Influence of fluid therapy on gentamicin pharmacokinetics in colic horses.

The aminoglycoside antibiotic gentamicin is commonly used in equine medicine for the prevention and treatment of Gram-negative and staphylococcal bacteria in surgically treated colic patients. The pharmacokinetics of gentamicin in these patients might be altered by the disease status, and/or under the influence of fluid therapy. The purpose of this study was to investigate the effect of intravenous fluid treatment on gentamicin kinetics in colic patients. Colic patients subjected to laparotomy were given fluid infusions according to clinical status. Following gentamicin administration, blood samples were taken for gentamicin analysis at different time points, and the main pharmacokinetic parameters including Vc, Vss, t(1/2) and MRT were calculated. Horses undergoing fluid therapy showed a significantly different t(1/2), clearance and MRT as compared to non-infused patients. However, taking into account the clinical status of the patients receiving fluid support, the data suggest that endotoxaemia, rather than fluid therapy, influence gentamicin pharmacokinetics following laparotomy.