Seroquel: 7 things you should know
Medically reviewed by C. Fookes, BPharm. Last updated on Oct 3, 2019.
1. How it works
- Seroquel is a brand (trade) name for quetiapine.
- Quetiapine acts on numerous receptors in the brain to calm and help diminish psychotic thoughts. The exact way it works is unknown; however, some experts believe its mood calming effects may be through an antagonism of dopamine and serotonin receptors. Quetiapine may also affect histamine receptors (responsible for its side effect of sedation) and adrenergic alpha1 receptors (responsible for the fall in blood pressure when standing).
- Seroquel belongs to the class of medicines known as atypical antipsychotics.
- Seroquel may be used in the treatment of schizophrenia in adults and children over the age of 13 years.
- Seroquel may also be used to treat bipolar disorder in adults and children over the age of 10.
- Its ability to also calm and make people sleepy means it may be used in addition to antidepressants or to treat other conditions (off-label uses include anxiety disorder).
- Seroquel is available as a generic under the name of quetiapine.
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Confusion, headache, drowsiness, agitation, constipation, weight gain, dry mouth and blurred vision.
- Sedation - which may affect your ability to drive or operate machinery. Avoid alcohol.
- May cause a lowering of blood pressure - this may be particularly noticeable when going from a sitting to standing position and may increase the risk of falls. Seroquel may also increase blood pressure in some people.
- Should not be used in seniors with dementia-related psychosis because it increases their risk of death.
- Interaction or overdosage may cause serotonin syndrome (symptoms include mental status changes [such as agitation, hallucinations, coma, delirium], fast heart rate, dizziness, flushing, muscle tremor or rigidity and stomach symptoms [including nausea, vomiting, diarrhea]). Another serious syndrome called Neuroleptic Malignant Syndrome (NMS) has also been reported; symptoms include high body temperature, muscle rigidity, and mental disturbances; discontinue Seroquel immediately and seek urgent medical advice if symptoms of NMS develop.
- May increase the risk of bleeding, especially if used with other drugs that also increase bleeding risk.
- May also cause anxiety, nervousness or insomnia. There is a risk of tardive dyskinesia (uncontrollable, repetitive, facial movements) associated with all antipsychotics, including Seroquel.
- Significant weight loss has been reported, although may cause weight gain in some people.
- May precipitate a manic episode in people with undiagnosed bipolar disorder.
- May cause lowering of total body sodium (hyponatremia); elderly people or people taking diuretics or already dehydrated may be more at risk.
- May cause a discontinuation syndrome if abruptly stopped; symptoms include irritability, low mood, dizziness, electric shock sensations, headache and confusion.
- High blood sugar levels that may lead to the development of diabetes and elevations in cholesterol or triglyceride levels have been reported. Hypothyroidism (low thyroid levels) associated with Seroquel use may also occur.
- As with similar medications, Seroquel may increase the risk of suicidal thoughts or behavior in young adults; risk is higher in those aged less than 25.
- The extended-release form of Seroquel should not be given to anyone younger than 18 years.
Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.
- Immediate-release tablets can be administered either with or without food. Administer extended release tablets in the evening either without food or following a light meal. Swallow extended-release tablets whole, do not crush or chew.
- Initially, lower dosages are administered. These are gradually increased as needed so that tolerance develops to side effects such as drowsiness or low blood pressure.
- Get up slowly when going from a lying or sitting position to standing.
- Seroquel may be given once a day or given multiple times a day depending on your doctor's instructions and the type of tablet given (for example, immediate vs extended release).
- Do not drive or operate machinery or perform hazardous tasks if Seroquel makes you sleepy.
- Talk to your doctor if you feel that your mood is worsening or you feel agitated or are having suicide-related thoughts.
- Avoid alcohol while taking Seroquel and keep hydrated. Avoid over-exercising.
- Tell your doctor if you experience any abnormal facial movements.
6. Response and Effectiveness
- Peak levels of Seroquel are reached 1.5 hours after administration of immediate-release tablets or 6 hours after administration of extended-release tablets. Sedative effects happen almost immediately; however, it may take up to two to three weeks to see some improvement in other symptoms and up to six weeks for the full effects to be seen.
Medicines that interact with Seroquel may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with Seroquel. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Seroquel is metabolized through CYP3A4 hepatic enzymes. Dosage decreases (up to one-sixth of the Seroquel dose) are usually necessary when given with CYP3A4 inhibitors. Dosage increases (up to fivefold) are usually necessary when given with CYP3A4 inducers.
Common medications that may interact with Seroquel include:
- CYP3A4 inducers, such as carbamazepine, oxcarbazepine, phenytoin, rifampin, St John's Wort
- CYP3A4 inhibitors, such as clarithromycin, cyclosporine, fluconazole, ketoconazole, nefazodone, ritonavir, tamoxifen, verapamil
- dexamethasone, methylprednisone, and prednisone
- HIV medications, such as indinavir, nelfinavir, and ritonavir
- medications used to treat Parkinson's Disease, such as cabergoline and levodopa
- other antidepressants or antipsychotics
Avoid drinking alcohol or taking illegal or recreational drugs while taking Seroquel.
Note that this list is not all-inclusive and includes only common medications that may interact with Seroquel. You should refer to the prescribing information for Seroquel for a complete list of interactions.
Seroquel (quetiapine fumarate) [Package Insert]. Revised 08/2019. AstraZeneca Pharmaceuticals LP. https://www.drugs.com/pro/seroquel.html
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Seroquel only for the indication prescribed.
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