Ten minutes after intravenous morphine 10 mg for postoperative analgesia, a patient develops flushing over the face and neck, intense pruritus, and a fall in systolic blood pressure from 120 to 80 mmHg. The anaesthetist switches the analgesic plan. Which alternative would least likely reproduce this reaction?
- A Morphine by slow infusion
- B Papaveretum
- C Fentanyl ✓
- D Pethidine
Correct answer: C. Fentanyl
Explanation
Morphine releases histamine from cutaneous mast cells, producing flushing, pruritus at the site of injection and along vein tracks, and venodilation with hypotension. Papaveretum and pethidine share significant histamine-liberating tendency. Fentanyl and its congeners cause minimal histamine release and are considered haemodynamically stable, making them the preferred choice in patients who react to morphine. This distinction is a standard viva and MCQ point in Indian exams.
Reference: KD Tripathi Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.