Which of the following is a potential adverse effect of beta blockers?

• A. Hyperglycemia
• B. Bradycardia
• C. Bronchodilation
• D. Hyperkalemia

Answer: (B)

Beta-1 blockade in the heart slows the firing of the SA node and reduces conduction through the AV node, so the heart rate drops. This direct effect makes bradycardia the most likely adverse effect when using beta blockers, especially in patients with preexisting conduction issues or on other heart-suppressing drugs. Bronchodilation would come from beta-2 activation, but beta blockers block beta-2 receptors, which can actually worsen bronchospasm in susceptible individuals. Hyperglycemia is not the typical direct adverse effect—beta blockers can alter glucose metabolism and mask hypoglycemia, but they don’t commonly cause overt hyperglycemia as the primary issue. Hyperkalemia is possible in some contexts due to changes in beta-2–mediated potassium uptake or renin-angiotensin activity, but it is not the classic adverse effect; the most consistent and expected issue is bradycardia.