Pharmacokinetics of enrofloxacin HCl-2H2O (Enro-C) in dogs and pharmacokinetic/pharmacodynamic Monte Carlo simulations against Leptospira spp.

Pharmacokinetic/pharmacodynamic (PK/PD) ratios of reference enrofloxacin (Enro-R) and enrofloxacin as HCl-2H2O (Enro-C), as well as Monte Carlo simulations based on composite MIC50 and MIC90 (MIC, minimum inhibitory concentration) vs. Leptospira spp., were carried out in dogs after their intramuscular (IM) or oral administration (10 mg/kg). Plasma determination of enrofloxacin was achieved by means of high-performance liquid chromatography. Maximum plasma concentration values after oral administration were 1.47 ± 0.19 μg/mL and 5.3 ± 0.84 μg/mL for Enro-R and Enro-C, respectively, and 1.6 ± 0.12 μg/mL and 7.6 ± 0.93 μg/mL, respectively, after IM administration. Areas under the plasma vs. time concentration curve in 24 h (AUC0-24) were 8.02 μg/mL/h and 36.2 μg/mL/h for Enro-Roral and Enro-Coral, respectively, and 8.55 ± 0.85 μg/mL/h and 56.4 ± 6.21 μg/mL/h after IM administration of Enro-R and Enro-C, respectively. The PK/PD ratios and Monte Carlo simulations obtained with Enro-C, not Enro-R, indicated that its IM administration to dogs will result in therapeutic concentrations appropriate for treating leptospirosis. This is the first time enrofloxacin has been recommended to treat this disease in dogs.