Effect of Dose on Intra-Articular Amikacin Sulfate Concentrations Following Intravenous Regional Limb Perfusion in Horses.
Authors: Harvey Alison, Kilcoyne Isabelle, Byrne Barbara A, Nieto Jorge
Journal: Veterinary surgery : VS
Summary
Intravenous regional limb perfusion (IVRLP) with amikacin is a cornerstone technique for treating equine orthopedic infections, yet optimal dosing remains unclear. Harvey and colleagues compared synovial fluid concentrations of amikacin in six horses receiving either 2 g or 3 g via IVRLP to the cephalic vein, sampling the middle carpal and metacarpophalangeal joints at multiple timepoints over 48 hours and cross-referencing results against minimum inhibitory concentrations from clinically relevant bacterial isolates. The 3 g dose achieved significantly higher concentrations in the carpal joint at 25 minutes and 24 hours post-perfusion, though no meaningful difference emerged in the metacarpophalangeal joint; importantly, both doses achieved target concentrations against *Staphylococcus aureus* and coagulase-negative staphylococci by 25 minutes, whilst the 3 g dose alone reliably covered *E. coli* and *Actinobacillus* spp. in the carpal joint. Neither dose produced therapeutic concentrations against *Enterococcus*, *Pseudomonas*, or *Streptococcus equi* ssp. *zooepidemicus*, and concentrations declined substantially by 48 hours. For practitioners, this suggests the standard 2 g dose suffices for common gram-positive joint infections, reserving 3 g for cases with confirmed susceptibility testing showing elevated MICs, and consideration should be given to repeated daily perfusions rather than single treatments to maintain therapeutic levels throughout infection resolution.
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Practical Takeaways
- •Use 2 g amikacin for most distal limb joint infections, as it achieves effective concentrations for common bacterial isolates (staphylococci); reserve 3 g dosing only for isolates with higher MICs confirmed by culture and sensitivity
- •Plan for daily IVRLP treatments for infections caused by Pseudomonas, Enterococcus, or S. equi zooepidemicus, as single-dose therapy cannot achieve adequate synovial concentrations
- •Perform bacterial culture and MIC testing early in joint infection cases to guide amikacin dosing decisions and treatment frequency
Key Findings
- •3 g amikacin dose achieved significantly higher synovial concentrations in middle carpal joints compared to 2 g at 25 minutes and 24 hours post-IVRLP (P≤0.021)
- •Both 2 g and 3 g doses achieved target concentrations for S. aureus and coagulase-negative staphylococci in carpal and metacarpophalangeal joints at 25 minutes
- •Only the 3 g dose achieved target concentrations for E. coli and Actinobacillus spp. in middle carpal joints at 25 minutes
- •Neither dose achieved target concentrations for Enterococcus, Pseudomonas, or S. equi ssp. zooepidemicus, suggesting daily IVRLP may be necessary