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Test Code Clozapine Clozapine, Serum

Useful For

Monitoring patient compliance


An aid to achieving desired plasma levels

Method Name

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

Reporting Name

Clozapine, S
Seattle Children's Hospital Note:

Clinical System Name: Clozapine Level

Specimen Type

Serum Red

Specimen Required

Container/Tube: Red top

Specimen Volume: 1 mL

Additional Information: Therapeutic range (trough level) applies to specimens drawn immediately prior to next dose.

Specimen Minimum Volume

0.6 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Red Refrigerated (preferred) 14 days
  Ambient  14 days
  Frozen  14 days

Reject Due To


Mild OK; Gross OK


Mild OK; Gross OK


Mild OK; Gross reject


Serum gel tube

Reference Values


Therapeutic range: >350 ng/mL



Therapeutic range: >450 ng/mL

Method Description

Deuterated stable isotope of clozapine (clozapine-d4) is added to a serum sample as an internal standard. Protein is precipitated from the mixture by the addition of acetonitrile. Clozapine, norclozapine, and the internal standard are extracted from the resulting supernatant by an online extraction utilizing high-throughput liquid chromatography. This is followed by conventional liquid chromatography and analysis on a tandem mass spectrometer equipped with a heated nebulizer ion source.(Unpublished Mayo method)

Day(s) and Time(s) Performed

Monday through Friday

Seattle Children's Hospital Note:

TAT: 5 - 6 days

Performing Laboratory

Mayo Medical Laboratories in Rochester

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


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CLZ Clozapine, S 65632-2


Result ID Test Result Name Result LOINC Value
33840 Clozapine 6896-5
33841 Norclozapine 10992-6
33842 Clozapine+Norclozapine Total 12375-2