Lung tissue concentrations and plasma pharmacokinetics of danofloxacin in calves with acute pneumonia.

Plasma and lung tissue pharmacokinetics of danofloxacin in calves with naturally induced acute pneumonia were determined in 2 separate studies. A maximal pneumonic tissue concentration of 1.17 micrograms/g was achieved 1.8 hours after IM injection of 1.25 mg of danofloxacin/kg of body weight. Pneumonic tissue danofloxacin concentrations were 5.5 times greater than those in plasma at 1 and 2 hours after injection. Cranioventral pneumonic tissue had significantly decreased danofloxacin concentration, compared with that of grossly normal tissue from the caudodorsal part of the lungs at 2 of 6 sample times. After IV injection, the apparent steady-state volume of distribution was 3.44 +/- 1.13 L/kg, and the elimination half-life was 6.26 +/- 2.27 hours. Maximal plasma danofloxacin concentration of 0.25 micrograms/ml was detected 0.80 hour after IM injection. Bioavailability was 91%. Our findings indicated that a large percentage of danofloxacin is rapidly absorbed after IM administration to calves with acute pneumonia. Extensive tissue penetration was suggested by a high steady-state volume of distribution and was indicated by high concentrations in pneumonic tissue.