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Pharmacology · Beta blockers

Sotalol !

A beta blocker that also blocks potassium channels and lengthens the QT. Used for serious arrhythmias; it is started under ECG monitoring.

Updated 2026-11-01

  • Class: Beta blockers
  • Ion channel: hERG potassium channel (IKr) and β-adrenergic receptors
  • ATC code: C07AA07

The figure shows E-4031, a class III antiarrhythmic of the same methanesulfonanilide family, in the central cavity of the human hERG channel, where sotalol also acts; no structure with sotalol bound is available.

Target in 3D: hERG potassium channel (IKr) and β-adrenergic receptors. PDB structure 8ZYP (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Sotalol is given as a mix of two mirror-image forms. Both block the rapid delayed rectifier potassium current (IKr, the hERG channel), which lengthens the action potential and the refractory period in atria and ventricles (class III effect, seen as a longer QT). One form also blocks β1 and β2 receptors without selectivity (class II effect), slowing the heart and the AV node.

  1. Sotalol blocks the hERG potassium channel (IKr)
  2. The action potential and refractory period lengthen; QT gets longer
  3. It also blocks β receptors, slowing the sinus and AV nodes

Pharmacokinetics

Absorption
Almost completely absorbed by mouth
Metabolism
Not metabolised
Elimination
Excreted unchanged by the kidneys, so the dosing interval depends on creatinine clearance

Indications

  • Life-threatening ventricular arrhythmias
  • Keeping sinus rhythm in symptomatic atrial fibrillation or flutter Atrial fibrillation →

Adverse effects

Common

  • Fatigue
  • Bradycardia
  • Dizziness
  • Breathlessness

Contraindications

  • Sinus bradycardia, sick sinus syndrome or second- or third-degree AV block without a pacemaker
  • Congenital or acquired long QT syndrome
  • Low serum potassium
  • Cardiogenic shock or decompensated heart failure
  • Bronchial asthma

Key interactions

Class I or III antiarrhythmics and other drugs that prolong QT
Higher risk of torsades de pointes; avoided
Digoxin or calcium channel blockers
Bradycardia, hypotension and heart failure
Aluminium- or magnesium-based antacids
Lower sotalol absorption; doses are separated
Diuretics that lower potassium or magnesium
Low potassium raises the risk of torsades

What is monitored

  • QT interval on the ECG, continuously when starting
  • Creatinine clearance
  • Potassium and magnesium
  • Heart rate

Administration and safety

  • Started or restarted in a facility with continuous ECG monitoring and resuscitation available
  • Low potassium and magnesium are corrected before the first dose
  • Antacids with aluminium or magnesium are given at a different time
  • Products for atrial fibrillation and for ventricular arrhythmias have different labelling: the product is checked

Nursing care

  • Measure the QT on the ECG after doses as ordered and report prolongation
  • Check heart rate and blood pressure before each dose
  • Follow potassium, magnesium and creatinine, especially with diuretics, vomiting or diarrhoea
  • Teach the patient to report fainting, palpitations or a missed dose, and not to stop it abruptly

Pregnancy and breastfeeding

Human data are limited; it crosses the placenta and beta blockade may slow fetal growth and the newborn's heart rate, so it is used only if needed.

Test yourself

Think of the answer, then tap the question to see it.

Which two antiarrhythmic classes does sotalol belong to?

Class II (beta blockade) and class III (potassium channel block that prolongs repolarisation).

Why is sotalol started in hospital with continuous ECG?

QT prolongation can cause torsades de pointes and ventricular tachycardia, which must be caught and treated at once.

Why does kidney function decide how often sotalol is given?

Sotalol is excreted unchanged by the kidneys, so it accumulates when clearance falls.

Which electrolyte disturbance must be corrected before sotalol?

Low potassium (and magnesium), which increases the risk of torsades.

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← Back to the class: Beta blockers

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - SOTALOL HYDROCHLORIDE tablet (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 34 (McGraw Hill, 2023).

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Representative model, for educational purposes only.