Pharmacokinetics of amoxicillin and cloxacillin following single dose intravenous and intramuscular administration in goats

A commercial preparation of Amoxicillin and Cloxacillin (1: 1), @ 10 mg/kg body weight was injected in goats by i.v. and i.m. routes of administration and the plasma time profile of amoxicillin and cloxacillin was studied. One and twocompartment model adequately described plasma-concentration time profile of amoxicillin and cloxacillin following single dose i.m. and i.v. administration, respectively. Cloxacillin levels were initially two-third of amoxicillin levels but were almost at par 2h post administration. Cloxacillin revealed faster absorption and distribution but slow elimination compared to amoxicillin. The volume of distribution and mean residence time (MRT) were also significantly higher for cloxacillin indicating better tissue distribution. Intramuscular route of administration proved to be superior as MRT and Vd(_area) were almost doubled as compared to intravenous administration. The bioavailability was 73% and 63% for amoxicillin and cloxacillin by intramuscular route, respectively. Based on the pharmacokinetic data, dosage regimen with an intravenous dose of 5.0 mg.kg^-1, while an intramuscular dosage regimen with a dose of 2.5 mg.kg^-1 at every 6 h interval was recommended for Amoxicillin. An intravenous dose of 20.5 mg.kg-1and an intramuscular dose of 15 mg.kg-1 at every 6 h interval is recommended for Cloxacillin in goats.