Which of the following best explains this interaction?

1. A)Sorafenib induces hepatic microsomal enzymes, increasing warfarin effect
2. B)Warfarin hepatotoxicity is enhanced by concurrent sorafenib use
3. C)Sorafenib inhibits warfarin metabolism via CYP2C9 inhibitionGABARITO
4. D)Sorafenib competitively displaces warfarin from protein binding
5. E)Sorafenib causes thrombocytopenia, preventing platelet aggregation and potentiating bleeding