Tarsocrural joint polymyxin B concentrations achieved following intravenous regional limb perfusion of the drug via a saphenous vein to healthy standing horses.

The study investigates if therapeutic levels of polymyxin B, administered through intravenous regional limb perfusion to horses, are achieved in the tarsocrural joint and any potential adverse effects. It suggests that this method could be a potential treatment for horses with synovial infections caused by gram-negative bacteria.

Introduction and Methods

• The research was focused on determining whether therapeutic concentrations of polymyxin B (PB) could be reached in the tarsocrural joint of horses when it was given through intravenous regional limb perfusion (IV-RLP) using a saphenous vein.
• The methods involved nine healthy adult horses and two separate experiments.
  • Experiment One: Six horses each got 25 and 50 mg doses of PB by IV-RLP via a saphenous vein. There was a gap of at least two weeks between treatments. The application of the drug further involved the use of two tourniquets.
  • Experiment Two: Four horses each received 300 mg of PB by IV-RLP in a manner identical to the first experiment.
• Samples of blood and tarsocrural joint fluid were taken to measure the PB concentration before and after the administration of the drug at predetermined times.

Results

• For all three doses, it was found that the average synovial fluid PB concentration was > 10 times the therapeutic concentration and declined below the level of quantification at 30 and 1,440 minutes after administration of the drug.
• No adverse systemic or local effects were observed following the administration of PB.

Conclusions

• The results indicated that treatment using IV-RLP of PB could be a viable alternative treatment for synovial infections caused by gram-negative bacteria in horses.