Comparative pharmacokinetic analysis of amoxycillin using open two and three-compartment models

The pharmacokinetic characteristics of amoxycillin were studied in healthy volunteers after intravenous injection of 250 mg, 500 mg and 1,000 mg, and infusion of 2 g and 5 g. Serum concentrations were fitted using either bi- and tri- exponentional equations. Comparison of the regression curves obtained revealed that the three-compartment model gave a better fit to the serum concentration versus time curve. It was evident that there was a third, slow, dose dependent phase of disposition. This result has been confirmed by the fact that the terminal half life of amoxycillin on cessation of a comtinuous infusion is significantly greater than after acute administration.