[Comparative pharmacokinetics of piperacillin in young and elderly subjects]

One single 4 g dose of piperacillin was administered by intravenous infusion over 30 min to 15 patients aged from 66 to 90 years (mean +/- s.e.m.: 79.8 +/- 2.0 years); the patients mean weight was 53 +/- 4 kg. Fifteen samples of blood were withdrawn from each subject. Plasma piperacillin levels were measured by high performance liquid chromatography with detection in ultraviolet light at 214 nm. Mean plasma piperacillin concentrations in elderly subjects, measured 0.5, 2 and 12 h after dosing, were 168.5 +/- 15.7, 79.9 +/- 11.5 and 1.72 +/- 0.69 microgram.ml-1, as against 146.8 +/- 10.6, 35.5 +/- 3.9 and 0.212 +/- 0.040 microgram.ml-1 in healthy young adults. Plasma piperacillin concentrations versus time curves obtained after the infusion was discontinued were bi-exponential, with half-lives T1/2 (lambda 1) and T1/2 (lambda 2) of 0.65 +/- 0.11 and 1.72 +/- 0.09 h respectively; the corresponding figures in young adults were 0.59 +/- 0.03 and 1.81 +/- 0.13 h respectively). In elderly subjects the mean total clearance of piperacillin (ClT = 2.90 +/- 0.25 ml.min-1.kg-1) was reduced by 15% (NS) and the volume of distribution during steady state (Vdss = 0.337 +/- 0.027 L.kg-1) was increased by 43% (P less than 0.001). As a result, the mean time of piperacillin stay in the body (MRS = Vdss/Cl) was practically doubled in elderly subjects (2.09 +/- 0.15 h as against 1.15 +/- 0.04 h in young adults (P less than 0.01).