Pharmacology · single question
A patient taking propranolol gets an anesthetic injection — what could happen?
Show answer and explanation
Correct answer: A. Epinephrine reaction (hypertensive crisis)
- A. Propranolol is a NON-SELECTIVE BETA-BLOCKER that blocks both β1 (cardiac) and β2 (vasodilatory) receptors. When epinephrine is injected (in local anesthetic), it stimulates α1 receptors (vasoconstriction) normally, but the β2-mediated vasodilation (which normally offsets the α1 effect) is BLOCKED by propranolol. The net result: UNOPPOSED α1 stimulation → SEVERE HYPERTENSION (hypertensive crisis) + possible reflex bradycardia. This is the classic epinephrine-propranolol interaction.
- B. While some beta-blockers lower BP, the ACUTE interaction with epinephrine in a propranolol patient causes HYPERTENSION (not hypotension) due to unopposed alpha stimulation.
- C. Propranolol can cause bronchospasm in asthmatic patients (by blocking β2 bronchodilation), but in this context the question asks about the INTERACTION WITH EPINEPHRINE specifically.
- D. The epinephrine-propranolol interaction is clinically significant — it is NOT without effect.