The Effects of Mepivacaine Hydrochloride on Antimicrobial Activity and Mechanical Nociceptive Threshold During Amikacin Sulfate Regional Limb Perfusion in the Horse.

This research explores how intravenous administration of drugs, specifically mepivacaine hydrochloride and amikacin sulfate, affects horses’ antimicrobial activity and pain response. The study concluded that using a combination of mepivacaine and amikacin did not reduce the antimicrobial effectiveness, while effectively increasing the horse’s pain threshold.

Experimental Procedure

• The study involved 9 healthy adult horses that were subjected to one of two treatments using the technique of intravenous regional limb perfusion (IVRLP).
• One treatment consisted of amikacin sulfate alone (1 g amikacin in 60 mL saline) while the other combined mepivacaine hydrochloride with the amikacin (1 g amikacin and 500 mg mepivacaine in 60 mL saline).
• Additionally, for empirical comprehensiveness, the experiment was ensured to have reciprocal treatments after intervals of a 24-hour wash-out period.

Monitored Variables

• The study was aimed at measuring the concentration of amikacin sulfate in the synovial fluid from middle carpal joints of the horses and monitoring its antimicrobial activity.
• In addition to this, the mechanical nociceptive threshold (MNT), essentially how the horses responded to pain, was also observed at multiple points before and after the IVRLP treatments and the application of a tourniquet.
• The effectiveness of this joint bacterial resistance and pain management was tested against Staphylococcus aureus and Escherichia coli infections.

Results of the Study

• In some instances, limbs had to be removed from the data set as they showed no detectable amikacin concentrations, leaving the researchers with 14 data sets to analyze.
• The concentration of amikacin sulfate in the synovial fluid and its effect in inhibiting bacterial infection remained consistent throughout, showing no significant variance between the treatments.
• On the other hand, in terms of altering pain sensitivity, there was a marked difference with the MNT showing a significant increase after the IVRLP procedure followed by tourniquet removal. This was more notable when using the combination of mepivacaine and amikacin (average range between 38.7-40 µg/mL) compared to amikacin alone (average range between 13.2-25.6 µg/mL).

Conclusions

• The study concludes that mepivacaine could be added to amikacin for IVRLP in horses, suggesting a viable means of not only maintaining the antimicrobial activity of the treatment involving amikacin alone, but also of providing improved analgesia or pain relief.