Pharmacokinetics and dosage regimen of levofloxacin in buffalo calves after single subcutaneous administration

The present study was conducted on six male buffalo calves to investigate the pharmacokinetics of levofloxacin following a single subcutaneous administration at the dose rate of 3 mg.kg(-1) body weight. Appreciable plasma concentration of levofloxacin (0.28 +/- 0.01 mu g.mL(-1)) was detected 2.5 min after injection and the peak plasma level of 2.94 +/- 0.07 mu g.mL(-1) was observed at 1 h. Drug levels of 0.28 +/- 0.01 mu g.mL(-1) in plasma were detected up to 12 h from administration. Rapid absorption of the drug was also evident by the high value of the absorption rate constant (2.53 +/- 0.53 h(-1)). The absolute bioavailability of levofloxacin after subcutaneous administration calculated on the basis of AUC (10.5 +/- 0.11 mu g.mL(-1).h) and Ke (0.272 +/- 0.009 h(-1)) after a single intravenous injection in buffalo calves was 44.3 +/- 1.76 per cent. The high value of AUC (8.02 +/- 0.2 mu g.mL(-1).h) reflected major exposure in the buffalo calves. Extensive distribution of the drug into various body fluids and tissues was reflected by the high value of Vd(area) (1.06 +/- 0.04 L.kg(-1)). The elimination half-life and MRT were 4.43 +/- 0.1 h and 6.71 +/- 0.17 h, respectively On the basis of the pharmacokinetic parameters, the calculated subcutaneous dosage regimen for levofloxacin in buffalo calves was 4.6 mg.kg(-1) at 24 h intervals.