Pharmacokinetic evaluation of beta-lactam antibiotics.

A simple method is proposed to predict free tissue concentrations of beta-lactam antibiotics from their plasma concentrations after iv bolus injection. During the elimination phase these free tissue concentrations exceed corresponding free plasma concentrations by a constant compound specific factor. This factor can be calculated from the different volumes of distribution (Vc, Vdss and Vdarea) and the plasma protein binding. Calculation of free tissue concentrations allows more secure interpretation of pharmacokinetic data with respect to in-vitro MICs for the comparison of different antibiotics or of the same antibiotic in different patient populations.