Clozapine Drug Level
Commercial Mail-out Laboratory
Separate serum from cells as soon as possible.
Patient Prep: Timing of specimen collection: Pre-dose (trough)
draw - At steady state concentration.
|Red top tube 5 mL (Clot Activator)
Preferred Minimum: 1.0 mL serum
Whole blood. Gel separator tubes, light blue (citrate), or yellow (SPS
or ACD solution).
Submit specimen to laboratory as soon as possible after collection.
1-3 days upon receipt at reference laboratory
Therapeutic: Not well established
Toxic: Greater than or equal to 1500 ng/mL
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