Abstract

The Marine Mammal Center is a rehabilitation facility that cares for roughly 500 ill and injured marine mammals each year, approximately 60% of which are California sea lions (Zalophus californianus). Ciprofloxacin is commonly administered at the center to California sea lion patients suffering from a variety of bacterial infections, yet pharmacokinetics of ciprofloxacin in pinnipeds have not been described. The objective of this study was to determine the half-life and plasma concentrations of ciprofloxacin at a commonly used dosage for pinnipeds.

An oral 10 mg/kg dose of ciprofloxacin was administered to 20 California sea lions. Blood was then collected at fixed time points (two time points per individual), and plasma ciprofloxacin concentrations were assessed via high-pressure liquid chromatography. A population pharmacokinetics model demonstrated that an oral ciprofloxacin dose of 10 mg/kg achieved an AUC of approximately 6 µg hr/mL and an elimination half-life of 3.1 hrs, which produces effective antibacterial exposure for only some of the bacterial organisms commonly isolated from infections in rehabilitating California sea lions.

Importantly, the AUC in this study is derived from the naïve pooled analysis and represents the mean for our sample population. Thus, for those individuals having concentrations below the target AUC, a 10 mg/kg dose of ciprofloxacin may result in treatment failure and may increase emergence of resistance. These data indicate that even for infections caused by highly susceptible bacteria, a 10 mg/kg oral dose of ciprofloxacin may not be effective in treating common bacterial infections in many individuals, and suggest a higher dose may be necessary.

Acknowledgements

The authors would like to thank the Riverbanks Zoo and Garden Conservation Support Fund for providing a grant that made this study possible. We would also like to thank the staff and volunteers at The Marine Mammal Center for their help in animal restraint and care during this study and Ms. Delta R. Dise of the Clinical Pharmacology Laboratory at North Carolina State University for her expertise in sample analysis.

* Presenting author