quetiapine

Quetiapine is a prescription antipsychotic drug used to treat schizophrenia and bipolar disorder. It is also used for major depression in combination with antidepressants.

Warnings

Warning for people with high or low blood pressure

• Seroquel or Seroquel XR can cause orthostatic hypotension (a drop in blood pressure upon standing that can lead to dizziness or fainting), especially during the first 3-5 days of treatment, after temporary discontinuation, or after an increase in the dose. The risk of orthostatic hypotension is about 1 in 100 (one in every hundred patients who take quetiapine).
• Long-term use of quetiapine may lead to irreversible tardive dyskinesia, a neurologic disease characterized by involuntary movements of the jaw, lips, and tongue.

Warning for people with cataracts

• Quetiapine has been associated with cataract development in animals, and cataracts have been reported in patients using quetiapine for prolonged periods. Eye examinations to identify cataracts before they impair vision are recommended at the beginning of treatment and every six months during treatment. If cataracts form, treatment should be discontinued.

Warning for people with high triglycerides or cholesterol

• Quetiapine may increase blood concentrations of cholesterol and triglycerides by 11% and 17% respectively.

Warning for people with diabetes taking quetiapine

• Patientstaking atypical antipsychotics, including quetiapine, have an increased risk of hyperglycemia (high blood glucose) and diabetes-related events. Patients should be tested for elevated blood sugars during treatment. Additionally, persons with risk factors for diabetes should have their fasting levels of blood sugar tested before starting treatment and periodically throughout treatment. Any patient developing symptoms suggesting diabetes should be tested for diabetes.

Side effects

The most common side effects of Seroquel or Seroquel XR are:

• headache,
• agitation,
• dizziness,
• drowsiness,
• weight gain, and
• stomach upset.

Possible serious side effects include:

• suicidality,
• worsening of depression,
• extrapyramidal symptoms,
• tarkive dykinesia,
• serious allergic reactions,
• seizures,
• stroke, and
• priapism.

Other important side effects include a potentially fatal complex referred to as neuroleptic malignant syndrome (NMS), in which patients may have:

• high fevers,
• muscle rigidity,
• altered mental status,
• irregular pulse or blood pressure,
• rapid heart rate,
• excessive sweating, and

heart arrhythmias.

Quetiapine frequently causes tiredness (1 in 5 patients), especially during the first 3-5 days of treatment. Care should be exercised in any activity requiring mental alertness such as operating a motor vehicle or hazardous machinery.

Dosage

• Immediate-release quetiapine is usually taken two or three times daily.
• Extended-release quetiapine is taken once daily.
• The dose is usually increased slowly over several days or weeks to achieve the desired effect.
• Quetiapine can be taken with or without food.
• Bipolar disorder: The initial dose is 50 mg twice daily (100 mg/day) of immediate-release quetiapine. The dose can be increased by 100 mg/day to a daily dose of 400 mg/day. Most patients respond to 400-800 mg/day. Doses greater than 800 mg/day have not been studied. The starting dose is 300 mg once daily and the target dose is 400-800 mg once daily when using extended-release tablets.
• Schizophrenia: The initial dose is 25 mg twice daily (50 mg/day) of immediate-release tablets. The dose can be increased by 25-50 mg two or three times daily. The target dose is 300-400 mg/day in two or three doses. Patients respond to 150-750 mg/day, and doses greater than 800 mg/day have not been evaluated. The starting dose is 300 mg once daily, and the target dose is 400-800 mg once daily when using extended-release tablets.
• Major depression: The dose range for treating major depression is 150-300 mg/day of extended-release tablets. The starting dose is 50 mg in the evening for 2 days, increasing to 150 mg in the evening.

Drug interactions

• Phenytoin (Dilantin) and thioridazine (Mellaril) decrease the absorption of Seroquel and Seroquel XR from the intestine, reducing its effectiveness. Therefore, patients taking phenytoin or thioridazine may require higher doses of Seroquel and Seroquel XR.
• Seroquel and Seroquel XR can cause hypotension (low blood pressure) and enhance the blood pressure-lowering effects of antihypertensive drugs.
• Seroquel and Seroquel XR can enhance the sedating effects of other drugs that have sedative properties.
• Drugs that strongly interfere with the liver enzyme cytochrome P450 3A may cause elevated and toxic levels of quetiapine.

Pregnancy and breastfeeding

• There are no adequate studies of Seroquel and Seroquel XR in pregnant women. Studies in animals are inconsistent. Seroquel and Seroquel XR should be used in pregnancy only if necessary and if potential benefits justify unknown risks.
• Seroquel and Seroquel XR are excreted in the milk of animals during lactation. Breastfeeding is not recommended for women taking Seroquel and Seroquel XR.

Storage

• Tablets should be stored at room temperature, 15°C to 30°C (59°F to 86°F).

Mechanism of action

• Quetiapine inhibits communication among nerves of the brain by blocking receptors for neurotransmitters, specifically dopamine type 2 (D2) and serotonin type 2 (5-HT2) receptors.

Brand names and approval

• Quetiapine tablets are available in strengths of 25, 50, 100, 200, 300, and 400 mg.
• Quetiapine extended-release tablets are available in strengths of 50, 150, 200, 300, and 400 mg.
• The FDA approved quetiapine in September 1997.

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Summary

Quetiapine is an antipsychotic drug prescribed to treat bipolar disorder and schizophrenia. Common side effects include dizziness, drowsiness, and weight gain. Possible serious side effects include seizures, stroke, priapism (prolonged erection), irregular pulse or blood pressure, rapid heart rate, and excessive sweating. Consult your doctor prior to taking this medication if pregnant or breastfeeding.