Specimen Information

Type

Gold, SST

Volume

1.0 ml

Transport Info

Refrigerated
48 hour stability

Fasting Required?

False

Clinical Significance

Used in the diagnosis and treatment of gentamicin overdose and in monitoring levels of gentamicin to ensure proper therapy.

Gentamicin is an aminoglycoside antibiotic that exhibits high potency and a broad-spectrum bacterial action against both gram-negative and gram-positive organisms. It exhibits a narrow therapeutic index that makes its use hazardous, especially in patients with impaired renal function. Therefore, accurate monitoring of the serum level in such patients is mandatory. In addition, the dose-serum level profile curve of gentamicin has been found to be surprisingly unpredictable, both in terms of peak-serum levels and elimination half-life from plasma. 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 to 10 mg/mL are suggested for optimal therapeutic effectiveness. Persistently elevated peak concentrations (10 mg/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 associated 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 mg/mL have been associated with renal failure in some patients.