A B C D E F G H I J K L M N O P Q R S T U V W X Y Z #

Gentamicin Trough

Test Code
GENTAT


Alias/See Also
Garamycin


CPT Codes
80170

Preferred Specimen

Serum (gold top) tube



Minimum Volume
0.5 mL


Other Acceptable Specimens
Lithium Heparin Plasma (green top) tube or EDTA Plasma (purple top) Tube


Instructions

Collect a trough sample just before the next scheduled dose. When adjusting dosage, measure peak and trough levels during the same dosing intervals.



Transport Container

Lithium Heparin Plasma (green top), Serum (gold or red top) or EDTA Plasma (purple top) Tube



Transport Temperature
Room Temperature or Refrigeration


Specimen Stability
Room Temperature - 2 hours; Refrigerated - 7 days


Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis, Quantity Not Sufficient, IV contamination


Methodology
Photometric

Setup Schedule

Daily upon receipt



Report Available
Upon completion of analysis


Limitations
Concentrations of β-lactam antibiotics (penicillins and cephalosporins) at therapeutic levels may inactivate gentamicin in vivo and in vitro. Specimens from patients receiving β-lactam antibiotics (penicillins and cephalosporins) must be analyzed immediately upon collection or stored frozen to prevent in vitro inactivation of gentamicin. Trimethoprim at a concentration of 25 μg/mL (86 μmol/L) resulted in a positive bias of 0.57 μg/mL (1.2 μmol/L) at a gentamicin concentration of 5 μg/mL (10.8 μmol/L). Results for samples from patients receiving netilimicin or sisomicin, aminoglycosides structurally related to gentamicin, may be falsely elevated due to cross-reactivity in this assay (netilimicin, approximately 6% and sisomicin, approximately 7%).


Reference Range

Therapeutic Trough Range:

Birth - 1 Month:     0.5 - 1.0 ug/mL
1 Month - Adult:    0.0 - 2.0 ug/mL



Clinical Significance

Gentamicin is used in the treatment of serious infections caused by susceptible strains of gram-negative microorganisms and particular gram-positive organisms that are resistant to less toxic antibiotics.  Gentamicin is safe and effective only in a narrow range of concentrations for a given indication.  Exposure to high gentamicin concentrations for a prolonged period may cause renal impairment or ototoxicity.  Serum or plasma gentamicin measurements are used in the diagnosis and treatment of gentamicin overdose and in monitoring levels of gentamicin to ensure appropriate therapy.





The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.