This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
[{'content': 'Which of the following is a Class Ib drug? \nSelect and explain. \nA. Encainide, B. Flecainide, C. Lidocaine, D. Moricizine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Class 1 Drugs with local anesthetic action block sodium channels and reduce the sodium current, INa. They are the oldest group of antiarrhythmic drugs and are still widely used.Drugs belonging to Subgroup 1B1) Lidocaine2) MexiletineReference: Katzung Pharmacology; 13th edition; Chapter 14; Agents Used in Cardiac Arrhythmias', 'role': 'assistant'}]