Ciprofloxacin and norfloxacin pharmacokinetics and prostatic fluid penetration in dogs after multiple oral dosing

The aims of this study were to assess the pharmacokinetics and pharmacokinetic/pharmacodynamic (PK/PD) indices predictive of clinical outcome of ciprofloxacin (CIP) and norfloxacin (NOR) after multiple oral dosing, and to investigate their penetration into prostatic fluid in dogs. Eight dogs received seven oral doses b.i.d. of NOR (20 mg/kg) and CIP (15 mg/kg). Drug concentrations were determined in blood and in two prostatic fluid samples. Prostatic fluid concentrations were lower than plasma concentrations for both drugs. No statistically significant differences were determined between the pharmacokinetic parameters calculated after the first and seventh doses for either CIP or NOR. The PK/PD indices were found to be useful for predicting bacteriological outcome for fluoroquinolones (area under the disposition curve/minimum inhibitory concentration [MIC] and peak plasma concentration/MIC) and indicate that with this dose regimen CIP presents a more favourable disposition than NOR for successful clinical outcome.