Plasma and Peritoneal Ceftriaxone Concentrations After Intraperitoneal Administration in Horses With Septic Peritonitis.

Intraperitoneal ceftriaxone administration in healthy horses results in high and prolonged peritoneal concentrations. Recent findings suggest that intraperitoneal ceftriaxone might increase survival rates in horses affected by peritonitis. The present study aimed to evaluate plasma and peritoneal concentrations of ceftriaxone after intraperitoneal administration in horses with septic peritonitis. Twenty-six horses presenting clinical, laboratorial, and sonographic findings compatible with the disease were included. All horses received daily intraperitoneal ceftriaxone (25 mg/kg bwt) in addition or not with other antibiotics and support therapies. High-performance liquid chromatography was used to determine plasma and peritoneal ceftriaxone concentrations before and after 12 and 24 hours of ceftriaxone administration. Mean plasma concentrations 12 and 24 hours after administration were, respectively, 1.84 ± 0.43 and 0.37 ± 0.07 μg/mL, and mean peritoneal concentrations were 5.7 ± 2.84 and 0.42 ± 0.13 μg/mL. Ceftriaxone concentration was lower in comparison with previous studies in healthy horses and presented under the minimal inhibitory concentration for enterobacteria (≤1 μg/mL) and for gram-positive isolates (≤0.5 μg/mL) at 24 hours. The variation of the results obtained between healthy horses and with septic peritonitis demonstrated that pharmacokinetics/dynamics are different between these patients and suggests the use of an interval of dose of 12 hours.