Quetiapine

Quetiapine is a prescription drug used for the treatment of bipolar disorder and schizophrenia. It belongs to a family of drugs known as atypical antipsychotics. Other members of this family include clozapine (Clozaril) and risperidone (Risperdal). Quetiapine is marketed as Seroquel by AstraZeneca and was approved in the US in 2004. Since it was launched in 1997, it is estimated that quetiapine has been prescribed to more than 25 million patients worldwide.

Uses

Quetiapine is specifically indicated for the treatment of depression and mania symptoms in bipolar disorder. It is also indicated for treating people with schizophrenia. The drug is approved in 88 countries for the treatment of schizophrenia, in 77 countries for the treatment of bipolar mania, and in 11 countries (including the US) for the treatment of bipolar depression. Published studies have supported its utility in treating patients with substance dependence disorder.^[1]

Other potential uses for quetiapine include the prevention of migraine headaches^[2] and in treating obsessive-compulsive disorder.^[3]

How Quetiapine is Taken

Quetiapine is available in oral tablets containing 25, 50, 100, 200, 300, or 400 mg of active ingredient.

In Depression in Bipolar Disorder

Quetiapine is administered once daily at bedtime tapered up to 300 mg daily by Day 4.

In Mania in Bipolar Disorder

Quetiapine is started at 100 mg daily on Day 1, tapered up to 400 mg daily on Day 4. Further dosage adjustments up to 800 mg daily by Day 6 are made in increments of no greater than 200 mg daily.

In Schizophrenia

Quetiapine is administered with an initial dose of 25 mg twice a day, with increases in increments of 25-50 mg twice or three times a day on the second and third day, as tolerated, to a target dose range of 300 to 400 mg daily by the fourth day, given twice or three times a day.

How Quetiapine Works

The exact mechanism of action of quetiapine is unknown. However, the effectiveness of quetiapine in schizophrenia and bipolar disorder is believed to be mediated through inhibiting dopamine type 2 (D2) and serotonin type 2 (5HT2) receptors in the brain.^[4]

How the Body Affects Quetiapine

Quetiapine is rapidly absorbed, reaching peak circulating levels in 1.5 hours.

Quetiapine is extensively metabolized by the liver. The liver enzyme CYP3A4 is involved in the metabolism of quetiapine to its major, but inactive, sulfoxide metabolite.

Less than 1% of the original dose is excreted as unchanged drug, indicating that quetiapine is highly metabolized. Approximately 73% and 20% of the original dose is excreted in the urine and feces, respectively.

Side Effects

The most common side effects (occurring >5% of treated people) likely attributable to quetiapine use are:

• Somnolence (sleepiness)
• Dizziness
• Dry mouth
• Constipation
• Liver enzyme abnormalities
• Weight gain
• Dyspepsia (indigestion)

Risks and Precautions

• Elderly patients with dementia-related psychosis treated with atypical antipsychotic drugs like quetiapine are at an increased risk of death.

Drug Interactions

The following drugs are known or likely to produce drug interactions with Seroquel:

• Drugs that act on the central nervous system including alcohol
• Blood pressure medications
• Phenytoin
• Divalproex
• Thioridazine
• Cimetidine
• CYP3A inhibitors (such as ketoconazole, itraconazole, fluconazole, erythromycin, and protease inhibitors)
• Fluoxetine, Imipramine, Haloperidol, and Risperidone

Effectiveness

One study shows quetiapine to be an effective antipsychotic for the treatment of schizophrenia.^[5]

Another studies have shown that patients with bipolar disorder who received treatment with quetiapine plus a mood stabilizer showed a 70% reduction in the risk of recurrence of a mood event (manic, mixed or depressed) compared to patients on a mood stabilizer alone.^[6]

References

1. ↑ Sattar SP, Bhatia SC, Petty F. Potential benefits of quetiapine in the treatment of substance dependence disorders. J Psychiatry Neurosci. 2004 Nov;29(6):452-7. Abstract | Full Text | PDF
2. ↑ Krymchantowski AV, Jevoux C. Quetiapine for the prevention of migraine refractory to the combination of atenolol + nortriptyline + flunarizine: an open pilot study. Arq Neuropsiquiatr. 2008 Sep;66(3B):615-8. Abstract | PDF
3. ↑ Kordon A, Wahl K, Koch N, et al. Quetiapine addition to serotonin reuptake inhibitors in patients with severe obsessive-compulsive disorder: a double-blind, randomized, placebo-controlled study. J Clin Psychopharmacol. 2008 Oct;28(5):550-4. Abstract
4. ↑ Kuroki T, Nagao N, Nakahara T. Neuropharmacology of second-generation antipsychotic drugs: a validity of the serotonin-dopamine hypothesis. Prog Brain Res. 2008;172:199-212. Abstract
5. ↑ Small JG, Hirsch SR, Arvanitis LA, Miller BG, Link CG. Quetiapine in patients with schizophrenia. A high- and low-dose double-blind comparison with placebo. Seroquel Study Group. Arch Gen Psychiatry. 1997 Jun;54(6):549-57. Abstract
6. ↑ Vieta E, Suppes T, Eggens I, Persson I, Paulsson B, Brecher M. Efficacy and safety of quetiapine in combination with lithium or divalproex for maintenance of patients with bipolar I disorder (international trial 126). J Affect Disord. 2008 Aug;109(3):251-63. Abstract

External Links

• Seroquel Web site
• MedlinePlus
• FDA: Patient Information Sheet
• Drugs.com
• Rx List