Pharmacokinetics of intravenously and orally administered sotalol hydrochloride in horses and effects on surface electrocardiogram and left ventricular systolic function.
Authors: Broux B, De Clercq D, Decloedt A, De Baere S, Devreese M, Van Der Vekens N, Ven S, Croubels S, van Loon G
Journal: Veterinary journal (London, England : 1997)
Summary
Sotalol hydrochloride, a beta-blocker with class III antiarrhythmic properties used routinely in human and small animal medicine, has never been formally evaluated in equine patients despite the clinical need for effective chronic oral therapies to manage conditions such as atrial fibrillation and frequent ectopic beats. Researchers administered 1 mg/kg sotalol intravenously and orally to six healthy horses, measuring plasma drug concentrations, electrocardiographic changes (particularly QT interval prolongation), and left ventricular function via echocardiography. Oral bioavailability proved moderate at 48%, with peak plasma concentrations of 317 ng/mL achieved within 56 minutes and a half-life of approximately 15 hours—a pharmacokinetic profile suggesting once or twice-daily dosing might be feasible in clinical practice. The drug produced a significant dose-dependent QT prolongation without adverse effects on cardiac contractility or other measured electrocardiographic parameters, though transient sweating occurred following intravenous administration. These findings establish a pharmacological foundation for using sotalol in horses with chronic arrhythmias, though clinical efficacy and optimal dosing regimens for specific arrhythmia types require further investigation before widespread adoption in equine practice.
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Practical Takeaways
- •Sotalol may be a viable oral option for managing chronic equine arrhythmias, with intermediate bioavailability and a convenient 15-hour half-life supporting once or twice daily dosing protocols
- •The significant QT prolongation effect indicates sotalol works as expected in horses, but baseline and periodic ECG monitoring would be prudent to assess individual response and safety
- •Single-dose tolerance appears good in healthy horses, but this study was limited to acute administration in a small sample—clinical efficacy and long-term safety data for chronic use in arrhythmic horses are still needed
Key Findings
- •Oral bioavailability of sotalol in horses is intermediate at 48% with peak plasma concentration of 317 ng/mL compared to 1624 ng/mL after IV administration
- •Mean elimination half-life of sotalol in horses is 15.24 hours with maximal oral absorption occurring at 0.94 hours
- •Sotalol administration resulted in significant QT interval prolongation on electrocardiogram but no significant changes in other ECG or echocardiographic parameters
- •Single oral dose of 1 mg/kg sotalol was well-tolerated in healthy horses with only transient transpiration observed after IV administration and no adverse effects after oral dosing