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': 'Which anesthetic agent is contraindicated for intrathecal use? \nSelect and explain. \nA. Fentanyl, B. Remifentanyl, C. Sufentanil, D. AIfentanil', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]