Since the majority of bacterial infections are extracellular, optimisation of the antimicrobial drug concentration at the site of infection, e.g. the interstitial fluid, is important to reach a successful therapeutic effect.
The in vitro plasma protein binding of pradofloxacin was determined to be 36-37% in dogs and 29-31% in cats 12
Percentage bound pradofloxacin in plasma of dogs and cats:
pradofloxacin concentrations (ng/ml)
Given at 3mg/kg, the unbound drug concentration of pradofloxacin peaked at 1.55 μg/ml in the interstitial fluid, while in serum the maximum concentration was 1.85 μg/ml 13. Considering the plasma protein binding of pradofloxacin in dogs (36 – 37%), the unbound drug serum concentration (1.85-36% = 1.18) is actually lower than the active drug concentration in the interstitial fluid (1.55 µg/ml).
In the interstitial fluid, the maximal drug concentration of pradofloxacin exceeded aprox. 13 to 103-fold the MIC90 values of 0.015 to 0.12 µg/ml for the bacterial pathogens Pasteurella multocida, Escherichia coli and Staphylococcus pseudointermedius. 14.
Peak concentrations detected at the site of infection after oral administration of pradofloxacin at 3 mg/kg exceed the MIC90 values for mentioned SPC bacterial pathogens. Based on ISF-related PK/PD ratios good clinical efficacy against the bacteria listed in the Veraflox SPC can be predicted.