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24819 Voriconazole, Serum (VORI)

Voriconazole, Serum (VORI)
Test Code: VORISO
Synonyms/Keywords
​ Vfend (Voriconazole)
Useful For
Monitoring trough levels of voriconazole is suggested in 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, 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. ​
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​2 mL ​0.6 mL
Collection Processing Instructions
​Spin down within 2 hours of draw. Send specimen in plastic vial.  Draw specimen prior to next dose for trough level.
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​ Refrigerated (preferred) ​28 days
​Ambient 28 days
Frozen 28 days
Interference

​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.

Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Mayo Clinic Laboratories Monday through Sunday ​1 day
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
Test 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.

Reference Range Information
Performing Location Reference Range
​Mayo Clinic Laboratories

​1.0-5.5 mcg/mL

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

Interpretation
Trough levels >6 mcg/mL (and especially >10 mcg/mL) have been associated with toxicity in several reports.
 
Trough levels <1 mcg/mL have been associated with suboptimal response in several reports.​
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80285
Synonyms/Keywords
​ Vfend (Voriconazole)
Ordering Applications
Ordering Application Description
​Centricity

​Voriconazole, S (88698)

​Cerner ​Voriconazole, S (88698)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
Serum​ ​Red Top Tube (RTT) ​2 mL ​0.6 mL
Collection Processing
​Spin down within 2 hours of draw. Send specimen in plastic vial.  Draw specimen prior to next dose for trough level.
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​ Refrigerated (preferred) ​28 days
​Ambient 28 days
Frozen 28 days
Interference

​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.

Useful For
Monitoring trough levels of voriconazole is suggested in 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, 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. ​
Reference Range Information
Performing Location Reference Range
​Mayo Clinic Laboratories

​1.0-5.5 mcg/mL

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

Interpretation
Trough levels >6 mcg/mL (and especially >10 mcg/mL) have been associated with toxicity in several reports.
 
Trough levels <1 mcg/mL have been associated with suboptimal response in several reports.​
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Mayo Clinic Laboratories Monday through Sunday ​1 day
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)​
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80285
For most current information refer to the Marshfield Laboratory online reference manual.