Drug Monitoring

ITRACONAZOLE BIOASSAY

  • Test Code

    312

  • Clinical Significance

    The itraconazole bioassay test aids in monitoring antifungal therapy.

  • Methodology

    Bioassay

  • Limitations

    The result is not intended to be used as the sole means for clinical diagnosis or patient management decisions.

    • The bioassay is not accurate if the patient has taken another antifungal agent concurrently or within the prior week.
    • Concentration determined on a single specimen may not reflect future concentrations because of changes in adherence, drug dosage, route of administration, absorption, or receipt of other medication affecting absorption or metabolism of the azole.
  • Specimen Collection
    • Serum: Collect serum specimens in serum separator or red top tube. Allow blood to clot for 30 minutes, then centrifuge. Pipette serum into a plastic screw cap vial.
    • Plasma: Collect plasma specimens in an EDTA or heparin tube. Centrifuge for 15 minutes and pipette plasma into a plastic screw cap vial.
  • Minimum Specimen Requirements

    Serum/Plasma: 0.25 mL

  • Specimen Stability

    Room Temperature/Refrigerated/Frozen: 7 days

  • Specimen Rejection

    Any specimen type other than serum or plasma.

  • Transport Temperature

    Refrigerated/Frozen

  • Shipping

    Ship on dry ice or frozen cool pack for next day service. Monday – Friday delivery.

  • Turnaround Time

    Testing performed on Wednesday. Results released the next morning.

    Serum/Plasma: 2 days

  • Reference Range

    Therapeutic ranges have not been established, but levels of at least 3.0 µg/mL have been recommended for treatment. Lower concentrations (1 – 1.5 µg/mL) may be sufficient for prophylaxis.

  • Interpretative Information
    • None Detected: Reported when there is no zone of inhibition.
    • <0.3 µg/mL: Reported when the zone of inhibition is smaller than that of the lowest calibrator.
    • Positive: 0.3 – 20.0 µg/mL
    • >20.0 µg/mL: Reported when the zone of inhibition is greater than the highest calibrator.
  • Additional Information
    • Follow-up testing may be necessary if there are changes in treatment, including starting or stopping interacting medications, or suspicion of treatment failure.
    • Drug levels should be measured after treatment, of at least 2 weeks in dogs and 3 weeks in cats, to reach a steady state.
    • Preferable to collect blood sample at trough time.
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