Pharmacokinetics of amoxicillin/ciavulanic acid combination and of both drugs alone after intravenous administration to goats

The pharmacokinetic behaviour of an amoxicillin/clavulanic acid combination(25 mg kg⁻¹), and both drugs alone (amoxicillin 20 mg kg⁻¹), clavulanic acid 5 mg kg⁻¹), was studied after intravenous (i.v.) administration of single doses to 10 goats. The objective was to determine whether there were differences in the plasma kinetics of these drugs when administered in combination or alone. The plasma concentration-time data were analysed by compartmental pharmacokinetics and non-compartmental methods. The disposition curves for both drugs alone and in combination were best described by a biexponential equation (two-compartment open model). The elimination half-lives of amoxicillin were 1.05±0.09 h alone and 1.13±0.19 h in combination, and those of clavulanic acid were 0.87±0.07 h and 0.85±0.09 h, respectively. The apparent volumes of distribution of amoxicillin and clavulanic acid were similar in the two treatments. Body clearances of amoxicillin were 0.12±0.01 l h⁻¹ · kg alone and 0.11±0.01 l h⁻¹ · kg in combination, and of clavulanic acid were 0.12±0.02 l h⁻¹ · kg alone and 0.12±0.01 l h⁻¹ · kg in combination with amoxicillin. The half-lives and body clearances of amoxicillin and clavulanic acid did not differ significantly when administered alone and in combination. It was concluded that the ix. administration of amoxicillin and ciavulanic acid as a combination product did not alter the disposition kinetics of either drug.