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Test Code YITCON Itraconazole, Serum

Additional Codes

YITCON

Reporting Name

Itraconazole, S

Useful For

Verifying systemic absorption of orally administered itraconazole

 

Patients with life-threatening fungal infections

 

Patients considered at risk for poor absorption or rapid clearance of itraconazole

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum Red


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube: Red top (serum gel/SST are not acceptable)

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial within 2 hours of collection.


Specimen Minimum Volume

0.18 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Red Refrigerated (preferred) 29 days
  Ambient  29 days
  Frozen  29 days

Reference Values

ITRACONAZOLE (TROUGH):

>0.5 mcg/mL (localized infection)

>1 mcg/mL (systemic infection)

 

HYDROXYITRACONAZOLE:

No therapeutic range established; activity and serum concentration are similar to parent drug.

Day(s) Performed

Monday through Friday; Saturday

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80189

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ITCON Itraconazole, S 10989-2

 

Result ID Test Result Name Result LOINC Value
81247 Itraconazole, S 10989-2
5122 Hydroxyitraconazole 18337-6

Clinical Information

Itraconazole is a synthetic triazole antifungal drug approved for treatment and prophylaxis of a variety of fungal infections. Its activity results from inhibition of fungal synthesis of ergosterol, an integral component of fungal cell membranes.

 

Concerns about adequate absorption and drug interactions are some of the major indications for therapeutic drug monitoring. Mean oral bioavailability approximates 55% but is highly variable; absorption can be enhanced by food or acidic drinks. Hepatic enzyme inducers can cause low serum itraconazole levels, and coadministration of these drugs has been associated with itraconazole therapeutic failure.

 

Itraconazole therapeutic efficacy is greatest when serum concentrations exceed 0.5 mcg/mL for localized infections or 1.0 mcg/mL for systemic infections. An active metabolite, hydroxyitraconazole, is present in serum at roughly twice the level of the parent drug. These concentrations refer to analysis by high-performance liquid chromatography; quantitation by bioassay generates considerably higher apparent drug measurements due to reactivity with the active metabolite.

Interpretation

A lower cutoff concentration has not been defined that applies in all cases. The serum concentration must be interpreted in association with other variables, such as the nature of the infection, the specific microorganism, and minimal inhibitory concentration results, if available. Localized infections are more likely to respond when serum itraconazole is more than 0.5 mcg/mL (by high-performance liquid chromatography); systemic infections generally require drug concentrations more than 1.0 mcg/mL. Consider target of more than 1.5 mcg/mL for itraconazole plus hydroxyitraconazole. Therapeutic drug monitoring should be done at steady state, which usually occurs in about 7 days. Timing of the serum collection is not as critical due to the drug's long half-life, but trough collections are recommended.

Cautions

Enteropathy, H2-histamine receptor blockers, hepatic enzyme inducers, and other variables can result in low to non-detectable serum levels with concomitant high risk of therapeutic failure.

 

Patients with AIDS and organ transplant recipients receiving immunosuppressive therapy tend to have lower serum itraconazole levels on standard doses and are thus at high risk of therapeutic failure.

Method Description

Itraconazole and hydroxyitraconazole are extracted by mixing serum samples with acetonitrile to precipitate proteins. The supernatant is removed and analyzed by an in-house developed liquid chromatography-tandem mass spectrometry method.(Unpublished Mayo method)

Report Available

1 to 3 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Forms

If not ordering electronically, complete, print, and send a Therapeutics Test Request (T831) with the specimen.