Single intravenous and multiple dose pharmacokinetics of gentamicin in healthy llamas

Abstract

Objective To determine the pharmacokinetics of gentamicin sulfate in healthy llamas after IV administration of a single bolus and after repeated parenteral administration. Design Prospective clinical trial. Animals 19 clinically normal, adult male llamas for the single-dose trial and 10 of the 19 llamas for the multiple-dose trial. Procedure In the first trial, llamas were given gentamicin (5 mg/kg of body weight, IV) as a single bolus, and serum gentamicin concentration was monitored over the next 48 hours. 2 months later, llamas were given gentamicin (2.5 mg/kg) IV for the first day, then IM every 8 hours for 7 days. Serum gentamicin concentration and indices of renal function and damage were monitored during the 7 days. Results There were no significant dose- or time-related differences in clearance of the drug; volume of distribution; apparent coefficients of the distribution and elimination phases, α and β, respectively; mean residence time; or distribution (t½α) and elimination phase (tt/2β) half-lives. The 5 mg/kg IV kinetic study revealed t½β, of 14.5 ± 5.06 minutes and t½β of 166 ± 20.5 minutes. The 2.5 mg/kg IV kinetic study revealed t½α of 17.7 ± 6.59 minutes and t½β of 165 ± 40.3 minutes. Peak serum gentamicin concentration averaged 10.10 μg/ml in the multiple-dose trial, and trough concentration averaged 1.50 μg/ml. Conclusions Dose effects were not observed for gentamicin clearance, volume of distribution, or half-lives. Multiple dosing at 2.5 mg/kg every 8 hours does not appear to cause renal impairment in healthy llamas. Clinical Relevance Gentamicin pharmacokinetic variables in llamas appear to resemble those in other ruminant species. (Am J Vet Res 1996;57:1193–1199)