A teenager who ingested a large quantity of propranolol presents with refractory hypotension and bradycardia unresponsive to fluids, atropine, and dopamine. The antidote that bypasses the blocked receptor and restores myocardial contractility is:
- A Naloxone
- B Glucagon ✓
- C Flumazenil
- D Physostigmine
Correct answer: B. Glucagon
Explanation
Glucagon activates adenylate cyclase through its own G-protein-coupled receptor, independent of the beta-adrenergic receptor, raising intracellular cAMP and restoring inotropy and chronotropy despite complete beta-blockade. High-dose insulin euglycemic therapy is also used, but among the options given only glucagon acts downstream of the blocked receptor. Naloxone and flumazenil reverse opioid and benzodiazepine toxicity respectively and have no role here.
Reference: Goldfrank's Toxicologic Emergencies, 11th ed.
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