This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anaesthesia
[{'content': 'Local anaesthetic with maximum ionized form at physiological pH \nSelect and explain. \nA. Lignocaine, B. Etidocaine, C. Bupivacaine, D. Chloroprocaine', 'role': 'user'}, {'content': "Answer: D \nExplanation: Local anaesthetics with pKa value closest at physiological pH (7.4) will have a higher concentration of nonionized (unionized) base. Thus, the agent with pKa value away from physiological pH will have more concentration of ionized formChloroprocaine has highest pKa value, hence maximum ionized form at physiological pH.(Refer: Morgan and Mikhail's Clinical Anaesthesiology, 5th edition, pg no.268-270)", 'role': 'assistant'}]