Which class of medications, when overdosed, is treated with glucagon IV?

• A. Nitrates
• B. ACE inhibitors
• C. Calcium channel blockers
• D. Beta-blockers

Answer: (D)

The main idea is that glucagon can reverse beta-blocker overdose by activating heart receptors that are not blocked by the beta-blocker. When beta-blockers overdose, they blunt heart rate and contractility, leading to bradycardia and low blood pressure. Glucagon provides an alternative way to stimulate the heart: it binds to glucagon receptors on cardiac cells and increases intracellular cAMP via adenylate cyclase, which raises calcium availability. This boosts heart rate and the strength of contractions regardless of beta-receptor activity, helping to improve perfusion and blood pressure.

That’s why glucagon IV is used in this scenario. It temporarily bypasses the blocked beta-adrenergic pathway to support the heart during overdose. It’s not a standard antidote for overdoses of nitrates, ACE inhibitors, or calcium channel blockers, whose toxic effects involve different mechanisms and require other treatments.