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HelpTest Code VORI Voriconazole, Serum
Reporting Name
Voriconazole, SUseful For
Monitoring trough levels of voriconazole is suggested for:
-Individuals with reduced liver function
-Individuals with cytochrome P450 (CYP) 2C19 alterations associated with poor metabolic function
-Patients taking other medications that affect CYP2C19 activity
-Patients experiencing potential toxicity
Monitoring trough levels may be reasonable in patients who are not responding optimally or have drug interactions that may decrease voriconazole levels or to ensure adequate oral absorption
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Serum RedSpecimen Required
Collection Container/Tube: Red top (serum gel/SST not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 2 mL
Collection Instructions: Centrifuge and aliquot serum into plastic vial within 2 hours of collection.
Specimen Minimum Volume
0.6 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum Red | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
1.0-5.5 mcg/mL
Trough level (ie, immediately before next dose) monitoring is recommended.
Day(s) Performed
Monday through Sunday
CPT Code Information
80285
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| VORI | Voriconazole, S | 38370-3 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 88698 | Voriconazole, S | 38370-3 |
Clinical Information
Voriconazole (Vfend) is an antifungal agent approved for treatment of invasive aspergillosis and candidemia/candidiasis, as well as for salvage therapy for infections in patients refractory to, or intolerant of, other antifungal therapy. The drug inhibits the fungal enzyme 14a-sterol demethylase, a critical step in ergosterol biosynthesis.
Voriconazole is metabolized in the liver primarily by cytochrome P450 (CYP) 2C19 with CYP2C9 and CYP3A4 having limited roles. The primary metabolite is voriconazole N-oxide, which has no antifungal activity. Drug clearance is primarily dependent on hepatic metabolism. The pharmacokinetics of voriconazole is highly variable and nonlinear, which results in an increased dose leading to a greater than proportional increase in serum concentration.
The bioavailability of oral voriconazole is greater than 95%. Approximately 60% of the drug in serum is protein bound. Voriconazole has a volume of distribution of 4.6 L/kg. Most (80%) of the drug is excreted in the urine, exclusively as metabolites.
Adverse effects of voriconazole include visual disturbances, skin rashes, and elevated liver enzyme levels.
Interpretation
Trough levels above 6 mcg/mL (and especially >10 mcg/mL) have been associated with toxicity in several reports.
Trough levels below 1 mcg/mL have been associated with suboptimal response in several reports.
Cautions
Voriconazole metabolism may be altered by coadministration of drugs that metabolically induce or inhibit cytochrome P450 2C19 or by genetic alterations that affect enzyme activity.
Method Description
The serum sample is diluted in an acetonitrile internal standard. The protein precipitate is centrifuged and a portion of the supernatant is diluted with mobile phase 1 for detection by a tandem mass spectrometer.(Unpublished Mayo method)