Which of the following is a major side effect of beta blockers?

• A. Bradycardia
• B. Tachycardia
• C. Hypertension
• D. Hyperglycemia

Answer: (A)

Blocking beta-adrenergic receptors in the heart slows the electrical activity of the SA node and reduces AV nodal conduction, producing a slower heart rate. This negative chronotropic effect is a defining feature of beta blockers, so bradycardia is a major and expected side effect. With a slower heart rate, cardiac output can drop, leading to fatigue, dizziness, or lightheadedness and possibly low blood pressure.

Tachycardia would be opposite to what beta blockers do, so it’s not a typical effect. Hypertension isn’t a side effect of beta blockers and is often one of the conditions these drugs are used to treat. Hyperglycemia isn’t a direct, common side effect; while beta blockers can affect glucose metabolism or mask hypoglycemia, hyperglycemia is not the characteristic concern here.