Pharmacokinetics of cefonicid in lactating goats after intravenous, intramuscular and subcutaneous administration, and after a long-acting formulation for subcutaneous administration

The single-dose disposition kinetics of cefonicid were determined in clinically normal lactating goats (n = 6) after intravenous (IV), intramuscular (IM) and subcutaneous (SC) administration of a conventional formulation, and after subcutaneous administration of a long-acting formulation (SC-LA). Cefonicid concentrations were determined by high performance liquid chromatography with ultraviolet detection. The concentration-time data were analysed by noncompartmental pharmacokinetic methods. Steady-state volume of distribution (V-ss) and clearance (Cl) of cefonicid after IV administration were 0.14 +/- 0.03 L/kg and 0.51 +/- 0.07 L/h center dot kg, respectively. Following IM, SC and SC-LA administration, cefonicid achieved maximum plasma concentrations of 14.46 +/- 0.82, 11.98 +/- 1.92 and 17.17 +/- 2.45 mg/L at 0.26 +/- 0.13, 0.42 +/- 0.13 and 0.83 +/- 0.20 hr, respectively. The absolute bioavailabilities after IM, SC and SC-LA routes were 75.34 +/- 11.28%, 71.03 +/- 19.14% and 102.84 +/- 15.155%, respectively. After cefonicid analysis from milk samples, no concentrations were found above LOQ at any sampling time. From these data, cefonicid administered at 20 mg/kg each 12 hr after SC-LA could be effective to treat bacterial infections in lactating animals not affected by mastitis problems.