This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
[{'content': 'Most potent analgesic: \nSelect and explain. \nA. COX-2 inhibitor, B. Remifentanil, C. Morphine, D. Sufentanil', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ref: Goodman & Gillman 13th ed. P 376* Fentanyl citrate and sufentanil citrate are congeners of fentanyl and are considered as potent analgesics* After systemic delivery:# Fentanyl is about 100 times more potent than morphine# Sufentanil is about 1000 times more potent than morphine* Time to peak analgesic effect after IV administration: 5 minutes* These drugs are well known to be used as epidural analgesic.', 'role': 'assistant'}]