Effects of an adapted intravenous amiodarone treatment protocol in horses with atrial fibrillation

• Published in: Equine veterinary journal Vol. 39; no. 4; pp. 344 - 349
• Main Authors: Clercq, D. de, Loon, G. van, Baert, K, Tavernier, R, Croubels, S, Backer, P. de, Deprez, P
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-07-2007
• Subjects: adverse effects; amiodarone; Amiodarone - administration & dosage; Amiodarone - adverse effects; Amiodarone - pharmacokinetics; Animals; Anti-Arrhythmia Agents - administration & dosage; Anti-Arrhythmia Agents - adverse effects; Anti-Arrhythmia Agents - pharmacokinetics; arrhythmia; atrial fibrillation; Atrial Fibrillation - drug therapy; Atrial Fibrillation - veterinary; chronic diseases; desethylamiodarone; Diarrhea - chemically induced; Diarrhea - veterinary; diarrhoea; Dose-Response Relationship, Drug; drug therapy; drugs; Echocardiography - veterinary; Echocardiography, Doppler, Color - veterinary; heart atrium; horse; horse diseases; Horse Diseases - drug therapy; Horses; Infusions, Intravenous - veterinary; intravenous injection; pharmacokinetics; quinidine sulphate; Treatment Outcome
• ISSN: 0425-1644; 2042-3306
• DOI: 10.2746/042516407X182811

Summary
Reason for performing study: Good results have been obtained with a human amiodarone (AD) i.v. protocol in horses with chronic atrial fibrillation (AF) and a pharmacokinetic study is required for a specific i.v. amiodarone treatment protocol for horses.
Objectives: To study the efficacy of this pharmacokinetic based i.v. AD protocol in horses with chronic AF.
Methods: Six horses with chronic AF were treated with an adapted AD infusion protocol. The protocol consisted of 2 phases with a loading dose followed by a maintenance infusion. In the first phase, horses received an infusion of 6.52 mg AD/kg bwt/h for 1 h followed by 1.1 mg/kg bwt/h for 47 h. In the second phase, horses received a second loading dose of 3.74 mg AD/kg bwt/h for 1 h followed by 1.31 mg/kg bwt/h for 47 h. Clinical signs were monitored, a surface ECG and an intra‐atrial electrogram were recorded. AD treatment was discontinued when conversion or any side effects were observed.
Results: Three of the 6 horses cardioverted successfully without side effects. The other 3 horses did not convert and showed adverse effects, including diarrhoea. In the latter, there were no important circulatory problems, but the diarrhoea continued for 10–14 days. The third horse had to be subjected to euthanasia because a concomitant Salmonella infection worsened the clinical signs.
Conclusion: The applied treatment protocol based upon pharmacokinetic data achieved clinically relevant concentrations of AD and desethylamiodarone.
Potential relevance: Intravenous AD has the potential to be an alternative pharmacological treatment for AF in horses, although AD may lead to adverse drug effects, particularly with cumulative dosing.