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Pharmacokinetics and milk levels of ceftriaxone were studied in healthy and endometritic cows following single intravenous administration. The drug was detected up to 8 h of dosing in plasma of healthy and endometritic cows and the drug disposition followed three-compartment open model. The values of Vd(area), AUC, t(1/2beta), Cl(B), MRT and P/C ratio were 0.50 +/- 0.19 L.kg(-1), 62.2 +/- 23.3 microg.ml(-1).h, 1.02 +/- 0.07 h, 0.30 +/- 0.09 L.kg(-1).h(-1), 1.55 +/- 0.25 h and 0.52 +/- 0.27, respectively, in healthy and 1.55 +/- 0.52 L.kg(-1), 37.0 +/- 17.1 microg.ml(-1).h, 1.56 +/- 0.25 h, 0.56 +/- 0.14 L.kg(-1).h(-1), 2.14 +/- 0.34 h and 1.44 +/- 0.60, respectively, in endometritic cows. The drug was detected in milk for 36 h after administration. For MIC(90) of 0.5 microg.ml(-1) the most appropriate dosage for ceftriaxone, would be 9.0 mg.kg(-1) repeated at 6 h intervals for the treatment of endometritis in cows.

The pharmacokinetics and urinary excretion of gatifloxacin were investigated after a single intravenous injection of 4 mg/kg body weight in buffalo calves. The therapeutic plasma drug concentration was maintained for up to 12 h. Gatifloxacin rapidly distributed from blood to tissue compartments, which was evident from the high values of the distribution rate constant, alpha1 (11.1 +/- 1.06 h(-1)) and the rate constant of transfer of drug from central to peripheral compartment, k12 (6.29 +/- 0.46 h(-1)). The area under the plasma drug concentration-time curve and apparent volume of distribution were 17.1 +/- 0.63 (microg.h)/ml and 3.56 +/- 0.95 L/kg, respectively. The elimination half-life (t (1/2 beta)), total body clearance (ClB) and the ratio of drug present in tissues and plasma (T/P) were 10.4 +/- 2.47 h, 235.1 +/- 8.47 ml/(kg.h) and 10.1 +/- 2.25, respectively. About 19.7% of the administered drug was excreted in urine within 24 h. A satisfactory intravenous dosage regimen for gatifloxacin in buffalo calves would be 5.3 mg/kg at 24 h intervals.

The disposition kinetics and urinary excretion of pefloxacin after a single intravenous administration of 5 mg/kg were investigated in crossbred calves and an appropriate dosage regimen was calculated. At 1 min after injection, the concentration of pefloxacin in the plasma was 18.95 +/- 0.892 microg/ml, which declined to 0.13 +/- 0.02 microg/ml at 10 h. The pefloxacin was rapidly distributed from the blood to the tissue compartment as shown by the high values for the initial distribution coefficient, alpha (12.1 +/- 1.21 h-1) and the constant for the rate of transfer of drug from the central to the peripheral compartment, K12 (8.49 +/- 0.99 h ). The elimination half-life and volume of distribution were 2.21+/- 0.111 h and 1.44 +/- 0.084 L/kg, respectively. The total body clearance (ClB) and the ratio of the drug present in the peripheral to that in the central compartment (P/C ratio) were 0.454 +/- 0.026 L/kg h) and 5.52 +/- 0.519, respectively. On the basis of the pharmacokinetic parameters obtained in the present study, an appropriate intravenous dosage regimen for pefloxacin in cattle for most of the bacteria sensitive to it would be 6.4 mg/kg repeated at 12 h intervals.