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: Pharmacology
[{'content': 'Polymorphic ventricular tachycardia can occur when terfenadine(antihistaminic): \nSelect and explain. \nA. Is coadministrator with azithromycin, B. Is coadministrator with fluconazole, C. Is given in higher doses, D. Reduces QT interval', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Torsades de pointes (polymorphic ventricular tachycardia) occurs\xa0when terfenadine is taken in higher doses or when hepatic\xa0metabolism is impaired by disease or by drugs which inhibit the\xa0cytochrome P450 responsible for metabolism of terfenadine.\xa0Drugs include erythromycin, clarithromycin, ketoconazole and\xa0itraconazole. Azithromycin and fluconazole that are excreted\xa0unchanged in the urine have not been associated with impaired\xa0metabolism of terfenadine. Terfenadine blocks the delayed rectifier\xa0potassium channels and prolongs cardiac repolarization and the\xa0QT interval.', 'role': 'assistant'}]