Anthelmintic Efficacy and Pharmacokinetics of Ivermectin Paste after Oral Administration in Mules Infected by Cyathostomins.
Authors: Bazzano Marilena, Di Salvo Alessandra, Diaferia Manuela, Veronesi Fabrizia, Galarini Roberta, Paoletti Fabiola, Tesei Beniamino, McLean Amy, Veneziano Vincenzo, Laus Fulvio
Journal: Animals : an open access journal from MDPI
Summary
Ivermectin is routinely administered to mules at equine-licensed doses despite evidence that donkeys—another equid—exhibit markedly different drug handling; this research addressed whether mules show similar pharmacokinetic divergence by treating fifteen naturally cyathostomin-infected animals with oral ivermectin paste at the standard equine dose of 200 µg/kg and measuring both blood concentrations and faecal egg count reduction over 28 days. Peak serum concentrations averaged 42.31 ng/mL occurring approximately 17 hours post-treatment, with an area under the curve of 135.56 ng·day/mL, whilst faecal egg count reduction remained consistently above 95% through day 28 using the modified McMaster technique. Although these efficacy figures appear robust, the pharmacokinetic profile warrants comparison with established equine data to determine whether dosage adjustments might optimise therapeutic outcomes or mitigate resistance risk in mule populations. Practitioners should recognise that mules may represent a distinct pharmacological entity, and extrapolating horse-derived dosing protocols without species-specific validation could compromise parasite control or promote anthelmintic resistance, particularly given the widespread use of ivermectin off-label in this population.
Read the full abstract on PubMed
Practical Takeaways
- •Horse-labeled ivermectin dosages appear effective in mules for cyathostomin control, maintaining >95% efficacy for at least 4 weeks post-treatment
- •Mules show different drug absorption and metabolism compared to horses (Tmax ~17 hours vs faster in horses), but this did not compromise clinical anthelmintic efficacy in this study
- •Practitioners should consider that off-label use of ivermectin in mules may warrant pharmacokinetic monitoring, as significant species differences exist despite successful treatment outcomes
Key Findings
- •Oral ivermectin paste at horse-recommended dosage (200 µg/kg) achieved maximum serum concentration of 42.31 ± 10.20 ng/mL in mules at 16.80 ± 9.96 hours post-treatment
- •Fecal egg count reduction remained >95% through day 28 post-treatment, indicating sustained anthelmintic efficacy against cyathostomins in naturally infected mules
- •Pharmacokinetic parameters in mules differ from horses despite using identical dosing protocols, suggesting need for species-specific dosing considerations