What is a potential adverse effect of esmolol in this setting?

• A. Hypotension
• B. Hyperkalemia
• C. Bradycardia
• D. Tachycardia

Answer: (C)

Esmolol blocks beta-1 receptors in the heart, which slows the firing of the SA node and slows conduction through the AV node. In a setting where you’re trying to rapidly control heart rate, the most likely adverse effect is bradycardia because the heart rate drops as the pacemaker and conduction pathways are suppressed. This can reduce cardiac output and potentially cause hypotension, so it requires careful titration and monitoring. The drug’s very short half-life (about 9 minutes) means any bradycardia is usually quickly reversible once the infusion is adjusted or stopped. Hyperkalemia isn’t a typical effect of beta-blockade, and tachycardia would be opposite the drug’s action, so it’s not expected.