Gentamicin is an aminoglycoside antibiotic widely used in gram negative infections (i.e. Pseudomonas aeruginosa, Proteus sp., Escherichia coli, Klebsiella Enterobacter Serratia group, Citrobacter sp.) and some gram positive bacterial infections (Staphylococcus sp). Peak and trough levels are useful to assess adequacy of dosage regimen and to minimize the occurrence of ototoxicity and nephrotoxicity. Measurement of peak and trough levels every 2 3 days is imperative if the patient receives > 1.5 mg/kg for 10 days or more. Nephrotoxicity and ototoxicity may be more related to trough height dose frequency than to peak concentration. Variability in renal function, extracellular fluid volume, fever, anemia and concomitant administration with carbenicillin or lasix significantly affects individual levels.
Steady state drug levels are reached between 10 and 12 hours in adults and between 30 and 70 hours in children. Suggested sampling times are:
Peak |
IV |
30 - 60 min after dose |
Peak |
IM |
60 min after dose |
Trough |
IM & IV |
30 min before next dose |
Therapeutic range for trough levels is < 2 ug/mL and 4.0 - 8.0 ug/mL for peak levels.
Critical values are > 2.5 ug/mL for trough levels and > 13. 0 ug/mL for peak levels.
Specimen requirement is one plain red top tube of blood.
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