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

OBJECTIVE

To compare intra-articular (IA) and bone gentamicin concentrations achieved after intra-articular administration or regional intravenous perfusion (RIP).

STUDY DESIGN

Experimental study.

ANIMALS

Twelve healthy adult horses.

METHODS

Horses were assigned to 2 treatment groups (n = 6/group): Group 1, 1 g gentamicin administered simultaneously in both left and right metacarpophalangeal joints and group 2, 1 g gentamicin administered simultaneously in both left and right lateral palmar veins. Serum, synovial fluid, and bone biopsy specimens were collected. Gentamicin concentrations were determined by fluorescence polarization immunoassay. Bone, synovial fluid, and serum gentamicin concentrations were compared over time and between groups using 2-way ANOVA. Significance of all tests were evaluated at P <.05.

RESULTS

IA metacarpophalangeal joint administration resulted in higher concentration of gentamicin in synovial fluid than RIP administration. Synovial fluid concentration remained above minimum inhibitory concentration (MIC) for common pathogens for over 24 hours with IA and RIP administration. Bone gentamicin concentration remained above MIC for 8 hours with both methods; there was no significant difference in gentamicin concentration in bone with either method. Neither IA nor RIP administration had a significant effect on serum concentration of gentamicin.

CONCLUSIONS

In normal horses, there is no difference in bone gentamicin concentration obtained with IA or RIP administration.

CLINICAL RELEVANCE

Based on MIC for common equine pathogens, administration of gentamicin intra-articularly or by regional intravenous perfusion should be useful for treatment of osteomyelitis.