Clinical Use:
Background: Gentamicin is an aminoglycoside antibiotic that is used primarily to treat serious infectious diseases caused by gram-negative bacilli. Gentamicin inhibits the normal process of protein synthesis in certain organisms. Gentamicin may be used in combination with other antibiotics to treat serious infections such as central nervous system infections (meningitis), urinary tract, respiratory tract, or gastrointestinal tract infections, and neonatal sepsis.

Most Streptococcus and some anaerobic organisms are resistant to gentamicin. Gentamicin has a narrow therapeutic range in serum of 5 to 10 mg/l (10.5 to 20.9 µmol/l) for peak levels and 1 to 2 mg/l (2.1 to 4.2 µmol/l) for trough levels.

Monitoring a patient’s serum gentamicin level is important in preventing drug-related side effects, which may occur when peak serum gentamicin levels exceed 10 to 12 mg/l (20.9 to 25.1 µmol/l) or when trough gentamicin levels exceed 2 mg/l (4.2 µmol/l). Because gentamicin shows an affinity for renal tissue and penetrates otoperilymph, excess gentamicin levels can cause renal toxicity and ototoxicity.

The elimination half-life of gentamicin is relatively short, approximately 2 to 3 hours. Therapeutic drug monitoring helps to ensure therapeutic levels and to minimize toxic accumulation of gentamicin.

Patients who are most susceptible to the toxic effects of gentamicin usually have impaired renal function, receive high doses, are critically ill neonates or undergo prolonged gentamicin therapy.

Reference Ranges: N/A
Associated Diseases:
Patient Preparation:
Specimen Requirements: Sample type

  • Serum or Heparinized Plasma
    • Do not use samples that have been stored at room temperature for longer than 8 hours.

Sample identification:

  • Three patient identifiers from
    • Name
    • D.O.B.
    • Address
    • N.H.S. number
    • Unit Number

    should match on the specimen and request form. This check may be performed prior to centrifugation by the Central Sort department.

Turnaround Time: 2 hours
Additional Information:
Referred Test: