Administration of tobramycin and gentamicin by the intravenous route every 6 hr in patients with normal renal function.

The feasibility and safety of administration of tobramycin and gentamicin in every 6 hr rather than every 8 hr was studied in 18 patients with normal renal function. Eleven patients received tobramycin in a dose of 1.0-3.2 mg/kg every 6 hr, and seven received gentamicin in a dose of 1.4-2.0 mg/kg every 6 hr. The mean peak serum concentrations, excluding the levels in the three children given tobramycin, were 5.5 and 5.8 mug/ml in each group, respectively, after maximal dosage; trough levels 2 hr before the next dose were less than or equal to 1.8 mug/ml in both groups of patients. Neither drug accumulated in the serum when the dosage regimen was maintained for three to 19 days. There was no evidence of nephrotoxicity or ototoxicity. Administration of tobramycin and gentamicin every 6 hr seems to be a reasonable program for patients with normal renal function, pending further studies on safety.