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Test ID: VORI Voriconazole, Serum

Reporting Name

Voriconazole, S

Useful For

Monitoring trough levels of voriconazole is suggested in individuals with reduced liver function, individuals with CYP2C19 polymorphisms associated with poor metabolic function, patients taking other medications that affect CYP2C19 activity, and in 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

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; CYP2C9 and CYP3A4 play 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.

Analytic Time

Same day/1 day

Day(s) and Time(s) Performed

Monday; 11 a.m.

Tuesday through Saturday; 12 a.m., 11 a.m.

Saturday; 4 p.m.

Sunday; 3 p.m.

Clinical Reference

1. Andes D, Pascual A, Marchetti O: Antifungal therapeutic drug monitoring: established and emerging indications. Antimicrob Agents Chemother. 2009 Jan;53(1):24-34

2. Hope WW, Billaud EM, Lestner J, Denning DW: Therapeutic drug monitoring for triazoles. Curr Opin Infect Dis. 2008 Dec;21(6):580-586

3. Donnelly JP, De Pauw BE: Voriconazole-a new therapeutic agent with an extended spectrum of antifungal activity. Clin Microbiol Infect. 2004 Mar;10:107-117

4. Physicians' Desk Reference: PDR. 70th ed. PDR Network; 2016

5. Brunton LL, Knollmann BC, Hilal-Dandan R: Goodman and Gilman's The Pharmacological Basis of Therapeutics. 13th ed. McGraw-Hill; 2017

6. Rifai N, Horwath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018

Method Name

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

Specimen Type

Serum Red


Specimen 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

Reference Values

1.0-5.5 mcg/mL

Trough level (ie, immediately before next dose) monitoring is recommended.

Test Classification

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

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
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