Pharmacokinetics of Pradofloxacin in Loggerhead Sea Turtles ( Caretta caretta ) After Single Intravenous and Subcutaneous Injections

ABSTRACT Pradofloxacin is approved orally for dogs and cats and parenterally for cattle and pigs in the U.S. The objective was to determine the pharmacokinetics of pradofloxacin in loggerhead turtles ( Caretta caretta ) and whether the plasma concentration is sufficient to treat susceptible bacteria. Pradofloxacin (200 mg/mL, diluted to 20 mg/mL in sterile saline) 10 mg/kg was administered SC and IV to 16 yearling loggerhead turtles with sparse sampling blood collection. Plasma concentrations were measured via high‐pressure liquid chromatography (HPLC). Pharmacokinetic analysis was performed with nonlinear mixed effects modeling. After SC administration, the peak plasma concentration ( C MAX ) was 9.31 μg/mL and the elimination half‐life was 1.2 h, with bioavailability greater than 100%. After IV administration, the elimination half‐life was 1.3 h, systemic clearance was 0.74 L/kg/h, and volume of distribution was 1.36 L/kg. Pradofloxacin was tolerated IV and SC and well absorbed SC. Despite favorable absorption and C MAX values, the clearance was faster, and half‐life shorter, than other fluoroquinolones in turtles and pradofloxacin in mammals. These concentrations may not be sufficient to reach pharmacokinetic‐pharmacodynamic targets (AUC/MIC) for treating gram‐positive and gram‐negative bacteria in the susceptibility category of < 0.25 μg/mL, according to clinical breakpoints approved by the Clinical & Laboratory Standards Institute.