Effects of an adapted intravenous amiodarone treatment protocol in horses with atrial fibrillation.
Authors: De Clercq D, van Loon G, Baert K, Tavernier R, Croubels S, De Backer P, Deprez P
Journal: Equine veterinary journal
Summary
# Editorial Summary: Intravenous Amiodarone for Equine Atrial Fibrillation Chronic atrial fibrillation in horses presents a significant clinical challenge, and whilst intravenous amiodarone has shown promise in human medicine, equine-specific dosing protocols were lacking. De Clercq and colleagues evaluated a pharmacokinetically-derived two-phase amiodarone infusion protocol in six horses with chronic AF, administering a high loading dose (6.52 mg/kg/h for 1 hour) followed by extended maintenance infusion (1.1 mg/kg/h for 47 hours), with an optional second cycle. Half the treated horses converted to normal sinus rhythm without complications; however, the remaining three experienced adverse effects—predominantly gastrointestinal disturbance lasting 10–14 days—and failed to convert, with one animal requiring euthanasia due to concurrent Salmonella infection. Despite achieving therapeutically relevant drug concentrations, the protocol demonstrated that intravenous amiodarone, whilst potentially valuable for AF management, carries a significant risk of cumulative toxicity and gastrointestinal side effects in equine patients. Clinicians considering this treatment should weigh the 50% conversion rate against the substantial risk of prolonged diarrhoea and ensure robust infection control measures, particularly given the documented interaction with enteric pathogens in this population.
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Practical Takeaways
- •Intravenous amiodarone is a potential treatment option for equine atrial fibrillation but carries a 50% failure rate and significant risk of gastrointestinal adverse effects requiring careful monitoring
- •If using intravenous amiodarone, expect possible diarrhoea lasting 1-2 weeks; watch for signs of secondary bacterial infection (e.g., Salmonella) which can complicate the clinical picture
- •Success cannot be predicted in advance; close ECG monitoring and clinical observation are essential, and treatment should be discontinued immediately if adverse effects develop
Key Findings
- •50% of treated horses (3/6) successfully cardioverted to normal sinus rhythm without adverse effects using the adapted intravenous amiodarone protocol
- •50% of treated horses (3/6) failed to convert and experienced adverse effects, primarily diarrhoea lasting 10-14 days
- •The pharmacokinetic-based protocol achieved clinically relevant concentrations of amiodarone and its active metabolite desethylamiodarone
- •Cumulative dosing of intravenous amiodarone in horses carries risk of adverse drug effects despite achieving therapeutic drug concentrations