Sotalol Hydrochloride

Class III Antiarrhythmic Agent Beta-Adrenergic Receptor Blocker (Non-selective)

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 1-2 mg/kg (up to 3 mg/kg) q12h; for refractory arrhythmias, may increase to q8h q12h (or q8h for refractory cases) Duration: Long-term; adjust based on response and ECG monitoring
Notes: Start at lower end of dose range and titrate gradually. Monitor heart rate and QT interval. Use with caution in renal impairment.
Cat PO 1-2 mg/kg q12h q12h Duration: Long-term; adjust based on response
Notes: Cats may be more sensitive to beta-blockade; start at 1 mg/kg. Monitor for bradycardia and hypotension.
Horse PO 2-3 mg/kg q12h (for atrial fibrillation conversion, may use 3 mg/kg q12h) q12h Duration: For conversion: 2-4 days; for maintenance: long-term
Notes: Monitor ECG during conversion. Not recommended for horses with renal insufficiency.
Cattle PO 2-4 mg/kg q12h (extrapolated) q12h Duration: Limited data; use with caution
Notes: Not approved for food animals; observe withdrawal times.
Small Ruminants PO 2-4 mg/kg q12h (extrapolated) q12h Duration: Limited data; use with caution
Notes: Not approved; observe withdrawal times.
Rabbit PO Not established; use with caution Not established Duration: Not established
Notes: Limited data; consider alternative antiarrhythmics.
Bird/Poultry PO Not established Not established Duration: Not established
Notes: Limited data; not recommended.
Exotic/Other PO Not established Not established Duration: Not established
Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications
  • Management of ventricular and supraventricular tachyarrhythmias in small animals and horses
Dog (Canine)
  • Ventricular arrhythmias (e.g., ventricular premature complexes, ventricular tachycardia)
  • Atrial fibrillation (rate control and rhythm control)
  • Supraventricular tachyarrhythmias (e.g., atrial flutter)
  • Treatment of arrhythmias associated with dilated cardiomyopathy
Cat (Feline)
  • Ventricular arrhythmias
  • Hypertrophic cardiomyopathy (HCM) with arrhythmias
  • Atrial fibrillation (less common)
Horse (Equine)
  • Atrial fibrillation (conversion to normal sinus rhythm)
  • Ventricular arrhythmias
  • Supraventricular tachyarrhythmias
Cattle (Bovine)
  • May be used off-label for ventricular arrhythmias

Pharmacology & Mechanism of Action

Drug Class: Class III Antiarrhythmic Agent | Pharmacological Group: Beta-Adrenergic Receptor Blocker (Non-selective)

Mechanism of Action: Sotalol is a racemic mixture of d- and l-sotalol. It exerts its antiarrhythmic effects through two primary mechanisms: (1) non-selective beta-adrenergic blockade (both beta-1 and beta-2 receptors) and (2) prolongation of the cardiac action potential duration via inhibition of the delayed rectifier potassium current (IKr), which classifies it as a Class III antiarrhythmic. The beta-blocking action reduces heart rate, myocardial contractility, and atrioventricular (AV) conduction velocity, while the Class III action prolongs atrial and ventricular refractoriness, thereby suppressing reentrant arrhythmias. The d-isomer primarily contributes to the Class III effects, while the l-isomer provides both beta-blockade and Class III activity.

Pharmacodynamics: Sotalol produces dose-dependent prolongation of the QT interval and action potential duration in atrial and ventricular tissues. It increases the effective refractory period of the AV node, His-Purkinje system, and ventricular myocardium. Beta-blockade leads to decreased sinus node automaticity, reduced heart rate, and decreased myocardial oxygen demand. In dogs, sotalol has been shown to suppress ventricular arrhythmias and reduce the frequency of ventricular premature complexes. It also has a mild negative inotropic effect, which may be clinically significant in patients with compromised cardiac function.

⚡ Pharmacokinetics Summary

Absorption: Sotalol is rapidly and completely absorbed after oral administration in most species. In dogs, oral bioavailability is approximately 90-100%. Food can reduce the rate of absorption but not the extent. Peak plasma concentrations occur within 2-3 hours in dogs and 1-2 hours in cats.
Distribution: Sotalol is widely distributed throughout the body, with a volume of distribution of approximately 1.2-2.4 L/kg in dogs. It crosses the blood-brain barrier to a limited extent and is distributed into milk. Protein binding is low, approximately 0-10% in most species.
Metabolism: Sotalol undergoes minimal hepatic metabolism; it is not significantly metabolized by the liver. The majority of the drug is excreted unchanged in the urine. Therefore, hepatic dysfunction has little effect on its pharmacokinetics, but renal impairment can significantly reduce clearance.
Excretion: Sotalol is primarily eliminated unchanged by the kidneys via glomerular filtration and active tubular secretion. Renal clearance is approximately 70-80% of total clearance. In dogs, the elimination half-life is approximately 9-10 hours, while in cats it is around 7-8 hours. In horses, the half-life is shorter, approximately 4-6 hours.
Half-Life: Dog: 9-10 hours; Cat: 7-8 hours; Horse: 4-6 hours; Human: 12 hours
Bioavailability: Oral: ~90-100% in dogs; ~70-90% in cats; ~60-80% in horses
Protein Binding: Low (approximately 0-10%)

Available Formulations & Strengths

Oral Tablet 80 mg, 120 mg, 160 mg, 240 mg (PO)
Oral Solution (compounded) Various (e.g., 5 mg/mL, 10 mg/mL) (PO)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to sotalol or other beta-blockers
  • Sinus bradycardia (heart rate < 50 bpm in dogs, < 100 bpm in cats)
  • Second- or third-degree AV block (unless pacemaker in place)
  • Cardiogenic shock or decompensated heart failure
  • Prolonged QT interval (congenital or acquired)
  • Severe renal impairment (creatinine clearance < 30 mL/min) without dose adjustment
  • Asthma or bronchospastic disease (relative contraindication due to beta-2 blockade)
  • Uncontrolled diabetes mellitus (may mask hypoglycemia signs)
Warnings & Clinical Precautions:
  • Use with caution in patients with congestive heart failure; may exacerbate myocardial depression.
  • Do not discontinue abruptly; taper dose to avoid rebound tachycardia or arrhythmias.
  • Monitor ECG, heart rate, and blood pressure during therapy, especially when initiating or adjusting dose.
  • Use with caution in patients with renal insufficiency; reduce dose or extend dosing interval.
  • May mask signs of hypoglycemia in diabetic patients.
  • Use with caution in animals with a history of bronchospastic disease.
  • Safety in pregnant or lactating animals has not been established; use only if benefits outweigh risks.
  • In horses, monitor for signs of colic or gastrointestinal disturbances.
  • Avoid concurrent use with other QT-prolonging drugs (e.g., fluoroquinolones, macrolides, antihistamines).

Adverse Effects & Reactions

Common:

  • Bradycardia
  • Hypotension
  • Gastrointestinal upset (vomiting, diarrhea)
  • Lethargy or weakness
  • Proarrhythmia (new or worsened arrhythmias)

Serious / Severe:

  • Torsades de pointes (polymorphic ventricular tachycardia)
  • Congestive heart failure exacerbation
  • AV block or sinus arrest
  • Severe hypotension
  • Bronchospasm (in susceptible animals)

Rare:

  • Hepatotoxicity
  • Blood dyscrasias
  • Alopecia
  • Photosensitivity
  • Pulmonary fibrosis (long-term use)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Other beta-blockers (e.g., propranolol, atenolol) Additive beta-blockade leading to severe bradycardia, hypotension, and heart block. High
Calcium channel blockers (e.g., diltiazem, verapamil) Additive negative inotropic and chronotropic effects; risk of AV block and heart failure. High
Digoxin Additive effects on AV conduction; increased risk of bradycardia and arrhythmias. Moderate
QT-prolonging drugs (e.g., fluoroquinolones, macrolides, antihistamines, tricyclic antidepressants) Increased risk of torsades de pointes and ventricular arrhythmias. High
Diuretics (e.g., furosemide) Hypokalemia may increase risk of proarrhythmia. Moderate
Insulin or oral hypoglycemics Beta-blockade may mask signs of hypoglycemia and alter glucose metabolism. Moderate
Sympathomimetics (e.g., epinephrine, dobutamine) Antagonistic effects; may reduce efficacy of both drugs. Moderate

Overdose & Toxicity Management

Signs of Toxicity:

  • Severe bradycardia
  • Hypotension
  • Prolonged QT interval
  • Ventricular arrhythmias (including torsades de pointes)
  • Heart block
  • Cardiogenic shock
  • Seizures (in severe cases)

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Induce emesis if recent ingestion and animal is conscious. Administer activated charcoal to reduce absorption. Provide intravenous fluids for hypotension. Atropine may be used for bradycardia. Glucagon (50-150 mcg/kg IV) can be used to counteract beta-blockade effects. For refractory bradycardia or heart block, consider temporary cardiac pacing. For torsades de pointes, administer magnesium sulfate (30 mg/kg IV slowly) and consider isoproterenol or overdrive pacing. Monitor ECG and blood pressure continuously. In severe cases, hemodialysis may be considered (sotalol is dialyzable).

Food Animal Withdrawal Times

🥩 Meat: 7 days🥛 Milk: 3 days

Withdrawal times are not officially established for sotalol in food animals. The values provided are conservative estimates based on pharmacokinetic data and should be used with caution. Consult regulatory authorities for specific guidance. Extra-label use in food animals requires a valid veterinary-client-patient relationship and extended withdrawal times.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F); excursions permitted between 15-30°C (59-86°F).

Handling & Special Conditions: Protect from moisture. Keep in tightly closed container. Compounded oral solutions should be stored according to compounding pharmacy instructions, typically refrigerated and protected from light.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; approved for human use (Betapace, Betapace AF).

Extra-Label (Off-Label) Use: Sotalol is not FDA-approved for veterinary use; it is used extra-label in animals. In the US, extra-label drug use in food animals is permitted under AMDUCA (Animal Medicinal Drug Use Clarification Act) only with a valid veterinary-client-patient relationship, and must not result in violative residues. Withdrawal times must be extended accordingly. In non-food animals, extra-label use is common and accepted.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Sotalol is a valuable antiarrhythmic agent in veterinary medicine, particularly for the management of ventricular arrhythmias in dogs and atrial fibrillation in horses. It is often used when other antiarrhythmics (e.g., procainamide, quinidine) are ineffective or poorly tolerated. In dogs, sotalol is commonly used for arrhythmias associated with boxer cardiomyopathy and other myocardial diseases. It is important to perform a thorough cardiac evaluation (ECG, echocardiography) before initiating therapy. Dosage should be individualized based on renal function and response. Therapeutic drug monitoring is not routinely performed, but ECG monitoring is essential to assess QT interval and proarrhythmic risk. Sotalol should be used cautiously in animals with pre-existing heart failure or renal impairment. In horses, sotalol is used for atrial fibrillation conversion, but success rates vary; it may be combined with other agents. Always consider potential drug interactions and adverse effects. Client education should include signs of toxicity (e.g., weakness, collapse, seizures) and the importance of not abruptly discontinuing the medication.

References & Literature

  • 📚 Plumb's Veterinary Drug Handbook
  • 📚 Papich Veterinary Pharmacology and Therapeutics
  • 📚 Compendium of Veterinary Products (CVP)