Disposition of cefoxitin in patients with pleural effusion.

The pharmacokinetics of cefoxitin were studied in nine patients with pleural effusion of varied etiologies. All patients received a single intravenous bolus of 30 mg/kg. Cefoxitin levels were determined simultaneously in plasma and pleural fluid by means of a microbiologic plate diffusion method. The antibiotic follows a two-compartment open kinetic model. In the pleural fluid, maximum concentrations of cefoxitin of 19.72 +/- 9.72 microgram/ml were reached two hours after administration. The fraction of the antibiotic that reaches the pleural fluid represents 0.22% to 4.03% of the dose administered. The disappearance constant of the antibiotic from the pleural fluid is significantly smaller (Kd = 0.15 +/- 0.03 hours-1) than the elimination constant determined from the plasma levels (K13 = 2.27 +/- 0.90 hours-1). Cefoxitin was always found in antibacterial concentration in the pleural fluid for a considerable period of time.