Quetiapine
Toxicology Overview / Directory
Purpose of the test
Quetiapine is a dibenzothiazepine derivative used primarily as an antipsychotic. It is generally given at an initial dose of 25 mg twice daily, with increases in increments of 25-50 mg 2 or 3 times daily on the second and third days, as tolerated, to a target dose range of 300 to 400 mg/d by day 4. Elimination of quetiapine is mainly via hepatic metabolism with a plasma half-life of about 6 h in the clinical dose range. The major metabolic pathways are sulphoxidation (to a pharmacologically inactive metabolite), N-dealkylation, and 7-hydroxylation. Effective therapeutic dosage is normally 200–750 mg/d.
Quetiapine assay can be useful in assessing adherence, in dose adjustment, and the investigation of suspected acute poisoning. A reference plasma concentration range of 50–200 µg/L has been suggested (pre-dose sample).
Sample Requirements
4 mL of ETDA whole blood is preferred. Serum or plasma can be used if required, but please avoid gel-separator tubes.
Storage and Transport
Please refrigerate (if possible) if not sending immediately. Send by first class post to:
Toxicology Unit
Top Floor, Bessemer Wing
King’s College Hospital
Denmark Hill
London SE5 9RS
Please use the form below, COMPLETE ALL FIELDS, and send as a hard copy with the sample.
PDF Request Form
Download Quetiapine Request Form
Turnaround Time
Results are available within 5 working days of receipt in the laboratory.
Price
Price available on application - please contact adrianturner1@nhs.net. Discounts could be available for significant workloads.
Contacts
Clinical Advice & Interpretation
Dr Bob Flanagan
T 020 3299 5881
F 020 3299 5888
Laboratory
Simon Handley
T 020 3299 5883
F 020 3299 5888
References
RJ Flanagan. TDM of antipsychotics. CPD Bull Clin Biochem (2006); 7: 3-18.
