A patient with a history of asthma and borderline blood pressure needs perioperative opioid analgesia. Morphine produces flushing, hypotension, and bronchospasm in this setting. Which property of morphine accounts for these effects, and which alternative avoids them?

• A Mast cell histamine release; fentanyl is the appropriate alternative ✓
• B Ganglionic blockade; alfentanil is the appropriate alternative
• C Central vagal stimulation; remifentanil is the appropriate alternative
• D Complement activation; sufentanil is the appropriate alternative

Explanation

Morphine and pethidine directly liberate histamine from cutaneous mast cells, causing venodilation, hypotension, urticaria, and provocation of bronchospasm in asthmatics. Fentanyl and its congeners do not release histamine appreciably and therefore provide hemodynamic stability, making fentanyl the standard choice when histamine effects must be avoided. The reaction is pharmacologic histamine release rather than true allergy, so skin testing is generally unnecessary.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

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