Seroquel (quetiapine): Antipsychotic Side Effects & Dosage

What is quetiapine (Seroquel)? What is quietiapine used for?

Quetiapine is an oral atypical antipsychotic drug.

What brand names are available for quetiapine?

Seroquel and Seroquel XR are the brand names available for quetiapine in the US.

Is quetiapine (Seroquel, Seroquel XR) available as a generic drug?

Yes

Do I need a prescription for quetiapine (Seroquel, Seroquel XR)?

Yes

Why is quetiapine prescribed to patients?

• Seroquel or Seroquel XR is used alone or in combination with other drugs to treat schizophrenia and bipolar disorder. It also is used for treating major depression in combination with antidepressants.

What are the side effects of quetiapine?

Warning for people with high or low blood pressure and Seroquel or Seroquel XR

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 day period of treatment, when it is restarted after temporary discontinuation, and after an increase in the dose. The risk of orthostatic hypotension is about 1 in 100 (one of every hundred patients who take quetiapine).

As with other antipsychotics, long-term use of quetiapine may lead to irreversible tardive dyskinesia, a neurologic disease which consists of involuntary movements of the jaw, lips, and tongue.

Warning for people with cataracts taking Seroquel or Seroquel XR

In animals, quetiapine has been associated with the development of cataracts, and cataracts have been reported in patients using quetiapine for prolonged periods. Although it is not clear if quetiapine was responsible for the cataracts seen in humans, eye examinations by slit-lamp (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 taking Seroquel or Seroquel XR

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

Warning for people with diabetes taking quetiapine taking Seroquel or Seroquel XR

There is an increased risk of hyperglycemia (high blood glucose) and diabetes-related events in patients taking atypical antipsychotics, including quetiapine. Patients should be tested during treatment for elevated blood-sugars. Additionally, persons with risk factors for diabetes, including obesity or a family history of diabetes, should have their fasting levels of blood sugar tested before starting treatment and periodically throughout treatment to detect the onset of diabetes. Any patient developing symptoms that suggest diabetes during treatment should be tested for diabetes.

Common side effects

• The most common side effects of Seroquel or Seroquel XR are
  • headache,
  • agitation,
  • dizziness,
  • drowsiness,
  • weight gain, and
  • 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. Because of this tiredness, care should be exercised in any activity requiring mental alertness such as operating a motor vehicle or hazardous machinery.
• Less common side effects include seizures (1 in 125 patients) and hypothyroidism (1 in 250 patients).

Schizophrenia is the most disabling mental illness.
See Answer

What is the dosage for quetiapine?

• Immediate release quetiapine usually is taken two or three times daily.
• Extended release quetiapine is taken once daily.
• The dose usually is increased slowly over several days or weeks to achieve the desired effect.
• Quetiapine can be taken with or without food.
• The initial dose for bipolar disorder 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/d 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.
• The initial dose for schizophrenia 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.
• The dose range for treating major depression is 150-300 mg/day of extended release tablets. The starting does is 50 mg in the evening for 2 days increasing to 150 mg in the evening.

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Which drugs or supplements interact with quetiapine?

• Phenytoin (Dilantin) and thioridazine (Mellaril) markedly decrease the amount of Seroquel and Seroquel XR that is absorbed from the intestine and thereby reduces 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 therefore increase the blood pressure lowering effects of antihypertensive drugs and result in lower blood pressure.
• Seroquel and Seroquel XR can add to the sedating effects of other drugs that sedate. Such drugs include narcotic pain relievers (for example, oxycodone and acetaminophen [Percocet, Roxicet, Tylox, Endocet]), barbiturates, sedatives such as alprazolam [Xanax] and clonazepam [Klonopin], ethanol, and blood pressure drugs that can cause orthostatic hypotension, such as prazosin (Minipress) and terazosin (Hytrin).
• Seroquel and Seroquel XR is eliminated from the body by an enzyme in the liver called cytochrome P450 3A. There is a concern that drugs that strongly interfere with the enzyme may cause elevated and toxic levels of quetiapine, for example:
  • ketoconazole (Nizoral),
  • itraconazole (Sporanox),
  • fluconazole (Diflucan),
  • erythromycin,
  • clarithromycin (Biaxin),
  • nefazodone (Serzone),
  • verapamil (Calan, Isoptin, Verelan),
  • diltiazem (Cardizem, Tiazac, Dilacor)
  • St. John's Wort,
  • carbamazepine (Tegretol), and
  • rifampin (Rifadin).

Is quetiapine safe to use during pregnancy or while breastfeeding?

• There are no adequate studies of Seroquel and Seroquel XR in pregnant women. Studies in animals are inconsistent. Some studies suggest effects on the fetus and others show no effects. Seroquel and Seroquel XR should be used in pregnancy only if the physician feels that it is necessary and that the potential benefits justify the unknown risks.
• Seroquel and Seroquel XR is excreted in the milk of animals during lactation. Although it is not known if it is excreted in human milk, it is recommended that women taking Seroquel and Seroquel XR not breastfeed.

What else should I know about quetiapine?

What preparations of quetiapine (Seroquel, Seroquel XR) are available?

• Tablets: 25, 50, 100, 200, 300 and 400 mg.
• Tablet (Extended Release): 50, 150, 200, 300 and 400 mg

How should I keep quetiapine (Seroquel, Seroquel XR) stored?

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

How does quetiapine (Seroquel, Seroquel XR) work?

• Although the mechanism of action of quetiapine is unknown, like other atypical anti-psychotics, it inhibits communication among nerves of the brain. It does this by blocking receptors on the nerves for several neurotransmitters, the chemicals that nerves use to communicate with each other. It is thought that its beneficial effect is due to blocking of the dopamine type 2 (D2) and serotonin type 2 (5-HT2) receptors.

When was quetiapine (Seroquel, Seroquel XR) approved by the FDA?

• The FDA approved quetiapine in September 1997.