Equine Medicine & Surgery Intern Louisiana State University
Effect of Intra-Articular Morphine on the Antimicrobial Activity of Amikacin in Equine Synovial Fluid. McCurdy K1, Gull T2, Du X2, McCracken MJ1. 1University of Missouri, College of Veterinary Medicine, Columbia, MO; 2University of Missouri, Veterinary Medical Diagnostic Laboratory, Columbia, MO.
Septic arthritis is a common, painful, and expensive problem which is career- and life-threatening in horses. Cost-effective treatments are needed that decrease inflammatory damage without interfering with the efficacy of antibiotic therapy. Intra-articular morphine decreases pain and inflammation and has the potential to be a valuable adjunct therapy. Our objective was to investigate if morphine can be used within a joint without compromising coadministration of the antimicrobial amikacin. Synovial fluid from nine horses was collected just prior to, one hour, and 24 hours after intra-articular coadministration of amikacin and either morphine or saline. Modified Kirby-Bauer disk diffusion was used to evaluate the antimicrobial activity of the synovial fluid against Escherichia coli and Staphylococcus aureus. There were no significant differences in the sizes of the zones of inhibition between treatment groups against either bacteria. This showed that the efficacy of amikacin coadministered with morphine in a healthy equine joint was no different than the efficacy of amikacin alone. Intra-articular morphine has been shown to decrease inflammation and pain in sterile synovitis and may be a valuable therapy in infected joints. A limitation of the study was the sample size and the use of healthy joints with the antimicrobial efficacy evaluated in the laboratory. Intra-articular morphine could be a valuable therapeutic in the treatment of equine septic arthritis. Further research on the effects of intra-articular morphine in inflamed and septic equine joints is warranted.