Sotalol is a beta blocker that blocks the:

Appeared in: RIMS Nursing Officer - 2022

Explanation

Sotalol is classified as a Class III antiarrhythmic agent, which primarily works by blocking potassium channels (specifically the IKr current) in the heart.
This blockade prolongs the repolarization phase (Phase 3) of the cardiac action potential, thereby increasing the action potential duration and the effective refractory period.
Although the question identifies it as a beta-blocker (a Class II property), its key antiarrhythmic effect, especially for ventricular arrhythmias and atrial fibrillation, comes from its potassium channel blocking activity.
This dual action makes Sotalol unique among antiarrhythmic medications.

Option A: Sotalol does not primarily block calcium channels. This is the mechanism of Class IV antiarrhythmics.
Option C: Sotalol's therapeutic effect is not mediated by blocking magnesium channels. There are no specific 'magnesium channel blockers' used as antiarrhythmics.
Option D: Zinc channels are not a target for antiarrhythmic drug therapy. This option is medically irrelevant to the mechanism of Sotalol.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Mechanism of Action of Sotalol as background academic context rather than a clinical decision trigger.
The most critical nursing responsibility when administering Sotalol is monitoring for QT interval prolongation on the ECG, as this increases the risk of a life-threatening ventricular arrhythmia called Torsades de pointes.
Sotalol therapy must be initiated in a monitored setting where the patient's ECG and renal function can be closely watched. Baseline and follow-up ECGs are mandatory.
Nurses must monitor and help correct electrolyte imbalances, particularly hypokalemia (low potassium) and hypomagnesemia (low magnesium), as these conditions can worsen the risk of Sotalol-induced arrhythmias.

How to Approach the Question

First, identify the drug in the question: Sotalol.
Recall the classification of Sotalol. It is known as a beta-blocker, but it has a unique dual classification in the Vaughan Williams system.
Remember that Sotalol has both Class II (beta-blocker) and Class III (potassium channel blocker) properties.
The question asks what channel it blocks. The primary antiarrhythmic effect that distinguishes it and manages arrhythmias like AFib or VT is its Class III action.
Connect Class III action to its mechanism: blocking potassium channels.
Evaluate the options. 'Potassium channel of the heart' directly matches the Class III mechanism of action. The other options correspond to different drug classes or are incorrect.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 1 p. 1999-2001

E6 Pharmacology Katzung 16e p. 385-387

E6 Pharmacology Nursing Lilley 11e Part 2 p. 94-96

Practise the full RIMS Nursing Officer - 2022

Attempt every question from this paper in a timed mock, then review the full solution for each one.