Pharmacokinetics and pharmacokinetic/pharmacodynamic integration of marbofloxacin in calf serum, exudate and transudate

Aliabadi, F. S., Lees, P. Pharmacokinetics and pharmacokinetic/pharmacodynamic integration of marbofloxacin in calf serum, exudate and transudate. J. vet. Pharmacol. Therap.25, 161–174. Marbofloxacin is a fluoroquinolone antimicrobial drug used in cattle for the treatment of respiratory infections. In this investigation the pharmacokinetics (PK) of marbofloxacin were determined after intravenous and intramuscular dosing at a dosage of 2 mg/kg. In addition the ex vivo pharmacodynamics (PD) of the drug were determined in serum and three types of tissue cage fluid (transudate, inflammatory exudate generated by carrageenan and exudate generated by lipopolysaccharide). Marbofloxacin PK was characterized by a high volume of distribution after dosing by both routes (1.28 L/kg intravenous and 1.25 L/kg intramuscular). Corresponding area under the concentration–time curve (AUC) and elimination half‐life (t½el) values were 9.99 and 10.11 μg h/mL and 4.23 and 4.33 h, respectively. Values of AUC for carrageenan‐induced exudate, lipopolysaccharide‐induced exudate and transudate were, respectively, 8.28, 7.83 and 7.75 μg h/mL after intravenous and 8.84, 8.53 and 8.52 μg h/mL after intramuscular dosing. Maximum concentration (Cmax) values were similar for the three tissue cage fluids after intravenous and intramuscular dosing. For in vivo PK data values of AUC: minimum inhibitory concentration (MIC) (AUIC) ratio for serum were 250 and 253, respectively, after intravenous and intramuscular dosing of marbofloxacin against a pathogenic strain of Mannheimia haemolytica (MIC=0.04 μg/mL). For all tissue cage fluids AUIC values were >194 and >213 after intravenous and intramuscular dosing, and Cmax/MIC ratios were 9 or greater, indicating a likely high level of effectiveness in clinical infections caused by M. haemolytica of MIC 0.04 μg/mL or less. This was confirmed by both in vitro (serum) and ex vivo (serum, exudate and transudate) measurements, which demonstrated a concentration‐dependent killing profile for marbofloxacin against M. haemolytica. Ex vivo, after 24‐h incubation, virtually all bacteria were killed (