Quetiapine: uses, dosage and side effects

Quetiapine is an atypical antipsychotic taken as a tablet and prescribed for schizophrenia and for bipolar disorder, including its use as an add-on in depression that has not responded to an antidepressant alone. In Ireland it is prescription-only and it is not a controlled drug. Treatment is normally started and reviewed by a specialist or by a GP working with one. This page explains what quetiapine does, how it is taken, which side effects are reported most often and how continuing an established course works.

What quetiapine is used for

Quetiapine is licensed for schizophrenia and for bipolar disorder, where it is used in manic episodes, in bipolar depression and to prevent recurrence. Extended-release tablets are also licensed as add-on treatment in major depressive disorder when an antidepressant alone has not been enough. It acts on several receptor systems, principally dopamine and serotonin, and it also blocks histamine receptors, which explains why it is sedating. In practice prescribers use different doses for different purposes, and the dose that calms sleep is far lower than the dose used to treat psychosis, which is one reason the tablets should never be shared or reused from an old pack. Quetiapine controls symptoms rather than curing the underlying condition, so it is normally taken over long periods with regular review. Decisions about starting, changing or stopping it belong with the doctor responsible for your psychiatric care.

Side effects of quetiapine

The most frequently reported effects are drowsiness and sedation, dizziness, dry mouth, headache, constipation and weight gain, together with a drop in blood pressure when standing up, which is why the dose is increased gradually at the start. Over longer periods quetiapine can raise blood sugar, blood lipids and body weight, so most treatment plans include periodic checks of weight, glucose and cholesterol. Movement side effects such as stiffness or restlessness are less common than with older antipsychotics but still occur. Rare and serious problems include neuroleptic malignant syndrome, marked changes in heart rhythm, a fall in white blood cells and, over years, tardive dyskinesia. One warning belongs on this page because quetiapine is licensed in bipolar depression and, in its extended-release form, as add-on treatment in major depressive disorder: in the first weeks of treatment and after every dose change, anxiety, agitation and thoughts of self-harm or suicide can become worse rather than better, and this is seen most clearly in people under 25 years of age. Tell someone close to you that treatment has started or that the dose has changed, so that they can speak up if they notice it, and contact your GP the same day if it happens. Seek urgent medical help immediately for that, for high fever with muscle stiffness and confusion, for fainting or a very irregular heartbeat, or for fever with a sore throat that appears during treatment. How often each effect occurs, with its formal frequency category, is set out in the patient information leaflet. In an emergency in Ireland ring 112 or 999.

Dosage and how to take it

Quetiapine comes as immediate-release tablets, usually taken twice a day, and as extended-release tablets, usually taken once a day in the evening. Extended-release tablets are swallowed whole and taken without food or with a light meal as described in the leaflet; the two forms are not interchangeable tablet for tablet. Doses are increased in steps at the start because of dizziness and low blood pressure, and the target dose depends entirely on what is being treated. Never adjust the dose yourself, and never use a leftover pack prescribed for a different purpose. If you miss a dose, take it when you remember unless the next dose is close, in which case skip it rather than doubling up. Do not stop suddenly after regular use: abrupt withdrawal can cause nausea, insomnia and agitation and can trigger relapse, so tapering is planned with your doctor.

Is quetiapine available without a prescription in Ireland?

No. Quetiapine is prescription-only in Ireland and cannot be supplied over the counter. It is not a controlled drug, which is a separate legal category covering opioids, benzodiazepines and stimulants, but the prescription requirement here is not a formality: the medicine needs baseline assessment, dose titration and metabolic monitoring, and the correct dose depends on the diagnosis being treated. Quetiapine is sometimes sought online as a sleeping aid because it is sedating, which is a poor idea: the metabolic and cardiac effects apply regardless of why it is taken, and licensed treatments for insomnia are assessed differently. A prescription written by a doctor in another EU or EEA country can be dispensed in Ireland when it carries the details required for cross-border prescriptions, and the Pharmaceutical Society of Ireland publishes guidance for pharmacists on how to handle such prescriptions.

Why we do not assess quetiapine online

We do not assess antipsychotics online at the moment, not even as a continuation of treatment a prescriber has already established. There is nothing to buy on this page and no fee to pay. The reason is the nature of the service: you answer a written questionnaire and a doctor reviews it separately, with no video consultation, no telephone appointment and no live chat. Quetiapine also requires specialist review and blood monitoring of weight, glucose and lipids, and a written questionnaire cannot stand in for either. If you are already taking quetiapine and your supply is running low, contact your GP or the service following you in good time, and do not stop on your own, because stopping abruptly can cause withdrawal symptoms. If you are newly unwell, if your symptoms have changed, or if you are having thoughts of harming yourself, contact your GP, an out-of-hours GP service, or an emergency service on 112 or 999.

Cost and reimbursement in Ireland

Quetiapine is available from several manufacturers, so private prices are usually moderate, but they vary because each pharmacy sets its own. Holders of a medical card receive prescribed medicines under the GMS scheme for a small charge per item, subject to a monthly household cap. Everyone else can use the Drugs Payment Scheme, which caps what one household pays for prescribed medicines in a calendar month; the HSE publishes the current charge and cap, so use that figure rather than an older page. Mental health conditions are not on the Long Term Illness Scheme list, so that scheme does not usually apply. Extended-release tablets generally cost more than immediate-release ones, which occasionally prompts a switch, and a switch between the two forms is a clinical decision because the dosing is not equivalent. Raise cost with your prescriber rather than rationing tablets, because interrupted antipsychotic treatment carries a real risk of relapse.

Interactions and alcohol

Alcohol adds to the sedation quetiapine already causes and worsens the drop in blood pressure on standing, so drinking is discouraged, particularly early in treatment. Quetiapine is broken down by liver enzymes, so medicines that strongly inhibit them, including certain antifungals, some antibiotics and some antivirals, can raise its levels substantially, while carbamazepine, phenytoin and rifampicin can lower them so much that the medicine stops working. Grapefruit juice affects the same pathway. Combining quetiapine with other sedating medicines, including antihistamines and sleep medicines, increases drowsiness, and combining it with medicines that prolong the QT interval on the heart tracing requires care. Tell your pharmacist about everything you take, including anything bought over the counter and herbal products such as St John's wort. Do not drive or operate machinery until you know how the tablets affect your alertness, which can take longer than you expect after a dose increase.

Who should not take quetiapine

Quetiapine must not be taken by anyone allergic to it or to any ingredient of the tablets, or together with the liver enzyme inhibitors named as contraindications in the product information. Caution and closer monitoring apply in cardiovascular disease, in low blood pressure or a tendency to faint, in a history of seizures, in liver disease, in a personal or family history of QT prolongation or of a low white cell count, and in diabetes or a strong risk of it, because of the metabolic effects. Older people with dementia should generally not be treated with antipsychotics for behavioural symptoms, because that use is associated with increased mortality; this is one of the clearest cautions in the class. A history of a blood disorder, of thyroid disease or of urinary retention is relevant. Declare everything you take and everything in your history, because with this medicine the omitted detail is usually the important one.

Generic and brand names

The active substance is quetiapine, originally marketed as Seroquel, with the extended-release form sold as Seroquel XR; several generic versions of both are available in Ireland. Generic tablets contain the same active substance in the same strength and are approved on that basis, so the pharmacy may supply a different manufacturer from your previous pack. What must not be swapped casually is the form: immediate-release and extended-release tablets are dosed differently and switching between them is a prescribing decision, not a substitution at the counter. On a cross-border prescription, the medicine should be named by its international non-proprietary name, quetiapine, with the strength, the form, whether it is prolonged-release, and the quantity, because those details are what an Irish pharmacist needs to dispense it correctly. If your tablets look different from last time, ask the pharmacist before assuming an error.

Pregnancy and breastfeeding

Quetiapine is used in pregnancy only when the prescriber judges the benefit to outweigh the risk, and that judgement belongs to the specialist who knows your history, because relapse of a serious psychiatric illness in pregnancy is itself dangerous. Babies exposed late in pregnancy can show short-lived agitation, tremor, feeding difficulty or breathing problems after birth, so the maternity team must know that quetiapine is being taken. Blood glucose is monitored more closely because of the metabolic effects. Small amounts pass into breast milk, and decisions about breastfeeding are made individually, watching the infant for sedation. Never stop an antipsychotic abruptly because of a positive pregnancy test; contact the prescribing team first, since abrupt withdrawal can precipitate relapse. Our online questionnaire does not lead to prescriptions for use during pregnancy or breastfeeding.

Patient information leaflet

Every pack sold in Ireland contains a patient information leaflet, and the same leaflet is published online. The Health Products Regulatory Authority (HPRA) is the medicines regulator here and lists authorised products with their leaflets and summaries of product characteristics; medicines.ie publishes the same documents for products marketed in Ireland. With quetiapine, check that the leaflet you read matches both the manufacturer and the form of your pack, because immediate-release and prolonged-release tablets carry different instructions about food and about swallowing the tablet whole. Read it before starting a new pack, since the wording on warnings is updated from time to time. If anything does not match what you were told, ask your pharmacist rather than guessing; pharmacists in Ireland are registered with the Pharmaceutical Society of Ireland. A suspected side effect can be reported by you directly to the HPRA.

Who wrote and checked this page

This page was prepared by the medical content team at MEDINOW Sp. z o.o. and reviewed by lek. Damian Wojno, a doctor registered in Poland, PWZ no. 3211301. He holds no Irish registration and does not practise in Ireland; he works to Polish professional rules and issues cross-border prescriptions under Directive 2011/24/EU and Directive 2012/52/EU, which is the framework an Irish pharmacist applies when a prescription comes from another EU or EEA country. The content was verified on 29 August 2026 against the sources listed below, all of them official or regulator-published. This page is general information about a medicine: it is not personal medical advice, not a diagnosis and not an offer of the medicine itself, which we never supply. If your symptoms are new, severe or changing, contact your GP or a pharmacist; in an emergency in Ireland ring 112 or 999.

Is quetiapine prescription-only in Ireland?

Yes. It is prescription-only, though it is not a controlled drug. A prescription written by a doctor in another EU or EEA country can be dispensed in an Irish pharmacy when it carries the details required for cross-border prescriptions.

How long does it take to work?

Sedation is noticeable from the first doses, calming of agitation over days, and the fuller effect on psychotic or mood symptoms over some weeks at a stable dose. Because the dose is increased gradually, early days do not show what the target dose will do.

What are the common side effects?

Drowsiness, dizziness on standing, dry mouth, constipation and weight gain are reported most often, along with longer-term effects on blood sugar and cholesterol that are checked periodically. Fever with muscle stiffness and confusion needs urgent medical assessment.

Can I drink alcohol with it?

Alcohol is best avoided. It adds to sedation and to the fall in blood pressure on standing, increasing the risk of falls and of impaired driving, and it also makes the underlying condition harder to treat.

How do I get a repeat prescription?

Only for treatment that a specialist or GP has already established, with an unchanged dose and up-to-date monitoring. You complete our online questionnaire, a doctor reviews it separately and, if treatment can continue, you receive a cross-border prescription as a PDF by e-mail. It bridges an existing prescription and does not replace specialist care.