Acebutolol (Sectral) is prescribed for dysrhythmias; what is the primary action?

• A. To block the beta1-adrenergic receptors in the cardiac tissues
• B. To increase the beta1-adrenergic receptors in the cardiac tissues
• C. To block the beta2-adrenergic receptors in the cardiac tissues
• D. To increase the flow of oxygen to the cardiac tissues

Answer: (A)

Blocking beta-1 adrenergic receptors in the heart is the primary action. By blocking these receptors, acebutolol dampens sympathetic stimulation of the heart, which slows the SA node’s firing, reduces conduction through the AV node, and lowers myocardial contractility. The result is a slower heart rate, slower AV conduction, and decreased automaticity, all of which help suppress tachyarrhythmias and stabilize the rhythm. This drug is cardioselective for beta-1 receptors, so its main effect is on the heart rather than the lungs; it does not increase receptor activity or directly increase oxygen delivery. Blocking beta-2 receptors could cause bronchoconstriction, which is not the desired effect for treating dysrhythmias.