Pharmacokinetics of cefepime in patients with respiratory tract infections.

The steady-state pharmacokinetics of cefepime were evaluated in 10 middle-aged and elderly patients with acute lower respiratory tract infections who were receiving 1 g intravenously every 12 h. One preinfusion and 15 postinfusion serum samples and total urine output were collected over one dosing interval between days 3 and 8 of therapy. Cefepime concentrations in serum over time exhibited a multicompartmental profile. Peak and trough concentrations in serum determined by a validated high-performance liquid chromatography method were 71.2 +/- 17.2 (mean +/- standard deviation) and 6.0 +/- 4.9 mg/liter, respectively. The steady-state volume of distribution was 0.22 +/- 0.05 liter/kg. Elimination half-lives ranged from 1.93 to 6.04 h (3.92 +/- 1.28 h), and total body clearances ranged from 36.9 to 102 ml/min per 1.73 m2 (73.0 +/- 19.7 ml/min per 1.73 m2). The disposition of cefepime at steady state in patients was comparable to previous observations in healthy elderly volunteers. The predictive performance of regression equations derived from single-dose studies in volunteers relating creatinine clearance with total body and renal clearances of cefepime exhibited slight biases (mean predictive errors, -9.7 and 2.1 ml/min per 1.73 m2, respectively) and similar precisions. Predicted and observed total body clearances (63.3 +/- 25.1 versus 73.0 +/- 19.7 ml/min per 1.73 m2, respectively) and renal clearances (51.3 +/- 24.4 versus 49.3 +/- 19.6 ml/min per 1.73 m2, respectively) were not significantly different. The pharmacokinetics of cefepime in infected patients appeared to be unaltered by illness, and the steady-state disposition of cefepime was predictable from data derived from single-dose studies in volunteers.