[Determination of gentamicin in the serum of patients with normal renal function with the purpose of avoiding subtherapeutic antibiotic levels (author's transl)].

In 24 patients with normal renal function the serum concentration of gentamicin was checked during a period of 3--5 days. The biological test is simple and rapid to perform. The patients were given doses of 80--240 mg gentamicin per day. Even at doses of 240 mg/day no accumulation of the drug occurred. Intramuscular application of an 80 mg maximum dose of gentamicin did not result in any toxic serum concentrations. The measurement of peak concentrations--1 h after application--is therefore jus aimed at correcting too low dosages. The median values of the serum peak concentrations are 4--6 microgram/ml in the case of single dose application of 80 mg and 3 microgram/ml in the case of single dose application of 40 mg. Consequently serum concentrations effective against moderately susceptible bacteria (MIC = 1--4 microgram/ml) do not act for a sufficiently long time, since the half-life for elimination is 2 h. Daily dosages of up to 240 mg (3X80 mg) gentamicin are only effective in infections caused by very susceptible bacteria with a MIC up to 1 microgram/ml.