THE DISPOSITION OF 5 THERAPEUTICALLY IMPORTANT ANTIMICROBIAL AGENTS IN LLAMAS

The disposition of five therapeutic antimicrobial agents was studied i n llamas (Lama glama) following intravenous bolus administration, Six llamas were each given ampicillin, tobramycin, trimethoprim, sulfameth oxazole, enrofloxacin and ceftiofur at a dose of 12 mg/kg, 1 mg/kg, 3 mg/kg, 15 mg/kg, 5 mg/kg, and 2.2 mg/kg of body weight, respectively, with a wash out period of at least 3 days between treatments, Plasma c oncentrations of these antimicrobial agents over 12 h following i.v. b olus dosing were determined by reverse phase HPLC. Disposition of the five antimicrobial agents was described by a two compartment open mode l with elimination from the central compartment, and also by non-compa rtmental methods, From compartmental analysis, the elimination rate co nstant, half-life, and apparent volume of distribution in the central compartment were determined. Statistical moment theory was used to det ermine noncompartmental pharmacokinetic parameters of mean residence t ime, clearance, and volume of distribution at steady state, Based on t he disposition parameters determined, and stated assumptions of likely effective minimum inhibitory concentrations (MIC) a dose and dosing i nterval for each of five antimicrobial agents were suggested as 6 mg/k g every 12 h for ampicillin: 4 mg/kg once a day or 0.75 mg/kg every 8 h for tobramycin; 3.0 mg/kg/15 mg/kg every 12 h for trimethoprim/sulfa methoxazole: 5 mg/kg every 12 h for enrofloxacin; and 2.2 mg/kg every 12 h for ceftiofur sodium for llamas, Steady-state peak and trough pla sma concentrations were also predicted for the drugs in this study for llamas.