TABLE 4

Pharmacokinetics, elimination constant, and half-life of the different β-lactam antibiotics and measured creatinine clearance

ParameteraMedian value for the parameter (IQR)b
FEP (n = 11)CAZ (n = 11)PIP (n = 89)MEM (n = 145)
Serum concn at CT (mg/liter)12.7 (10.0–18.5)24.9 (12.8–34.1)35.2 (23.2–56.2)9.1 (6.9–12.9)
Serum concn at T0 (mg/liter)6.9 (5.0–10.9)16.0 (5.7–20.7)7.0 (2.8–22.0)3.3 (2.0–3.2)
Serum concn at T2 (mg/liter)40.7 (35.4–48.3)42.0 (31.8–59.5)65.0 (45.5–83.7)12.0 (8.6–17.5)
%T >4× MIC34.5 (28.1–42.7)53.4 (34.8–73.8)34.2 (21.5–44.5)46.9 (33.0–60.7)
mCLCR (ml/min)155 (140–199)173 (155–226)186 (149–249)179 (146–231)
ke (h−1)0.3 (0.2–0.4)0.2 (0.2–0.3)0.5 (0.3–0.7)0.3 (0.2–0.3)
Half-life (h)2.5 (2.0–3.0)3.3 (2.2–4.2)2.2 (1.0–1.4)2.7 (2.2–3.4)
  • a CT, serum concentration at optimal period of time (i.e., at 40%, 50%, or 70% of the dosage interval of MEM, TZP, or FEP/CAZ, respectively); T0, trough; T2, 2 h after onset of the β-lactam infusion; %T >4× MIC, percentage of time during which the antibiotic remains above 4× MIC; mCLCR, measured creatinine clearance; ke, elimination constant.

  • b FEP, cefepime; CAZ, ceftazidime; PIP, piperacillin; MEM, meropenem; n, number of TDMs.