Possible influence of assay methods in studies of the pharmacokinetics of antibiotics.

In the present research, levels of gentamicin (GM) in serum and carrageenan pleural exudate from the rat have been compared, using three evaluation methods: microbiological assay (MA), enzyme-immunoassay (EMIT) and fluorescence-immunoassay (TDX). In a first study, the evaluations carried out by MA and EMIT have furnished comparable data in serum, while statistically significant differences were verified at all times in pleural exudate. On the contrary, in a second study, while the evaluations carried out by MA and EMIT, at all times and in both biological fluids, have produced similar data, the evaluation carried out by TDX consistently supplied higher results, with statistically significant differences at some times (5 min and 60 min for serum, 30 min and 60 min for exudate). Some possible interpretations of these results are discussed.