The Effects of Mepivacaine Hydrochloride on Antimicrobial Activity and Mechanical Nociceptive Threshold During Amikacin Sulfate Regional Limb Perfusion in the Horse.
Authors: Colbath Aimée C, Wittenburg Luke A, Gold Jenifer R, McIlwraith C Wayne, Moorman Valerie J
Journal: Veterinary surgery : VS
Summary
# Editorial Summary Intravenous regional limb perfusion (IVRLP) is a cornerstone technique for delivering high antibiotic concentrations to distal limb structures, but the joint pain associated with tourniquet application and drug delivery remains problematic in equine practice. Colbath and colleagues investigated whether adding mepivacaine (a local anaesthetic) to amikacin sulfate during IVRLP would provide analgesia without compromising antimicrobial efficacy, using nine healthy horses that received both treatment combinations (amikacin alone versus amikacin with mepivacaine) in a randomised crossover design, with synovial fluid sampling and mechanical nociceptive threshold testing at defined intervals. The critical findings showed that synovial amikacin concentrations and zones of inhibition against *Staphylococcus aureus* and *Escherichia coli* remained statistically equivalent between treatments at all timepoints; however, mechanical nociceptive thresholds were significantly elevated 30 minutes post-perfusion when mepivacaine was included (median 40.0 µg/mL compared to 19.5–15.3 µg/mL for amikacin alone). For practitioners performing IVRLP procedures, these results support the addition of mepivacaine to standard amikacin protocols as a means of reducing distal limb pain during and after treatment without sacrificing antimicrobial activity—a meaningful advance for patient welfare during what remains an uncomfortable procedure.
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Practical Takeaways
- •Adding mepivacaine to amikacin IVRLP provides pain relief without reducing antibiotic effectiveness, improving horse welfare during treatment
- •Clinicians can safely combine local anesthetic with antimicrobial agents during regional limb perfusion for infected joints
- •This approach may reduce post-treatment discomfort while maintaining therapeutic antimicrobial concentrations
Key Findings
- •Mepivacaine addition to amikacin IVRLP did not reduce synovial fluid amikacin concentrations or antimicrobial activity against S. aureus or E. coli
- •Mechanical nociceptive threshold increased significantly 30 minutes post-IVRLP with mepivacaine+amikacin (median 40.0 µg/mL) versus amikacin alone (median 19.5 µg/mL)
- •Combined mepivacaine-amikacin treatment provided analgesia without compromising antimicrobial efficacy