Ordering Recommendation

Optimize drug therapy and monitor patient adherence.


Quantitative Liquid Chromatography-Tandem Mass Spectrometry




1-3 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation

Timing of specimen collection: Pre-dose (trough) draw - At steady state concentration.


Plain red. Also acceptable: Lavender (K2 or K3EDTA) or pink (K2EDTA).

Specimen Preparation

Separate serum or plasma from cells within 2 hours of collection. Transfer 1 mL serum or plasma to an ARUP Standard Transport Tube. (Min: 0.5 mL)

Storage/Transport Temperature


Unacceptable Conditions

Whole blood. Gel separator tubes, light blue (citrate), or yellow (SPS or ACD solution).


After separation from cells: Ambient: 5 weeks; Refrigerated: 2 months; Frozen: 2 months

Reference Interval
Therapeutic Range Not well established
Toxic Level Total Clozapine and Metabolites: Greater than or equal to 1500 ng/mL

Interpretive Data

Therapeutic ranges are not well established. Clozapine is metabolized to norclozapine and clozapine-N-oxide. Clozapine concentrations between 100 and 700 ng/mL may correlate more with clinical response; however, non-responsiveness may also occur within this range. For refractory schizophrenia, clozapine concentrations greater than 350 ng/mL are suggested to achieve a therapeutic response.

Toxicity: Adverse effects to clozapine therapy may include tachycardia, drowsiness, hypotension, and seizures.

Therapeutic and toxic ranges are not well established in children.

Compliance Statement B: For laboratory developed tests not using a RUO kit, and for FDA approved, cleared or 510(k) exempt assays with alterations. This test was developed and its performance characteristics determined by ARUP Laboratories. The U. S. Food and Drug Administration has not approved or cleared this test; however, FDA clearance or approval is not currently required for clinical use. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions.

Hotline History
CPT Codes


Component Test Code* Component Chart Name LOINC
2013458 Clozapine, S/P, Quant 6896-5
2013459 Norclozapine, S/P, Quant 10992-6
2013460 Clozapine-N-Oxide, S/P, Quant 85497-6
2013461 Total Clozapine and Metabolites
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
  • Clopine
  • Clozaril
  • Denzapine
  • FazaClo
  • Versacloz
  • Zaponex
Clozapine and Metabolites, Serum or Plasma, Quantitative