Serum level monitoring of aminoglycoside antibiotics. Limitations in intensive care unit-related bacterial pneumonia.

Serum aminoglycoside assays have been accepted as useful methods of enhancing therapeutic efficacy in the treatment of intensive care unit-acquired pneumonia and in avoiding aminoglycoside nephrotoxicity. We prospectively studied 68 surgical patients with normal renal function and gram-negative bacterial pneumonia who were treated with aminoglycosides. Serum levels indicated subtherapeutic levels in 47 patients and verified optimum levels in 13 patients. Toxic trough levels developed in six patients and, despite immediate dosage adjustment, five patients suffered nephrotoxicity. Six additional patients also had nephrotoxicity. Five of these patients never had toxic peak or trough levels and rising trough levels developed in one patient after serum creatinine levels began to rise. We conclude that routine monitoring of serum levels effectively detects subtherapeutic antibiotic levels. This modality is useful for optimizing dosage schedules, but does not serve to predict or avoid nephrotoxicity in critically ill surgical patients.