Abstract

Ceftiofur crystalline free acid (Excede^® Sterile Suspension) is a third generation cephalosporin designed for an extended duration of action. Excede^® is commonly used for treatment of various bacterial infections in pinniped rehabilitation medicine; however, pharmacokinetics has not been previously reported in these species. Ten California sea lions (Zalophus californianus), 6 males and 4 females ranging in weight from 18-62 kg were used for this pharmacokinetic study. A single dose of Excede^® was administered intramuscularly at 6.6 mg/kg, in the right or left pelvic limb muscles. The animals were being treated for various minor wounds or bacterial infections. Each animal was randomly assigned to two time points, with a total of 10 time points used in the study. Blood samples were collected at 6, 12, 24, 48, 72, 96, 120, 144, 168, and 192 hours following administration of the drug, and plasma was separated and stored at -80°C until analysis. An additional two animals, maintained under general anesthesia for other reasons, were used to collect blood at time points 1, 2, 3, 4, 5, and 6 hrs post-injection. Plasma drug concentrations were determined using a liquid chromatography with tandem mass spectrometry assay. The maximum plasma concentrations were observed 24 hours post-dose with a mean concentration of 3.6 µg/mL. These data indicate that a dose of 6.6 mg/kg would likely maintain a mean plasma drug level above 0.6 µg/mL for 5 days, and above 0.5 µg/mL for 8 days.

Acknowledgements

The authors wish to thank Carlos Rios for his laboratory and technical support during this study and the staff as well as the volunteers of The Marine Mammal Center for their care of the animals receiving antibiotic treatment.