Pharmacokinetics and milk penetration of moxifloxacin after intravenous and subcutaneous administration to lactating goats

The pharmacokinetics of moxifloxacin was studied following intravenous (IV) and subcutaneous (SC) administration of 5 mg/kg to healthy lactating goats (n = 6). Moxifloxacin concentrations were determined by high performance liquid chromatography assay with fluorescence detection. The moxifloxacin plasma concentration versus time data after IV administration could best be described by a two compartment open model. The disposition of SC administered moxifloxacin was best described by a one-compartment model. The plasma moxifloxacin clearance (Cl) for the IV route was 0.43 ± 0.02 L/kg (mean ± SE). The steady-state volume of distribution (Vss) was 0.79 ± 0.08 L/kg. The terminal half-life (t1/2λz) was 1.94 ± 0.41 and 2.98 ± 0.48 h after IV and SC administration, respectively. The absolute bioavailability was 96.87 ± 10.27% after SC administration. Moxifloxacin penetration from blood to milk was quick for both routes of administration and the high AUCmilk/AUCplasma and Cmax-milk/Cmax-plasma ratios reached indicated a wide penetration of moxifloxacin into the milk. From these data, it appears that a 5 mg/kg SC dose of moxifloxacin would be effective in lactating goats against bacterial isolates with MIC ⩽ 0.20 μg/mL in plasma and MIC ⩽ 0.40 μg/mL in milk.