This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthesia, Subject name: Pharmacology
[{'content': 'Most cardiotoxic local anaesthetic is: \nSelect and explain. \nA. Procaine, B. Bupivacaine, C. Prilocaine, D. Tetracaine', 'role': 'user'}, {'content': "Answer: B \nExplanation: - Bupivacaine is most cardiotoxic local anaesthetic - so, it is contra-indicated in intravenous regional anaesthesia (Bier's block) =Prilocaine caused methmoglobinemia", 'role': 'assistant'}]