Pharmacokinetics of cefepime in cystic fibrosis patients

The purposes of this study were to determine and compare the single- and multiple-dose pharmacokinetics of cefepime in patients with and without cystic fibrosis. Twelve patients with cystic fibrosis hospitalized for treatment of acute pulmonary exacerbations were studied. In addition, pharmacokinetic data for seven of the patients with cystic fibrosis were compared with those for seven age-matched control patients. The cefepime dose was 50 mg/kg of body weight (maximum, 2 g) administered as a 30-min intravenous infusion every 8 h for a minimum of 8 days. Serial plasma and urine samples, obtained after the first and last doses, were analyzed for cefepime content by a validated high-pressure liquid chromatographic assay. By standard noncompartmental analysis, the pharmacokinetic parameters ascertained were area under the concentration in plasma-time curve, elimination half-life, total body clearance, renal clearance, and volume of distribution at steady state. In addition, the maximum concentration in plasma was recorded. Mean (+/- standard deviation) results of the first dose analysis in patients with cystic fibrosis were as follows: maximum concentration in plasma, 142.6 (+/- 26.07) micrograms/ml; area under the concentration in plasma-time curve, 265.3 (+/- 114.31) micrograms.h/ml; elimination half-life, 1.8 (+/- 0.53) h; total body clearance, 127.2 (+/- 50.94) ml/min; renal clearance, 91.1 (+/- 38.86) ml/min/kg; volume of distribution at steady state, 14.1 (+/- 4.31) liters. Analysis for the last dose in patients with cystic fibrosis did not vary appreciably from these values, nor did those from the controls. Thus, it appears that the first-dose pharmacokinetics of cefepime are predictive of those at steady state. In order to consistently exceed the MIC for Pseudomonas aeruginosa for the entire dosing interval in patients with cystic fibrosis, a higher dose and/or different dosing interval compared with those used in this study may be necessary.