Quetiapine (Seroquel)

Primer

Quetiapine (Trade name: Seroquel) is an antipsychotic in the atypical antipsychotic class used in the treatment of schizophrenia, bipolar disorder, and major depressive disorder. It is also commonly used off-label for numerous other indications and psychiatric disorders.

Pharmacokinetics

See also article: Introduction to Pharmacology

Pharmacokinetics of Quetiapine

Absorption	Tmax = 1-3 hours
Distribution
Metabolism
Elimination
Half-life	Half-life = 6-12 hours

See also article: Cytochrome (CYP) P450 Metabolism

Quetiapine: Cytochrome P450 Metabolism

Substrate of (Metabolized by)
Induces
Inhibits

Pharmacodynamics

Mechanism of Action

See also: Mechanism of Action of Quetiapine

Quetiapine is a:
- Partial agonist
  - Serotonin 5-HT1A
- Antagonist at:
  - Serotonin 5-HT2 (a key feature of all atypical antipsychotics)
  - Dopamine D1 and D2
  - Histamine H1 (antihistaminergic effects cause sedation)
  - Adrenergic alpha 1 and alpha 2 receptors (causes hypotension)
Of all antipsychotics, quetiapine (followed by clozapine) has the lowest affinity for the D2 receptor.^[1] It dissociates the quickest from the D2 receptor, in about 15 seconds (this has been referred to the “kiss and run” hypothesis).^[2]^[3]
- As a result, these rapidly dissociating atypical antipsychotics have a very low incidence of EPS.

Toxicity

Indications

Bipolar I disorder
- 600 mg PO daily (dose range 400 to 800 mg) is an effective target dose in treating acute mania for bipolar I disorder^[4]
Bipolar II disorder
Schizophrenia
Major depressive disorder

Dosing (Immediate vs. Extended Release)

Quetiapine Immediate Release (IR) vs. Extended Release (XR)

Generic name	Quetiapine Immediate Release (IR)	Quetiapine Extended Release (XR)
Tradename	Seroquel IR	Seroquel XR
Dosage Strengths	25 mg, 50 mg, 100 mg, 150 mg, 200 mg, 300 mg, 400 mg tablets	50 mg, 150mg, 200mg, 300mg, 400mg tablets
Half-life	Shorter	Longer
Dosing	BID dosing	Once daily dosing
Starting Dose (Bipolar Mania)	50 mg BID (increase by 100-200 mg/day)	300 mg PO daily (can increase by 300 mg/day)
Target Dose (Bipolar Mania)	400-800 mg PO daily^[5]	400-800 mg PO daily
Advantages	May be more beneficial in acute mania and psychosis due to more sedating features	Faster dose titration and less sedating.^[6]
Disadvantages	More sedating	Lower side effect profile

Titration

Sedation and weight gain can be dose limiting factors in the use of quetiapine. In this case, if one were to use this approach, one should start at a low dose of 25 mg PO qHS and increase as indicated and tolerated in 25 mg increments every 2-3 weeks. Maximum dose can go up to 1200mg.
On inpatient units, if using quetiapine for psychosis or mania, rapid increases by 100 to 200mg/day is OK.^[7]

Formulations

Quetiapine comes in oral and liquid formulations

Monitoring

Contraindications

Absolute

Relative

Drug-Drug Interactions

Side Effects

Adverse Events

Neuroleptic malignant syndrome
There does not appear to be a bleeding risk, however, there are other possible haematological side effects (i.e., leucopenia and neutropenia)
- CBC should be monitored
QTc prolongation is also possible, though relatively low risk

Clinical Pearls

Special Populations

Geriatric

See main article: Geriatric Pharmacology

Pediatric

See main article: Pediatric Pharmacology

Obstetric and Fetal

See main article: Obstetric and Fetal Pharmacology

Medically Ill

See main article: Psychotropic Dosing in the Medically Ill

Resources

¹⁾ Seeman P. Atypical antipsychotics: mechanism of action. Can J Psychiatry. 2002 Feb;47(1):27-38.

²⁾ Kapur, S., & Seeman, P. (2000). Antipsychotic agents differ in how fast they come off the dopamine D2 receptors. Implications for atypical antipsychotic action. Journal of Psychiatry and Neuroscience, 25(2), 161.

³⁾ Schatzberg, AF, Nemeroff, C . The American Psychiatric Publishing Textbook of Psychopharmacology. 4th ed. American Psychiatric Publishing, 2009.

⁴⁾ Vieta, E., Goldberg, J. F., Mullen, J., Vågerö, M., & Paulsson, B. (2007). Quetiapine in the treatment of acute mania: Target dose for efficacious treatment. Journal of affective disorders, 100, S23-S31.

⁵⁾ Young, A. H., McElroy, S. L., Bauer, M., Philips, N., Chang, W., Olausson, B., ... & Brecher, M. (2010). A double-blind, placebo-controlled study of quetiapine and lithium monotherapy in adults in the acute phase of bipolar depression (EMBOLDEN I). The Journal of clinical psychiatry, 71(2), 150-162.

⁶⁾ Riesenberg, R. A., Baldytcheva, I., & Datto, C. (2012). Self-reported sedation profile of quetiapine extended-release and quetiapine immediate-release during 6-day initial dose escalation in bipolar depression: a multicenter, randomized, double-blind, phase IV study. Clinical therapeutics, 34(11), 2202-2211.

⁷⁾ Pajonk, F. G. B., Schwertner, A. K., & Seelig, M. A. (2006). Rapid dose titration of quetiapine for the treatment of acute schizophrenia and acute mania: a case series. Journal of Psychopharmacology, 20(1), 119-124.

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