Clinical Significance

Gentamicin is an aminoglycoside antibiotic which exhibits high potency and a broad spectrum bacterial action against both gram-negative and gram-positive organisms. Strong correlations have been shown between serum levels and both therapeutic effect and toxicity in specific patient types.

Peak serum levels of gentamicin in the range of 5-10 µg/mL are suggested for optimal therapeutic effectiveness. Persistently elevated peak concentrations (10 µg/mL) have been shown to cause renal and eighth cranial nerve toxicity. Nephrotoxicity takes the form of damage to the proximal renal tubules, and is associates with impaired renal function. Central nervous system toxicity is most often manifested as damage to the vestibular and auditory branches of the eighth cranial nerve.

Trough levels offer a more discrete indication of impending toxicity since they more closely correspond to tissue levels and are less affected by sampling errors. Slowly rising trough levels have been shown to correspond to tissue accumulation of the drug, and trough levels greater than 2 µg/mL have been associated with renal failure in some patients.