Quetiapine (Seroquel)

How does it work?

Seroquel tablets and Seroquel XL prolonged-release tablets both contain the active ingredient quetiapine, which is a type of medicine known as an atypical antipsychotic. Quetiapine is also available without a brand name, ie as the generic medicine.

Quetiapine works in the brain, where it affects various neurotransmitters, in particular serotonin (5HT) and dopamine. Neurotransmitters are chemicals that are stored in nerve cells and are involved in transmitting messages between the nerve cells.

Dopamine and serotonin are neurotransmitters known to be involved in regulating mood and behaviour, amongst other things. Psychotic illness is considered to be caused by disturbances in the activity of neurotransmitters (mainly dopamine) in the brain. Schizophrenia is known to be associated with an overactivity of dopamine in the brain, and this may be associated with the delusions and hallucinations that are a feature of this disease.

Quetiapine works by blocking the receptors in the brain that dopamine acts on. This prevents the excessive activity of dopamine and helps to control schizophrenia.

Schizophrenic patients may experience 'positive symptoms' (such as hallucinations, disturbances of thought, hostility) and/or 'negative symptoms' (such as lack of emotion and social isolation). Quetiapine is effective in relieving both positive and negative symptoms of schizophrenia, whereas the conventional antipsychotics are usually less effective against the negative symptoms.

Quetiapine is also used by specialists to treat episodes of mania and depression in people with the psychiatric illness, bipolar affective disorder (manic depression).

What is it used for?

  • Schizophrenia.
  • Treatment of manic episodes in bipolar affective disorder.
  • Treatment of major episodes of depression in bipolar affective disorder.
  • As a mood stabiliser for bipolar disorder in people whose manic, mixed or depressive episodes have responded to quetiapine treatment.
  • Seroquel XL tablets are also licensed for the treatment of major depressive episodes in people with major depressive disorder. They may be used as an add-on treatment when antidepressants alone have not been effective enough.

How do I take it?

  • The dose of this medicine that is prescribed will vary from person to person. It is important to follow the instructions given by your doctor. These will be printed on the dispensing label that your pharmacist has put on the medicine. If you are unclear about anything you should ask your doctor or pharmacist for advice.
  • Seroquel tablets are standard-release tablets that are usually taken twice a day (once a day at bedtime when treating depressive episodes of bipolar disorder). These tablets can be taken with or without food.
  • Seroquel XL tablets are prolonged-release tablets designed to release quetiapine slowly and continuously over 24 hours to help provide steady blood levels of the medicine throughout the day. Seroquel XL tablets should be taken once a day without food, at least one hour before a meal. If you are taking Seroquel XL to treat a depressive episode or as a mood stabiliser for bipolar disorder, your daily tablet should be taken at bedtime. Seroquel XL tablets should be swallowed whole and not broken, crushed or chewed, as this would damage the prolonged-release action.
  • If you forget to take a dose take it as soon as you remember. If it is nearly time for your next dose leave it until then to take it. Don't take a double dose to make up for a missed dose.
  • Unless your doctor tells you otherwise, you should not suddenly stop taking this medicine, even if you feel better and think you don't need it any more. This is because the medicine controls the symptoms of the illness but doesn't actually cure it. This means that if you suddenly stop treatment your symptoms could come back. Stopping the medicine suddenly may also rarely cause withdrawal symptoms such as nausea, vomiting, difficulty sleeping, headache, diarrhoea, dizziness and irritability. When treatment with this medicine is stopped, it should usually be done gradually over at least one or two weeks, following the instructions given by your doctor.
  • You should avoid drinking grapefruit juice or eating grapefruit while taking quetiapine, as it may increase the level of this medicine in your blood and hence increase the risk of side effects.


  • This medicine may make you feel sleepy, particularly when you first start treatment. This generally gets better after the first couple of weeks. If affected you should not drive or operate machinery.
  • This medicine can occasionally cause your blood pressure to drop when you move from a lying down or sitting position to sitting or standing, especially when you first start taking the medicine. This may make you feel dizzy or unsteady and could make you faint. To avoid this try getting up slowly. If you do feel dizzy, sit or lie down until the symptoms pass.
  • You should avoid drinking alcohol while taking this medicine, as this is likely to make any drowsiness or dizziness worse.
  • This medicine can cause some people to put on weight, usually during the early weeks of treatment. Talk to your doctor about this before you start treatment so that you can discuss strategies, such as diet and exercise, for minimising any weight gain.
  • Depression and other psychiatric illnesses are associated with an increased risk of suicidal thoughts, self-harm, and suicide. You should be aware that this medicine may not start to make you feel better for at least two to four weeks. However, it is important that you keep taking it in order for it to work properly and for you to feel better. If you feel your depression has got worse, or if you have any distressing thoughts or feelings about suicide or harming yourself in these first few weeks, or indeed at any point during treatment or after stopping treatment, then it is very important to talk to your doctor.
  • Antipsychotic medicines are associated with an increased risk of getting a blood clot in a vein (deep vein thrombosis) or in the lungs (pulmonary embolism). For this reason, you should consult a doctor immediately if you get any of the following symptoms, which could suggest you have a blood clot: stabbing pains and/or unusual redness or swelling in one leg, pain on breathing or coughing, coughing up blood or sudden breathlessness.
  • The use of quetiapine has been associated with the development of unpleasant or distressing restlessness and the need to move about, often accompanied by an inability to sit or stand still. This is most likely to occur within the first few weeks of treatment. If you experience these symptoms you should consult your doctor.
  • Consult your doctor immediately if you experience abnormal movements, particularly of the face, lips, jaw and tongue, while taking this medicine. These symptoms may be indicative of a very rare side effect known as tardive dyskinesia, and your doctor may ask you to stop taking this medicine, or decrease your dose.
  • Consult your doctor immediately if you experience the following symptoms while taking this medicine: high fever, sweating, muscle stiffness, faster breathing and drowsiness or sleepiness. These symptoms may be due to a rare side effect known as the neuroleptic malignant syndrome, and your treatment may need to be stopped.
  • You should also consult your doctor immediately if you experience any of the following side effects while taking this medicine: persistent sore throat or mouth ulcers, fever, or other signs of infections (this may indicate a problem with your blood cells); fits or seizures; allergic reactions such as a blistering skin rash, or swelling of the face, lips, throat or tongue; yellowing of the skin and whites of the eyes (jaundice); or a long-lasting and painful erection (priapism). These side effects are rare, but may be serious and may require urgent medical attention.

Use with caution in

  • Elderly people.
  • Young adults under 25 years of age with depressive episodes of bipolar disorder.
  • People with a history of suicidal behaviour or thoughts.
  • People with decreased liver function.
  • People who are dehydrated.
  • Low blood pressure (hypotension).
  • People with disease involving the heart and blood vessels (cardiovascular disease) for example heart failure, angina, previous heart attack or an irregular heartbeat (arrhythmia).
  • People with a personal or family history of an abnormal heart rhythm seen on a heart monitoring trace (ECG) as a 'prolonged QT interval'.
  • People taking medicines that can cause a 'prolonged QT interval' (see end of page for examples).
  • People with disease of the blood vessels in and around the brain (cerebrovascular disease).
  • People with risk factors for having a stroke, for example a history of stroke or mini-stroke (TIA), smoking, diabetes, high blood pressure, or a type of irregular heartbeat called atrial fibrillation.
  • People with a personal or family history of blood clots (venous thromboembolism), for example in a vein of the leg (deep vein thrombosis) or in the lungs (pulmonary embolism).
  • People with other risk factors for getting a blood clot, for example smoking, being overweight, taking the contraceptive pill, being over 40, recent major surgery or being immobile for prolonged periods.
  • People with low levels of magnesium or potassium in their blood.
  • People with low numbers of white blood cells in their blood (leucopenia), or a history of a drop in white blood cells (leucopenia) caused by a medicine.
  • People with diabetes or who are at risk of developing diabetes. (If you have diabetes your blood sugar levels should be monitored closely while you are having treatment with this medicine, because it may increase your blood sugar.)
  • People with a history of seizures, eg epilepsy.
  • Parkinson's disease.

Not to be used in

  • Breastfeeding.
  • Seroquel and Seroquel XL tablets contain lactose and are not suitable for people with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency, or glucose-galactose malabsorption.
  • Seroquel and Seroquel XL tablets are not licensed or recommended for treating behavioural problems or psychosis in elderly people with dementia, as antipsychotic medicines such as this one have been shown to increase the risk of stroke in this group of people.
  • Seroquel and Seroquel XL tablets are not recommended for children and adolescents under 18 years of age, as the manufacturer has not studied the medicine in this age group. However, quetiapine may sometimes be prescribed by specialists to treat schizophrenia or manic epsiodes of bipolar disorder in children aged 12 to 18 years. This is an unlicensed use of the medicine. If you are concerned about your child taking this medicine you should talk to their specialist.

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine for use during pregnancy has not been established. It should therefore be used with caution during pregnancy, and only if the benefits to the mother outweigh any potential risks to the developing baby. If the medicine is used during the third trimester it could cause side effects or withdrawal symptoms in the baby after birth and the baby may need extra monitoring because of this. Seek further medical advice from your doctor.
  • If you do get pregnant or want to plan a pregnancy while taking this medicine it is important to consult your doctor straight away for advice. You should not suddenly stop taking this medicine unless your doctor tells you to, as this could cause your symptoms to come back.
  • This medicine may pass into breast milk. The manufacturer recommends that mothers who need to take this medicine should not breastfeed their infants. Seek medical advice from your doctor.

Label warnings

  • This medication may cause drowsiness. If affected do not drive or operate machinery. Avoid alcoholic drink.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

  • Sleepiness.
  • Dizziness.
  • Headache.
  • Dry mouth.
  • Weight gain (see warning section above).
  • Raised levels of fats called cholesterol or triglycerides in the blood.

Common (affect between 1 in 10 and 1 in 100 people)

  • Weakness or loss of strength (asthenia).
  • Stomach upsets such as constipation, vomiting or indigestion.
  • Increased appetite.
  • Abnormal dreams and nightmares.
  • Faster than normal heartbeat (tachycardia) or awareness of your heartbeat (palpitations).
  • A drop in blood pressure that occurs when moving from a lying down or sitting position to sitting or standing, which may cause dizziness or fainting (postural hypotension – see warning section above).
  • Swelling of the legs and ankles due to excess fluid retention (peripheral oedema).
  • Shortness of breath.
  • Blurred vision.
  • Abnormal or uncontrolled movements of the hands, legs, face, eyes, neck or tongue, for example tremor, twitching or stiffness (extrapyramidal effects).
  • Problems with speech.
  • Irritability.
  • Fever.
  • Alteration in results of liver function tests.
  • Increased level of the hormone prolactin in the blood (hyperprolactinaemia) - on rare occasions this may lead to symptoms such as breast enlargement, production of breast milk and menstrual disturbances.
  • Increased blood glucose levels. Tell your doctor if you notice you feel unusually hungry or thirsty, or need to pass urine more often than usual. People with diabetes should monitor their blood sugar closely.

Uncommon (affect between 1 in 100 and 1 in 1000 people)

  • Difficulty swallowing.
  • Inflammation of the lining of the nose (rhinitis) causing a blocked or runny nose.
  • Decrease in the number of white blood cells or platelets in the blood (neutropenia or thrombocytopenia). You should consult your doctor if you experience any of the following symptoms: unexplained bruising or bleeding, purple spots, sore throat, mouth ulcers, high temperature (fever), feeling tired or general illness. Your doctor may want to take a blood test to check your blood cells.
  • Seizures.
  • Sexual problems.
  • Restless legs syndrome.
  • Tardive dyskinesia (see warning section above).
  • Abnormal heart rhythm seen as a 'prolonged QT interval' on a heart monitoring trace or ECG.

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Yellowing of the skin and whites of the eyes (jaundice).
  • Inflammation of the liver (hepatitis).
  • Neuroleptic malignant syndrome (see warning section above).
  • Abnormal blood clot in the blood vessels (venous thromboembolism - see warning section above).
  • Sleepwalking.
  • Prolonged erection (priapism). If you get an erection that lasts longer than four hours while taking this medicine, you should consult a doctor immediately. Treatment of this condition should not be delayed more than six hours, as this can cause damage to the erectile tissue in the penis and irreversible erectile dysfunction.

Very rare (affect less than 1 in 10,000 people)

  • Diabetes.
  • Severe allergic blistering skin reaction (Stevens-Johnson syndrome).
  • Allergic reaction involving swelling of the face, throat, lips or tongue (angioedema).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

The following medicines may decrease the breakdown of quetiapine by the liver and so could increase the risk of its side effects. They should not be used in combination with quetiapine:

  • azole antifungal medicines such as itraconazole, ketoconazole, fluconazole
  • macrolide antibiotics such as erythromycin, clarithromycin
  • protease inhibitors for HIV infection such as ritonavir.

There may be an increased risk of drowsiness and sedation if quetiapine is taken with any of the following (which can also cause drowsiness):

  • alcohol
  • barbiturates, eg amobarbital, phenobarbital
  • benzodiazepines, eg diazepam, temazepam
  • MAOI antidepressants, eg phenelzine
  • sedating antihistamines, eg chlorphenamine, hydroxyzine
  • sleeping tablets, eg zopiclone
  • strong opioid painkillers, eg morphine, codeine
  • tricyclic antidepressants, eg amitriptyline.

Quetiapine may enhance the blood pressure-lowering effects of medicines that lower blood pressure, including medicines used to treat high blood pressure (antihypertensives) and medicines that lower blood pressure as a side effect, eg benzodiazepines. If you are taking medicines that lower blood pressure you should tell your doctor if you feel dizzy or faint after starting treatment with this medicine, as your doses may need adjusting.

There may be an increased risk of abnormal heart rhythms (prolonged QT interval on a heart monitoring trace or ECG) if quetiapine is taken in combination with any of the following medicines:

  • antiarrhythmics (medicines to treat abnormal heart beats), eg amiodarone, procainamide, disopyramide, sotalol
  • the antihistamines astemizole, mizolastine or terfenadine
  • arsenic trioxide
  • atomoxetine
  • certain antidepressants, eg amitriptyline, imipramine, maprotiline
  • certain antimalarials, eg halofantrine, chloroquine, quinine, mefloquine, Riamet
  • certain other antipsychotics, eg thioridazine, haloperidol, sertindole, pimozide
  • cisapride
  • dronedarone
  • droperidol
  • intravenous erythromycin or pentamidine
  • methadone
  • moxifloxacin.

There may also be an increased risk of a prolonged QT interval if medicines that can alter the levels of salts such as potassium or magnesium in the blood, eg diuretics such as furosemide, are taken in combination with quetiapine.

The following medicines may increase the breakdown of quetiapine by the liver, which could make it less effective. If you are taking any of these medicines, your doctor may need to switch you onto an alternative that doesn't affect quetiapine, or prescribe you a bigger dose of quetiapine:

  • barbiturates such as amobarbital and phenobarbital
  • carbamazepine
  • phenytoin
  • rifampicin
  • thioridazine.

Quetiapine may oppose the effect of medicines for Parkinson's disease that work by stimulating dopamine receptors in the brain, for example levodopa, ropinirole, pergolide, bromocriptine.

Quetiapine may oppose the effect of anticonvulsant medicines used to treat epilepsy.

Quetiapine may increase blood sugar levels and disturb the control of diabetes. People with diabetes may need an adjustment in the dose of their antidiabetic medication.

Quetiapine may oppose the effect of histamine (used to treat leukaemia) and is not recommended for people having this treatment.

Other medicines containing the same active ingredient

  • Tenprolide XL

Quetiapine tablets are also available without a brand name, ie as the generic medicine.