Amikacin pharmacokinetics in plasma and pleural fluid.

The pharmacokinetics of amikacin in plasma and pleural fluid were studied in nine adult patients with pleural effusions. After a single intravenous bolus of 7.5 mg of amikacin per kg, concentrations in plasma and pleural fluid were measured by fluorescence polarization immunoassays. Pleural fluid pH and PCO2 were also measured. The plasma pharmacokinetics was similar to other studies. However, in the present study the central compartment was significantly greater than the peripheral compartment. Our study suggested that there might be a significant binding of amikacin to the inflamed and/or damaged pleural as suggested by the significant correlations between the apparent volumes of distributions of central and total compartments with pleural fluid pH and PCO2. In pleural fluid, amikacin kinetics followed a large reservoir model with maximum concentration, 4.34 +/- 0.50 mg/L, occurring at 5.64 +/- 0.67 hours post-dose and its half-life was 13.50 +/- 2.93 hours. This concentration was lower than the minimal inhibitory concentration (MIC) for most of the sensitive strains of Gram-negative bacilli and therefore the antibiotics should be given as early as possible for gram-negative pneumonia.