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Test Code LAB1113 Gentamicin, Random, Plasma or Serum

Additional Codes

Test Name in EPIC EPIC Test Code Mnemonic
GENT RANDOM LAB1113 GENTR

 

Useful For/Utility

Gentamicin assay is used for the quantitative determination of gentamicin in human serum or plasma. The results obtained are used in the diagnosis and treatment of gentamicin overdose and in monitoring levels of gentamicin to help ensure appropriate therapy.

Methodology

Particle-Enhanced Turbidimetric Inhibition Immunoassay (PETINIA)

Clinical Information

Gentamicin is used in the treatment of serious infections involving aminoglycoside-sensitive organisms.

Monitoring gentamicin concentration in serum or plasma, along with careful clinical assessment, is the most effective means of ensuring adequate therapy. Gentamicin concentration correlates better with antibacterial activity than dosage. A standard dose of gentamicin does not always yield a predictable concentration because the drug’s concentration also depends on the patient’s volume of distribution and on the drug elimination. These factors are influenced by the mode of administration, the volume of extracellular fluid, renal retention, and physiological changes during therapy. Gentamicin has a narrow range of safe and effective concentration. Exposure to high concentrations for a prolonged period may cause renal impairment or ototoxicity. Patients with impaired renal function should be monitored closely while on gentamicin therapy because nephrotoxicity caused by gentamicin may be difficult to distinguish from symptoms of underlying renal disease.

Specimen Requirements

 Submit only 1 of the following specimens:

 

Preferred:

Specimen Type: Plasma

Container/Tube: Light-green top (lithium heparin gel)

Specimen Volume: 1 mL

Specimen Minimum Volume: 0.5 mL/pediatric: 0.2 mL in a green top MICROTAINER

Collection Instructions:

1. Spin down, separate from cells and aliquot within 2 hours of draw.

2. Draw level 8 hours after the END TIME of infusion. This will be used with 7 mg/kg or 5 mg/kg once daily dosing. If toxicity is suspected, draw level when ordered STAT.

3. Avoid repeated freeze/thaw cycles.

Additional Information:

1. Specimen should be analyzed in an appropriate period of time to assess dosing.

2. Label specimen appropriately (plasma).

3. For NEWBORN 3 POINT: 

           a. Q8 HRS: draw 6 hrs after infusion is complete.

           b. Q12 HRS: draw 8 hrs after infusion is complete.

           c. Q18 or  Q24 HRS: draw 12 hrs after infusion is complete.

4. For LOADING DOSE KINETICS: draw level 1 hr and 12 hrs after infusion is complete.

           a. NOTE: The 2nd and 3rd levels are subject to change based on the results of the 1st level and the patient's kidney function. Pharmacy will notify lab of any changes in times. A creatinine will be ordered separately if needed. NICU babies may also have some levels ordered for specific times - draw as ordered.  

 

Alternate:

Specimen Type: Serum

Container/Tube: Serum gel

Specimen Volume: 1 mL

Specimen Minimum Volume: 0.5 mL/pediatric: 0.2 mL in a red top MICROTAINER

Collection Instructions:

1. Spin down, separate from cells and aliquot within 2 hours of draw.

2. Draw level 8 hours after the END TIME of infusion. This will be used with 7 mg/kg or 5 mg/kg once daily dosing. If toxicity is suspected, draw level when ordered STAT.

3. Avoid repeated freeze/thaw cycles.

Additional Information:

1. Specimen should be analyzed in an appropriate period of time to assess dosing.

2. Label specimen appropriately (serum).

3. For NEWBORN 3 POINT: 

           a. Q8 HRS: draw 6 hrs after infusion is complete.

           b. Q12 HRS: draw 8 hrs after infusion is complete.

           c. Q18 or  Q24 HRS: draw 12 hrs after infusion is complete.

4. For LOADING DOSE KINETICS: draw level 1 hr and 12 hrs after infusion is complete.

           a. NOTE: The 2nd and 3rd levels are subject to change based on the results of the 1st level and the patient's kidney function. Pharmacy will notify lab of any changes in times. A creatinine will be ordered separately if needed. NICU babies may also have some levels ordered for specific times - draw as ordered.

Specimen Transport Temperature

Refrigerate 5 days/Ambient 8 hours OK/Frozen OK

Day(s) Test Set Up

Monday through Sunday

Performing Laboratory

Chemistry-

St. Joseph's Medical Center Lab

SMDC Clinical Lab

Fargo Hospital Lab

Test Classification and CPT Coding

80170

Reference Values

Therapeutic Range: 4.0-10.0 µg/mL

There are no established reference ranges for Gentamicin, Random.