Which category of medications includes agents that stimulate the sympathetic nervous system and may cause tachycardia?

• A. Beta-blockers
• B. Catecholamines
• C. ACE inhibitors
• D. Diuretics

Answer: (B)

Catecholamines act as direct stimulants of the sympathetic nervous system. They include agents like epinephrine and norepinephrine that bind to adrenergic receptors in the heart, especially beta-1 receptors. Activation of these receptors increases heart rate by boosting automaticity and conduction in the SA node, driven by higher cAMP levels that enhance pacemaker currents and calcium handling. That direct sympathetic stimulation is what leads to tachycardia. Other drug classes listed don’t act as sympathetic agonists: beta-blockers oppose this effect and tend to slow the heart; ACE inhibitors work on the renin‑angiotensin system; diuretics affect fluid balance and volume status, which can indirectly influence heart rate but not through direct sympathetic stimulation.