In vitro and in vivo evaluation of ferric-hyaluronate implants for delivery of amikacin sulfate to the tarsocrural joint of horses.
Authors: Cribb Nicola C, Bouré Ludovic P, Hanna W J Brad, Akens Margarete K, Mattson Shawn E, Monteith Gabrielle J, Weese J Scott
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Ferric-hyaluronate implants for intra-articular amikacin delivery in horses Septic arthritis remains a significant challenge in equine practice, and sustained antimicrobial delivery to affected joints could theoretically improve outcomes whilst reducing systemic toxicity. Cribb and colleagues developed ferric-hyaluronate implants impregnated with amikacin sulfate and evaluated their performance both in laboratory conditions and in live horses, comparing them against conventional intra-articular injection. In vitro testing demonstrated that the implants maintained amikacin concentrations above 16 μg/mL (the threshold for inhibiting *Staphylococcus aureus*) for 8 days, successfully eliminated bacteria from synovial tissue samples, and caused no detectable damage to equine cartilage explants. However, the in vivo results proved disappointing: whilst implant placement initially achieved high synovial amikacin concentrations (141 μg/mL on average), levels dropped below therapeutic thresholds by 24 hours, whereas direct intra-articular injection sustained higher peak concentrations (378 μg/mL) and maintained therapeutic levels for 48 hours. The authors concluded that the implant design failed to translate promising laboratory results into clinically useful sustained release, making conventional injection—despite its shorter duration—the more reliable option for tarsocrural joint infections at present.
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Practical Takeaways
- •Ferric-hyaluronate implants as formulated in this study do not maintain therapeutic amikacin levels long enough for clinical use in tarsocrural infections—direct intra-articular injection remains superior
- •While the implant concept showed promise in laboratory conditions (effective bacterial killing, no cartilage damage), rapid elution in vivo makes it impractical for field use
- •Direct intra-articular antibiotic injection remains the gold standard for treating tarsocrural joint infections in horses based on this evidence
Key Findings
- •Amikacin-impregnated ferric-hyaluronate implants achieved concentrations >16 µg/mL in vitro and inhibited S. aureus growth for 8 days
- •In vivo amikacin concentration dropped below therapeutic level (<16 µg/mL) within 24 hours of implant placement, compared to 48 hours after direct intra-articular injection
- •Direct intra-articular amikacin injection demonstrated superior pharmacokinetics with peak concentration of 377.91 µg/mL versus 140.78 µg/mL for implants
- •Implants showed no adverse effects on cartilage explants and successfully eliminated bacteria from synovial tissue in vitro