PHARMACOKINETICS OF FLORFENICOL IN CEREBROSPINAL-FLUID AND PLASMA OF CALVES

Florfenicol, a fluorinated analog of thiamphenicol, is of great value in veterinary infectious diseases that formerly responded favorably to chloramphenicol. fn view of the treatment of meningitis in calves, we studied its pharmacokinetics in the cerebrospinal fluid (CSF) and pla sma of six animals. To this end, a new highperformance liquid chromato graphy method was developed which, unlike previous ones, uses solid-ph ase instead of double-phase extraction to isolate the drug, After a si ngle intravenous dose of 20 mg/kg of body weight, a maximum concentrat ion in CSF of 4.67 +/- 1.51 mu g/ml (n = 6) was reached, with a mean r esidence time of 8.7 h. The decline of florfenicol in both CSF and pla sma fitted a biexponential model with elimination half-lives of 13.4 a nd 3.2 h, respectively. Florfenicol penetrated well into CSF, as evide nced from an availability of 46% +/- 3% relative to plasma, The levels remained above the MIC for Haemophilus somnus over a 20-h period. Our results provide evidence indicating the effectiveness of florfenicol in the treatment of bacterial meningitis of calves.