Which of the following is 100 times more potent than morphine?: (A) Pethidine, (B) Fentanyl, (C) Pentazocin, (D) Meperidine
Answer is B. Fentanyl is 100 times more potent than morphine. Pethidine is 1/10th as potent as morphine. Ref KD Tripathi 8th ed.