Bone gentamicin concentration after intra-articular injection or regional intravenous perfusion in the horse.

This horse health study explains how two different methods of gentamicin administration – one intra-articular (directly into a joint) and the other regional intravenous perfusion (into a vein) – both prove to be effective in treating infections in joint and bone tissue of horses.

Objective of the Study

The researchers carried out an experimental study on 12 adult horses to examine the differences in gentamicin concentration in bone, synovial fluid and serum when administered through two different methods: intra-articular (IA), i.e., directly in the joints, and regional intravenous perfusion (RIP), or administered via the veins.

• The two groups of horses were administered gentamicin – group 1 within both left and right metacarpophalangeal joints and group 2 within both left and right lateral palmar veins.
• Serum, bone biopsy specimens, and synovial fluid samples from the horses were collected for analysis.

Methodology

The gentamicin concentrations in the samples were determined using a fluorescence polarization immunoassay. The variations in gentamicin concentration within bone, synovial fluid, and serum over time and between the two groups were compared using a statistical test known as 2-way analysis of variance (ANOVA). Any result that returned a P value less than .05 was considered statistically significant.

Results

• It was observed that the intra-articular administration of gentamicin resulted in a higher concentration of the antibiotic within the synovial fluid than regional intravenous perfusion did.
• The concentration of gentamicin remained above the minimum inhibitory concentration (MIC), which is the smallest amount of an antimicrobial that will inhibit the visible growth of a microorganism, for more than 24 hours in the synovial fluid for both methods of administration.
• In the bone tissue, the gentamicin concentration remained above MIC for 8 hours with either method, and there was no significant difference noted in the concentration in the bone between intra-articular and regional intravenous perfusion administrations.
• In terms of serum gentamicin concentration, neither method showed a significant difference.

Conclusion

The study concluded that both the intra-articular injection and regional intravenous perfusion methods are equally effective for achieving required gentamicin concentration in bone in horses. Given that gentamicin is able to maintain a concentration above the minimum inhibitory concentration for common equine pathogens, it can be a useful treatment for osteomyelitis, a bone infection, in horses. This result suggests that both methods are viable options for gentamicin administration in horses depending on the specifics of the case and the judgement of the treating veterinarian.