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tobramycin in serum/plasma

Indications: - therapeutic drug monitoring, tobramycin therapy Reference values: - Peak Values: 4.0-8.0 ug/mL - Trough Values: 0.0-2.0 ug/mL Clinical significance: - Tobramycin is primarily active against staphylococci & gram-negative bacilli - often used in the treatment of urinary tract infection, pneumonia, & gram-negative sepsis - when sepsis is suspected, especially in burn patients, aminoglycosides remain an important part of prophylaxis - two reasons for measuring serum aminoglycoside antibiotics a) to assure the physician that the patient is receiving enough of the antibiotic to be effective against the infecting bacteria b) to make sure that the dose received by the patient is maintained below the toxic limit* *see tobramycin for adverse effects (toxicity) Principle: The TOBRA pack is used in the DuPont ACA discrete clinical analyzer to quantitatively measure tobramycin in serum & plasma. It is an adaptation of Syva's homogeneous enzyme immunoassay technique, EMIT. The reagents used in this methodology are matched lots of tobramycin antibody & the tobramycin - glucose-6-phosphate dehydrogenase conjugate. The concentration of tobramycin determines the amount of tobramycin - glucose-6-phosphate dehydrogenase (TOBRA-G6PD) conjugate that is bound to the antitobramycin antibody. The unbound conjugate catalyzes the oxidation of glucose-6-phosphate, with the simultaneous reduction of NAD to NADH, more rapidly than does the bound conjugate. The rate of increasing absorbance at 340 nm due to the increase in NADH is related to the concentration of tobramycin by means of a calibration curve or a mathematical function. Specimen: Patient preparation: No special patient preparation is required. Collect blood samples by venipuncture following established good laboratory practices. If the sample is obtained through the infusion set, flush the line thoroughly with saline before taking the blood sample. With some exceptions, any anticoagulant may be used to collect plasma for analysis. Serum, as well as plasma, may be used for most assays. If is very important that the physician be informed of the times of sample collection & dose administration; this information should be supplied to the laboratory with each sample & reported with the results of each test. Samples derived from blood should be refrigerated upon collection & stored frozen (-20 degrees Celsius or colder) if not analyzed within 24 hours. Complete mixing of each thawed sample is required before analysis.

Related

tobramycin (Nebcin, Tobrex)

Specific

tobramycin free in serum/plasma tobramycin in serum/plasma peak tobramycin in serum/plasma random tobramycin in serum/plasma trough

General

therapeutic drug measurement

References

  1. ACA IV Discrete Clinical Analyzer Instrument Manual, Volume 1: Operation, DuPont Company, Wilmington, Delaware, 1984.
  2. ACA IV Discrete Clinical Analyzer Instrument Manual, Volume 3B: Chemistry, DuPont Company, Wilmington, Delaware, 1984.
  3. Tobramycin Laboratory Test Directory ARUP: 90270
  4. Tobramycin Peak Laboratory Test Directory ARUP: 90315
  5. Tobramycin Trough Laboratory Test Directory ARUP: 90320