Tobramycin, Serum, Peak

Tobramycin is cleared by the kidney, and accumulates in renal tubular cells. Nephrotoxicity is most closely related to the length of time that trough levels are >2 μg/mL. Creatinine levels should be monitored every two to three days as this serves as a useful indicator of impending renal toxicity. The initial toxic result is nonoliguric renal failure that is usually reversible if the drug is discontinued. Continued administration of tobramycin may produce oliguric renal failure. Nephrotoxicity may occur in as many as 10% to 25% of patients receiving aminoglycosides; most of this toxicity can be eliminated by monitoring levels and adjusting dosing schedules accordingly. Aminoglycosides may also cause irreversible ototoxicity that manifests itself clinically as hearing loss. Aminoglycoside ototoxicity is relatively uncommon and clinical trials where levels were carefully monitored and dosing adjusted failed to show a correlation between auditory toxicity and plasma aminoglycoside levels. In situations where dosing is not adjusted, however, sustained high levels may be associated with ototoxicity. This association is far from clear cut, and new once-daily dosing regimens (and associated high peak serum concentrations) that fail to enhance toxicity further complicate this issue.