Quetiapine is an atypical antipsychotic used in schizophrenia and bipolar disorder, and at lower doses alongside other treatment in depression. It is markedly sedating, which is why it is sometimes prescribed for sleep, though that use carries the same longer-term metabolic considerations as any other.
The two effects most worth understanding in advance are daytime drowsiness in the first weeks, and weight and metabolic change over months.
Common side effects and early adjustment effects
- Drowsiness and sedation, most pronounced early and often easing over weeks
- Dizziness or light-headedness on standing, particularly when starting or increasing the dose
- Dry mouth and constipation
- Increased appetite and weight gain
- Headache
- Blurred vision
The dose is usually built up gradually, partly to limit the drop in blood pressure on standing. Rise slowly from bed or a chair in the early weeks, and do not drive or operate machinery until you know how it affects you.
Compared with some others in this group, quetiapine is less likely to cause movement side effects, though they remain possible.
Serious mood, behaviour or physical symptoms to take seriously
Neuroleptic malignant syndrome is rare but is a medical emergency. Get urgent help for the combination of high fever, marked muscle stiffness, confusion, sweating and a fast or irregular pulse.
Movement effects can develop at any stage: stiffness, slowed movement, tremor, or an inner restlessness that makes it hard to sit still. That last one, akathisia, is distressing and often mistaken for worsening anxiety, so name it specifically if you have it. See akathisia symptoms and antipsychotic movement side effects.
Tardive dyskinesia is a longer-term risk: involuntary repetitive movements, often of the face, lips or tongue. Report any new involuntary movement promptly, because early recognition matters. See tardive dyskinesia symptoms.
Also report urgently: fever with a sore throat or mouth ulcers, which can indicate a drop in white cells; fainting or a fast or irregular heartbeat; a rash that blisters or peels; and marked thirst with frequent urination, which can indicate raised blood sugar.
Sexual, sleep, weight and emotional side effects
Weight and metabolic change is the main long-term consideration. Weight gain can be substantial, and quetiapine can also raise blood sugar and blood lipids independently of weight. Raising this early is worthwhile, because monitoring and practical support work better before large changes accumulate. See antipsychotics and weight gain and diabetes risk.
Sleep and daytime function. Sedation is often useful at night and unwelcome during the day. Dose timing can sometimes be adjusted. See mental health medication and drowsiness.
Sexual side effects can occur and are worth raising rather than tolerating. Emotional flattening is also reported and may respond to a dose adjustment.
Interactions, alcohol, pregnancy and other risk factors
- Alcohol and other sedating medicines. These compound drowsiness considerably. Includes sleeping tablets, some antihistamines and opioid painkillers. See mental health medication and alcohol.
- Some antifungals and antibiotics. Certain ones raise quetiapine levels substantially. Mention your medicine whenever either is prescribed.
- Medicines affecting heart rhythm. Tell any prescriber what you take.
- St John’s Wort. Can reduce the effect. See St John’s Wort interactions.
- Pregnancy and breastfeeding. Needs individual discussion. Do not stop on discovering a pregnancy without advice. See mental health medication in pregnancy.
- Older adults with dementia. Antipsychotics carry particular risks in this group and are used only after careful assessment.
What to ask your doctor before changing dose or stopping
Monitoring for this group usually covers weight and waist measurement, blood glucose or HbA1c, cholesterol and other lipids, blood pressure, and periodic blood counts, with an ECG in some circumstances. These checks exist because the metabolic effects develop quietly and are far easier to address early.
Do not stop suddenly. Abrupt discontinuation can cause withdrawal effects including nausea, sweating, insomnia and agitation, and carries a real risk of the underlying condition returning. Reduction is planned with your prescriber.
- When were my weight, blood sugar and lipids last checked?
- Can the dose or timing change to reduce daytime drowsiness?
- Which movement symptoms should I report immediately?
- How long am I expected to take this, and how would we reduce it?
- Is it safe for me to drive?
Related mental health medication guides
- Antipsychotic side effects and atypical antipsychotics
- Mental health medication side effects
- Should I stop my mental health medication
- When to call a doctor
- Report a side effect in South Africa
Medical Disclaimer: This content is for informational and educational purposes only and does not constitute medical diagnosis, prescription, or professional advice. Always read the patient information leaflet and consult a qualified doctor or pharmacist regarding any medicine or health concern.