Pathology Handbook



Seroquel, Seroquel XL

Clinical Indications

Quetiapine is a dibenzothiazepine derivative used as an antipsychotic drug in schizophrenia and bipolar disorder. It acts on the chemical neurotransmitters in the brain. The assay can be useful in:

1) Assesing compliance

2) Dose adjustments

3) Investigation of suspected acute poisoning

Drug Kinetics

It is given in incremental doses to target dose of 300-400mg per day by day 4. The effective therapeutic dosage is 200-750 mg/day. It is usually taken three times a day. The half life is 6 hours. Steady state is achieved 3 days after a change of dose. Elimination is by hepatic metabolism and biliary excretion.

Request Form 

ICE request


Monday to Friday, routine hours in referral laboratory.

Specific Criteria

Samples should be collected pre-dose.

Patient Preparation

Samples should be collected pre-dose.

Turnaround Time

5 working days from reciept of the sample.


4ml. Minimum, 2ml.


Plastic EDTA Vacutainer (lemon top)

Vacutainer lemon top

Lab Handling

DO NOT SEPARATE. Store whole blood at 4°C. Sample is sent to Llandough Hospital Toxicology Laboratory analysis. 

Causes for Rejection

Unlabelled or incorrectly labelled sample.

Taken at inappropriate time.

Request not justified.

Reference Range

200-600 µg/L