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25003 Posaconazole, Serum (POSA)

Posaconazole, Serum (POSA)
Test Code: POSACSO
Synonyms/Keywords
​​Noxafil (Posaconazole), Posaconazole (Noxafil)
Useful For
Monitoring of posaconazole therapy
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​
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​ Refrigerated (preferred)​ 28 days
Ambient ​28 days
​Frozen ​28 days
Rejection Criteria
Serum gel tube​
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Clinic Laboratories​​
Monday through Saturday
2- 5 days​
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reference Lab
Test Information

Posaconazole interferes with fungal cytochrome P450 (CYP) lanosterol-14 alpha demethylase activity, thereby decreasing synthesis of ergosterol, the principal sterol in fungal cell membrane, and inhibiting fungal cell membrane formation.

Posaconazole has been approved for prophylaxis of invasive Aspergillus and Candida infections in severely immunocompromised patients (eg, hematopoietic stem cell transplant recipients with graft-versus-host disease [GVHD] or those with prolonged neutropenia secondary to chemotherapy for hematologic malignancies) and treatment of oropharyngeal candidiasis (including patients refractory to itraconazole or fluconazole). It also is approved for ocular administration (drug monitoring not required for this use).​

Posaconazole has a variable absorption. Food and liquid nutritional supplements increase absorption, and fasting states do not provide sufficient absorption to ensure adequate plasma concentrations. The drug has a high volume of distribution (Vd=465-1774 L) and is highly protein bound (> or =97%), predominantly to albumin. The drug does not undergo significant metabolism; approximately 15% to 17% undergoes non-CYP-mediated metabolism, primarily via hepatic glucuronidation into metabolites. The half-life elimination is approximately 35 hours (range: 20-66 hours); steady state is achieved after about 5 to 7 days. Time to maximum concentration is approximately 3 to 5 hours, but due to the highly variable absorption, trough level monitoring is recommended.​

Therapeutic drug monitoring should be considered in the following situations:

-To document optimal absorption when used for prophylaxis or active treatment of a fungal infection

-Consider rechecking a level even if initial level was in the goal range, if the patient:

-Is unable to meet optimal nutritional intake

-Is receiving continuous tube feeding

-Is receiving a proton pump inhibitor (decreased posaconazole levels in some studies)

-Has mucositis, diarrhea, vomiting, GVHD, or other reason that the drug may not be absorbed well

Reference Range Information
Performing Location Reference Range
Mayo Clinic Laboratories​​
>700 ng/mL (trough)
Interpretation
Greater than 700 ng/mL (>0.7 mcg/mL) has been suggested for prophylaxis
Greater than or equal to 1250 ng/mL (1.25 mcg/mL) were shown to be optimal in a salvage trial for treatment of invasive Aspergillus infections
Toxic range has not been established.
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80187
Synonyms/Keywords
​​Noxafil (Posaconazole), Posaconazole (Noxafil)
Ordering Applications
Ordering Application Description
​COM Posaconazole, Serum (POSA)
​Cerner ​Posaconazole, Serum (POSA)
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​
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​ Refrigerated (preferred)​ 28 days
Ambient ​28 days
​Frozen ​28 days
Rejection Criteria
Serum gel tube​
Useful For
Monitoring of posaconazole therapy
Reference Range Information
Performing Location Reference Range
Mayo Clinic Laboratories​​
>700 ng/mL (trough)
Interpretation
Greater than 700 ng/mL (>0.7 mcg/mL) has been suggested for prophylaxis
Greater than or equal to 1250 ng/mL (1.25 mcg/mL) were shown to be optimal in a salvage trial for treatment of invasive Aspergillus infections
Toxic range has not been established.
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Clinic Laboratories​​
Monday through Saturday
2- 5 days​
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
​80187
For most current information refer to the Marshfield Laboratory online reference manual.