Mezlocillin in pleural effusions--analysis by HPLC.

Mezlocillin concentrations in the pleural fluid of six patients (42-76 years of age, suffering from cytologically confirmed malignant pleural effusions) were determined after intravenous infusion of 10 g mezlocillin. Serum and pleural fluid samples were withdrawn 15, 30, 45, 60 min, 2, 4, and 8 h post infusion. Detection of mezlocillin and its metabolites penicilloic acid and penilloic acid was carried out by means of high performance liquid chromatography (HPLC). Mezlocillin concentrations in serum increased up to 778 +/- 270 micrograms/ml after 15 min, steadily decreasing to 55 +/- 50 micrograms/ml (8 hours post infusion) comparable to the known pharmacokinetic behaviour of mezlocillin; in the pleural effusions mezlocillin levels increased up to 100 +/- 38 micrograms/ml after 1 h. This concentration was maintained throughout the following 7 h. Penicilloic levels ranged about 2-4% within serum, whereas levels below 1% were measured in the pleural fluid.