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': 'Antiemetic acting on H2 receptors - \nSelect and explain. \nA. Promethazine, B. Metoclopramide, C. Ondansetron, D. Amiodarone', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Promethazine Promethazine is an antihistaminic antiemetic.", 'role': 'assistant'}]