Clozapine Drug Level
Label Mnemonic: CLOZ
Epic code: LAB2886
Downtime form: A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery
Commercial Mailout Laboratory
6240-8 RCP
Specimen Instructions:
Separate serum from cells as soon as possible.

Patient Prep: Timing of specimen collection: Pre-dose (trough) draw - At steady state concentration.
Collection Medium:
Red top tube 5 mL (Clot Activator)
Preferred Minimum: 1.0 mL serum
Rejection Criteria:
Whole blood. Gel separator tubes, light blue (citrate), or yellow (SPS or ACD solution).
Delivery Instructions:
Submit specimen to laboratory as soon as possible after collection.
Turn Around Time:
1-3 days upon receipt at reference laboratory
Reference Range:
Therapeutic: Not well established
Toxic: 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: Toxic ranges are not well established. Serum/plasma concentrations greater than or equal to 1500 ng/mL (clozapine, norclozapine and clozapine-N-oxide combined) may cause drug-induced agranulocytosis, Stevens-Johnson syndrome, seizures, hypotension, cardiovascular abnormalities, drowsiness, and death.

Therapeutic and toxic ranges are not well established in children.
Gel separator tubes are not recommended.
Quantitative Liquid Chromatography-Tandem Mass Spectrometry
CPT Code: