Pharmacokinetics of ampicillin in Alpacas (Lama pacos)

Abstract

Ampicillin is a betalactamic antibiotic of frequent use in human and veterinary medicine. Ampicillin pharmacokinetics was determined in 6 alpacas after intravenous and intramuscular injection of 15 mg/kg body weight. Serum concentrations were obtained by the microbiologic method, using Bacillus subtilis ATCC 6633 as the test microorganism. Results best fitted to a two compartment model. The pharmacokinetic parameters were (mean ± standard deviation): t ½a = 0,14 ± 0,08 and 0,35 ± 0,12 h; t½b= 0,60 ± 0,20 and 0,79 ± 0,52 h; Vd_ss = 0,63 ± 0,05 and 0,80 ± 0,25 l/kg; Cl_total = 15,96 ± 3,00 and 15,79 ± 2,89 ml/min/kg; AUC = 16,43 ± 3,44 and 17,22 ± 2,20 m g/ml*h for the i.v. and i.m routes, respectively. When administered by the i.m. route, t½_a = 0,05 ± 0,01 h; C_max = 18,38 ± 3,8 ug/ml and t_max = 0,16 ± 0,04 h. Bioavailability was 107 ± 20 %. No significant differences were found between parameters obtained for both routes of administration. Ampicilin achieved serum concentrations above the minimun inhibitory concentrations (MIC) against many gram positive veterinary pathogens up to 3,.5 hours after administration, with a rapid and complete absorption from the injection site and a short elimination half life.