This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'Apixaban is: \nSelect and explain. \nA. Antithrombin inhibitor, B. Direct Xa inhibitor, C. Platelet activator, D. Clotting Factor XII', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ref. KDT. Page. 617\nApixaban is an oral, direct, and highly selective factor Xa (FXa) inhibitor (of both free and prothrombinase-bound FXa independently of antithrombin III) for the prevention and treatment of thromboembolic diseases\n\nApixaban prolongs clotting tests such as prothrombin time (PT), INR, and activated partial thromboplastin time (aptt)\nApixaban is absorbed in the stomach and small intestine\n87% plasma protein bound.\nApixaban mainly undergoes o-demethylation and hydroxylation to metabolites\nGrapefruit juice may increase apixaban serum concentration.\nSt. John's wort will likely decrease apixaban serum concentration", 'role': 'assistant'}]