Plasma pharmacokinetics, tissue concentrations and urine elimination after cephalothin intravenous administration to cats under surgical conditions

Pharmacokinetic profile, tissue concentrations and urine elimination of cephalothin in cats under surgical conditions after a single intravenous dose (30 mg/kg) were studied. Initial plasma concentrations were high [Cp(0), 353.79±118.92 μg/mL], with fast and moderately wide distribution [T1⁄2(d) 0.14±0.10 h] [V(d(ss)) 0.19±0.03 L/kg] and rapid elimination (ClB, 0.16±0.03 L/h.kg; T1⁄2, 1.07±0.23 h; MRT, 1.16±0.21 h). Thirty to 60 minutes after intravenous administration, cephalothin tissue concentrations were in the range of 3.73 μg/g (testicle tissue) to 25.63 μg/g (uterus). Tissue/plasma concentrations rate was in a range of 0.04 (testicle) to 0.21 (uterus). Cephalothin urine elimination was 66.49% in the first 6 hours after administration. Cephalothin plasma concentrations remained above a MIC≥1 μg/mL up to 5.5 hours in all the studied cats. However, for MIC≥8 –μg/mL (MIC breakpoint) this time is reduced to 2.5 hours. This suggests that proper perioperative prophylactic use of cephalothin in cats requires a dose interval not longer than 2 hours.