Sign in →

Test Code SOFT: Z1000 Posaconazole, Serum

Additional Codes

Ordering MnemonicMayo Test ID
HOM: MISC LABPOSA

Reporting Name

Posaconazole, S

Useful For

Monitoring posaconazole therapy

Method Name

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

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: 2 mL

Collection Instructions: Within 2 hours of collection, centrifuge, and aliquot serum into plastic vial.


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

>700 ng/mL (trough)

Day(s) Performed

Monday through Saturday

CPT Code Information

80187

LOINC Code Information

Test ID Test Order Name Order LOINC Value
POSA Posaconazole, S 53731-6

 

Result ID Test Result Name Result LOINC Value
89591 Posaconazole, S 53731-6

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.

Clinical 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.(1,2)

 

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).(1,3) 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.(4,5) The drug has a high volume of distribution (Vd=465-1774 L) and is highly protein bound (≥97%), predominantly to albumin.(1,3) The drug does not undergo significant metabolism; approximately 15% to 17% undergoes non-CYP-mediated metabolism, primarily via hepatic glucuronidation into metabolites.(1) 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

Interpretation

Levels greater than 700 ng/mL (0.7 mcg/mL) have been suggested for prophylaxis.

 

Levels 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.

 

A toxic range has not been established.

Clinical Reference

1. Noxafil (posaconazole). Package insert: Schering Corporation; 2006

2. Goodman and Gilman's: The Pharmacological Basis of Therapeutics. 10th ed. McGraw-Hill Professional; 2001

3. Physicians' Desk Reference (PDR). 61st ed. Thomson PDR; 2007

4. Courtney R, Wexler D, Radwanski E, Lim J, Laughlin M. Effect of food on the relative bioavailability of two oral formulations of posaconazole in healthy adults. Br J Clin Pharmacol. 2004;57(2):218-222. doi:10.1046/j.1365-2125.2003.01977.x

5. Courtney R, Radwanski E, Lim J, Laughlin M. Pharmacokinetics of posaconazole coadministered with antacid in fasting or nonfasting healthy men. Antimicrob Agents Chemother. 2004;48(3):804-808. doi:10.1128/AAC.48.3.804-808.2004

6. Milone MC, Shaw LM: Therapeutic drugs and their management. In: Rifai N, Chiu RWK, Young I, Burnham CAD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:420-453

Method Description

Posaconazole is extracted by mixing serum samples with acetonitrile to precipitate proteins. The supernatant is removed and analyzed by a liquid chromatography tandem mass spectrometry method.(Unpublished Mayo method)

Report Available

2 to 5 days

Specimen Retention Time

2 weeks

Cautions

No significant cautionary statements

Forms

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

Secondary ID

89591