Pharmacokinetics and electrophysiological effects of sotalol hydrochloride in horses.
Authors: Broux B, De Clercq D, Decloedt A, Vera L, Devreese M, Gehring R, Croubels S, van Loon G
Journal: Equine veterinary journal
Summary
# Editorial Summary: Sotalol as an oral anti-arrhythmic in horses Horses with clinically significant arrhythmias have limited options for long-term pharmaceutical management, prompting investigation into sotalol—a β-blocker with class III anti-arrhythmic properties already established in human and small animal medicine. Broux and colleagues conducted a randomised, placebo-controlled cross-over trial in six unfasted Warmblood horses, administering oral sotalol at 2, 3, or 4 mg/kg bodyweight twice daily for nine days whilst measuring plasma concentrations, surface electrocardiography, echocardiography, and both atrial and ventricular monophasic action potential duration and effective refractory period. Mean steady-state plasma concentrations were dose-dependent (287–543 ng/mL across the three dosages), and sotalol significantly prolonged the QT interval and refractory periods in both atrial and ventricular tissue; notably, however, doubling the dose from 2 to 4 mg/kg did not produce a proportional increase in these electrophysiological parameters, suggesting a plateau effect. Cardiac function remained unaffected on echocardiography, and apart from transient local sweating, the drug was well tolerated across all dosages. These findings support sotalol's potential as a practical oral option for managing equine arrhythmias, though the plateau in electrophysiological response warrants consideration during clinical dosing; larger studies incorporating horses with naturally occurring arrhythmias would help establish optimal dosing regimens and long-term safety profiles.
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Practical Takeaways
- •Sotalol may provide a viable oral anti-arrhythmic treatment option for horses requiring long-term arrhythmia management, addressing a current gap in equine anti-arrhythmic therapy
- •Doses of 2-4 mg/kg twice daily appear safe and effective with minimal side effects, though dosing above 2 mg/kg may not provide additional electrophysiological benefit
- •Clinicians should monitor QT interval changes via electrocardiography when initiating sotalol therapy, but echocardiographic and other cardiac function measures appear unaffected
Key Findings
- •Oral sotalol at 2, 3, and 4 mg/kg twice daily achieved steady-state plasma concentrations of 287, 409, and 543 ng/mL respectively in unfasted horses
- •Sotalol significantly increased QT interval and effective refractory period (ERP) in right atrial and ventricular tissue
- •Higher dosages did not produce progressive increases in QT interval or ERP despite higher plasma concentrations, suggesting a plateau effect
- •No significant side effects were observed except transient local sweating, making sotalol a potential long-term anti-arrhythmic option for equine use