Gentamicin serum concentrations: pharmacokinetic predictions.

Recent studies that emphasize the unpredictability of gentamicin serum concentrations have cast doubt on the accuracy of commonly used dosing nomograms. We therefore developed a digital computer program to evaluate gentamicin pharmacokinetics and have tested its ability to predict correctly gentamicin serum levels under clinical conditions. A significant relation (P less than .001) was found between 130 measured (bioassayed) and computer predicted levels from 40 patients. Serum levels were reliably estimated in patients with unstable renal function and were statistically, but not clinically, affected by changes in hematocrit. The calculation of volume of distribution on the basis of the patient's lean body weight rather than total body weight was an important factor that contributed to the accuracy of the predicted level. A new dosing chart is presented that incorporates the important variables affecting gentamicin pharmacokinetics into an easily used, convenient form.