Florfenicol, a monofluorinated analogue of thiamphenicol, has antibacterial activity against a broad spectrum of bacterial strains, including enteric bacteria that are resistant to chloramphenicol and thiamphenicol. The pharmacokinetics of florfenicol was studied following a single intravenous bolus or intramuscular injections at a dose of 20 mg/kg body weight, in five healthy goats. Serum florfenicol concentrations were determined using two analytical methods: microbiological assay and high-performance liquid chromatography (HPLC). Pharmacokinetic analysis was performed using redundant routine equations and the results derived from each method were compared. While florfenicol was detected for up to 4 and 8 h after administration by the bioassay, the drug was recovered in serum after 12 and 24 h by HPLC following intravenous and intramuscular injections, respectively. Comparison of the concentration profiles obtained by the two methods revealed substantial differences in the resultant kinetic data. Values for the initial serum concentration, elimination half-life, the area under the serum concentration-time curve, the mean residence time, and the systemic bioavailability were significantly (P < 0.01) higher when florfenicol concentrations were determined using HPLC. In conclusion, differences between analytical methodologies should be considered when interpreting the kinetic data for clinical use. However, both the hepatic biotransformations and the interchangeability of enantiomers need further investigation.

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The pharmacokinetics of danofloxacin was determined in five clinically normal adult female goats after intravenous (IV) or intramuscular (IM) doses of 1.25 mg/kg body weight. Blood and urine samples were collected from each animal at precise time intervals. Serum and urine concentrations were determined using microbiological assay methods and the data were subjected to kinetic analysis. After intravenous injection, the serum concentration time curves of danofloxacin were characteristic of a two-compartment open model. The drug was rapidly distributed and eliminated with half-lives of 17.71 +/- 1.38 min and 81.18 +/- 3.70 min, respectively. The drug persisted in the central, highly perfused organs with a K12/K21 ratio of 0.67 +/- 0.25. The mean volume of distribution at a steady state (Vdss was 1.42 +/- 0.15 L/kg. After intramuscular administration, the serum concentration peaked after 0.58 +/- 0.04 h at approximately 0.33 +/- 0.01 microg/ml. While danofloxacin could be detected in serum for 4 and 6 h, it was recovered in urine for up to 24 and 72 h after IV and IM administration, respectively. The systemic bioavailability after IM injection was 65.70% +/- 10.28% and the serum protein-bound fraction was 13.55 +/- 1.78%.

Summary Following a single i. v. injection of sulphadiazine, sulphadimidine and sulphathiazole in buffaloes (100 mg./kg. b. wt.), it was found that: 1. Sulphathiazole was the most rapidly eliminated, with a half‐life value of 198 min, followed by sulphadiazine (230 min); sulphadimidine had the slowest rate (563 min). The volumes of distribution of the 3 sulphonamides were 579, 751 and 452 ml./kg. b. wt., respectively. 2. 24 h after injection no detectable amount of sulphadiazine, but a significant amount of sulphathiazole (10.10 μg./ml.) and sulphadimidine (40.54 μg./ml.), was found in plasma. The protein‐bindung tendency of the 3 sulphonamides, as calculated in vitro, showed that values for sulphadiazine and sulphathiazole were very similar (18.01 and 16.62 %, respectively), while that for sulphadimidine (4.31 %), was much lower. 3. Excretion of the 3 sulphonamides in saliva was higher than in milk, with the concentration of sulphadimidine in both higher than that of the other 2 compounds. Very high concentrations of the parent sulphonamides and their acetylated derivatives were found in urine. Zusammenfassung Pharmakokinetik einiger Sulfonamide bei Büffeln Die einmalige i. v. Injektion von Sulfadiazin, Sulfadimidin oder Sulfa‐ thiazol bei je 3 Büffeln (100 mg/kg KGW) führte zu folgenden Ergebnissen: Sulfathiazol wurde am schneüsten eliminiert (HWZ 198 min), gefolgt von Sulfadiazin (230 min) und Sulfadimidin (563 min). Die Verteilungsvolumen der 3 Sulfonamide betrugen 579, 751 und 452 ml/kg KGW. 2. 24 h nach der Injektion ließ sich im Plasma kein Sulfadiazin mehr nachweisen, dagegen noch beachtliche Konzentrationen von Sulfathiazol (10,1 μg/ml) und Sulfadimidin (40,5 μg/ml). Die in vitro Bestimmung der Proteinbindung ergab ähnliche Werte für Sulfadiazin (18 %) und Sulfathiazol (16,6 %), während der Anteil beim Sulfadimidin wesentlich niedriger lag (4,3 %). 3. Die Ausscheidung der 3 Sulfonamide war im Speichel größer als in der Milch. In beiden Sekreten war die Konzentration von Sulfadimidin größer als die der beiden anderen Verbindungen. Hohe Konzentrationen der Ausgangssubstanzen und ihrer acetylierten Metaboliten ließen sich im Urin nachweisen. Résumé Pharmacocinétique de quelques sulfonamides chez des buffles Les résultats suivants ont été obtenus après une injection intraveineuse de Sulfadiazine, de Sulfadimidine ou de Sulfathiazol chez des buffles (100 mg/kg de poids): 1. Le Sulfathiazol fut éliminé le plus rapidement (demi‐temps 198 min) suivi par la Sulfadiazine (230 min) et la Sulfadimidine (563 min). Le volume de répartition des 3 sulfonamides fut de 579, 751 et 452 ml/kg de poids. 2. Aucune Sulfadiazine ne fut mise en évidence dans le plasma 24 h après l'injection, mais par contre des concentrations marquées de Sulfathiazol (10,1 μg/ml) et de Sulfadimidine (40,5 μg/ml) ont été constatées. La détermination in vitro de la liaison protéique a donné des valeurs identiques pour la Sulfadiazine (18 %) et le Sulfathiazol (16,6 %), cette valeur étant nettement plus basse pour la Sulfadimidine (4,3 %). 3. L...