Polymyxin B protects horses against induced endotoxaemia in vivo.
Authors: Barton M H, Parviainen A, Norton N
Journal: Equine veterinary journal
Summary
# Editorial Summary: Polymyxin B in Equine Endotoxaemia Endotoxaemia remains a significant clinical challenge in equine practice, and identifying safe, cost-effective interventions is crucial for improving outcomes in this potentially fatal condition. Barton and colleagues experimentally induced endotoxaemia in 24 healthy horses and assessed whether polymyxin B (PMB)—an antibiotic known to bind endotoxin—could ameliorate clinical signs when given either before or after endotoxin administration at two different doses (5000 or 1000 units/kg). Horses receiving 5000 u/kg PMB, whether given 30 minutes before or after endotoxin challenge, demonstrated significantly reduced fever, heart rate elevation and serum tumour necrosis factor levels compared to untreated controls, with pre-treatment showing the greatest protective effect; notably, the lower 1000 u/kg dose proved less effective. Renal function, assessed via urine gamma-glutamyltranspeptidase:creatinine ratios, remained unaffected, suggesting PMB was well-tolerated without inducing nephrotoxicity in this model. These findings support PMB as a viable therapeutic option for managing endotoxaemia in clinical cases, with the added advantage that treatment can provide benefit even when initiated after endotoxin exposure, though cautious use remains warranted in azotaemic patients where renal function is already compromised.
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Practical Takeaways
- •Polymyxin B can be used as a therapeutic option for endotoxaemia in horses, with the advantage that it remains effective even when given after clinical signs appear
- •A dose of 5000 u/kg is more effective than 1000 u/kg for controlling fever, heart rate elevation, and inflammatory markers in endotoxic horses
- •While nephrotoxicity was not observed in this controlled study, caution is still warranted in horses with existing azotaemia or renal compromise before using polymyxin B
Key Findings
- •Polymyxin B at 5000 u/kg administered before or after endotoxin significantly reduced fever, tachycardia, and serum TNF compared to saline controls
- •Polymyxin B was effective even when administered 30 minutes after endotoxin infusion began
- •No significant nephrotoxicity was demonstrated by urine GGT:creatinine ratio changes in this model
- •The 5000 u/kg dose showed greater protective effects than the 1000 u/kg dose