Effect of Dose on Intra-Articular Amikacin Sulfate Concentrations Following Intravenous Regional Limb Perfusion in Horses.
OBJECTIVE
To compare synovial concentrations of amikacin following intravenous regional limb perfusion (IVRLP) with two different doses, and to compare their ability to reach target concentrations for bacterial isolates from common orthopedic conditions.


METHODS
Randomized crossover experiment.


METHODS
Six adult horses.


METHODS
Horses received IVRLP with 2 and 3 g of amikacin in the cephalic vein of alternate limbs (20 minutes tourniquet application and ≥14 days washout period). Amikacin concentrations were quantified in synovial fluid collected from the middle carpal and metacarpophalangeal joints at 25 minutes, and 24, 36, and 48 hours after IVRLP. Minimum inhibitory concentrations (MIC) were determined from equine bacterial isolates and ability to reach target amikacin concentrations were compared.


RESULTS
Overall, middle carpal joint amikacin concentrations were higher following IVRLP with 3 g amikacin compared to 2 g (P=.031), with significant differences at 25 minutes (P=.002) and 24 hours (P=.021). No differences were observed between doses in the metacarpophalangeal joint (P=.267). Target amikacin concentrations for Staphylococcus aureus and coagulase-negative staphylococci were achieved in middle carpal and metacarpophalangeal joints at 25 minutes with both dosages and for Escherichia coli and Actinobacillus spp. in the middle carpal joint at 25 minutes with 3 g. Target concentrations were not achieved for Enterococcus spp, Pseudomonas spp, or Streptococcus equi ssp. zooepidemicus.


CONCLUSIONS
A 3 g amikacin dose is not justified in the majority of distal limb injuries, but should be reserved for isolates with an MIC higher than that achievable with a 2 g dose. Daily IVRLP may be necessary based on our results.
The William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, California.
Alison
A
Harvey
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, California. ikilcoyne@ucdavis.edu.
Isabelle
I
Kilcoyne
Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California.
Barbara A
BA
Byrne
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, California.
Jorge
J
Nieto
D000583:Amikacin / Q000008:administration & dosage* / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000378:metabolism; D050824:Carpal Joints / Q000098:blood supply; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D033023:Foot Joints / Q000098:blood supply; D006736:Horses / Q000378:metabolism*; D010477:Perfusion; D013582:Synovial Fluid / Q000737:chemistry*
D000900:Anti-Bacterial Agents; D000583:Amikacin