Quetiapine

1. Introduction

Quetiapine is an atypical antipsychotic medication primarily used to manage psychiatric disorders, including schizophrenia, bipolar disorder, and major depressive disorder. It works by modulating neurotransmitters such as dopamine and serotonin in the brain. Quetiapine is available in immediate-release and extended-release formulations.

2. Indications

  • Schizophrenia (acute and maintenance treatment)
  • Bipolar disorder:
    • Manic episodes (as monotherapy or adjunctive therapy)
    • Depressive episodes
    • Maintenance therapy to prevent relapses
  • Adjunctive treatment in major depressive disorder (MDD)

3. Dosage

Adults:

  • Schizophrenia:
    • Initial dose: 25 mg twice daily.
    • Titrate to 300–400 mg/day in divided doses by Day 4.
    • Maximum dose: 800 mg/day.
  • Bipolar disorder:
    • Manic episodes: Start with 50 mg twice daily, titrate to 400–800 mg/day.
    • Depressive episodes: Start with 50 mg once daily at bedtime, increase to 300 mg by Day 4.
  • Adjunctive therapy for MDD:
    • Initial dose: 50 mg once daily at bedtime.
    • Increase to 150–300 mg/day based on response.

Elderly:

  • Start at 25 mg/day and titrate cautiously due to increased sensitivity to side effects.

Children (10–17 years):

  • Schizophrenia or bipolar disorder: Start at 25 mg twice daily, increase gradually to 400–600 mg/day.

4. Administration

  • Take orally with or without food.
  • Extended-release tablets should be swallowed whole; do not crush, chew, or break.
  • Immediate-release tablets can be taken in divided doses throughout the day.

5. Forms Available

  • Immediate-release tablets: 25 mg, 50 mg, 100 mg, 200 mg, 300 mg, 400 mg
  • Extended-release tablets: 50 mg, 150 mg, 200 mg, 300 mg, 400 mg

6. Side Effects

6.1 Common Side Effects:

  • Drowsiness
  • Dizziness
  • Dry mouth
  • Constipation
  • Weight gain

6.2 Less Common Side Effects:

  • Orthostatic hypotension
  • Increased appetite
  • Blurred vision
  • Increased cholesterol or triglyceride levels

6.3 Rare but Serious Side Effects:

  • Extrapyramidal symptoms (e.g., tremors, rigidity)
  • Neuroleptic malignant syndrome (NMS)
  • Tardive dyskinesia (involuntary movements)
  • Severe allergic reactions (e.g., angioedema)
  • Suicidal thoughts (especially in younger patients)

7. Warnings

  • Suicidal Ideation: Antidepressants may increase the risk of suicidal thoughts and behaviours in children, adolescents, and young adults.
  • Metabolic Effects: Monitor for weight gain, hyperglycaemia, and dyslipidaemia.
  • QT Prolongation: Use cautiously in patients with cardiovascular conditions or on medications that prolong the QT interval.
  • Orthostatic Hypotension: May cause dizziness or fainting, particularly during dose titration.

8. Precautions

  • Use cautiously in patients with a history of seizures, as quetiapine may lower the seizure threshold.
  • Avoid use in elderly patients with dementia-related psychosis due to an increased risk of mortality.
  • Monitor for signs of cataracts during long-term use.
  • Avoid abrupt discontinuation to prevent withdrawal symptoms like insomnia, nausea, or agitation.

9. Interactions

  • CYP3A4 inhibitors (e.g., ketoconazole): May increase quetiapine levels; reduce dose if used together.
  • CYP3A4 inducers (e.g., carbamazepine): May decrease quetiapine levels; dose adjustment may be needed.
  • CNS depressants (e.g., benzodiazepines, opioids): Additive sedative effects.
  • Antihypertensives: May enhance hypotensive effects.

10. Monitoring Parameters

  • Monitor weight, blood pressure, fasting glucose, and lipid levels periodically.
  • Assess for mood changes, suicidal thoughts, or unusual behaviour, especially during the initial weeks of treatment.
  • Monitor for extrapyramidal symptoms and tardive dyskinesia.
  • Perform regular eye examinations to monitor for cataracts.

11. Use in Children

  • Approved for use in children aged 10 years and older for schizophrenia and bipolar disorder.
  • Monitor for increased appetite, weight gain, and mood changes.

12. Use in Pregnancy

  • Category C: Use only if the benefits outweigh the potential risks.
  • Neonates exposed during the third trimester may experience withdrawal symptoms or respiratory distress.

13. Use in Elderly

  • Avoid use in elderly patients with dementia-related psychosis due to an increased risk of stroke and mortality.
  • Use cautiously, starting at the lowest dose, and monitor for sedation, orthostatic hypotension, and metabolic changes.

14. Use in Kidney Disease

  • No dose adjustment is required for renal impairment.

15. Use in Liver Disease

  • Reduce the starting dose to 25 mg/day in patients with hepatic impairment. Titrate slowly based on response.

16. Patient Counselling Points

  • Take quetiapine exactly as prescribed, at the same time(s) each day.
  • Avoid activities requiring alertness (e.g., driving) until you know how the medication affects you, as drowsiness is common.
  • Do not stop taking quetiapine suddenly; consult your doctor for a tapering schedule.
  • Report symptoms such as severe dizziness, fainting, muscle stiffness, or uncontrollable movements to your doctor immediately.
  • Monitor your weight and follow a healthy diet and exercise plan to minimise weight gain.

17. Table of Brand Names, Manufacturer, and Prices in USD

Brand NameManufacturerStrength/Dosage FormPrice (USD)
SeroquelAstraZeneca25 mg Immediate-Release Tablet$120 (30 tablets)
Seroquel XRAstraZeneca300 mg Extended-Release Tablet$300 (30 tablets)
Generic QuetiapineVarious100 mg Immediate-Release Tablet$30 (30 tablets)

18. 15 FAQs (Frequently Asked Questions)

1. What is Quetiapine used for?
Quetiapine is used to treat schizophrenia, bipolar disorder, and major depressive disorder as adjunctive therapy.

2. How does Quetiapine work?
It modulates dopamine and serotonin receptors in the brain to reduce psychotic symptoms and stabilise mood.

3. Is Quetiapine addictive?
No, quetiapine is not considered addictive, but it can cause withdrawal symptoms if stopped abruptly.

4. Can Quetiapine cause weight gain?
Yes, weight gain is a common side effect, particularly during long-term use.

5. How long does Quetiapine take to work?
It may take 2–4 weeks to notice improvements in symptoms.

6. Can Quetiapine be used in children?
Yes, it is approved for use in children aged 10 years and older for schizophrenia and bipolar disorder.

7. Can Quetiapine cause drowsiness?
Yes, drowsiness is one of the most common side effects.

8. Can I drink alcohol while taking Quetiapine?
No, alcohol can enhance the sedative effects of quetiapine and should be avoided.

9. Is Quetiapine safe during pregnancy?
It should only be used if the benefits outweigh the risks. Consult your doctor.

10. Can Quetiapine cause suicidal thoughts?
Yes, it may increase the risk of suicidal thoughts, particularly in younger patients.

11. Can Quetiapine be stopped abruptly?
No, abrupt discontinuation may cause withdrawal symptoms; taper off under medical supervision.

12. Does Quetiapine interact with other medications?
Yes, it interacts with CYP3A4 inhibitors/inducers, CNS depressants, and antihypertensives.

13. Can Quetiapine cause tremors?
Yes, it can cause tremors or other extrapyramidal symptoms in some patients.

14. How should Quetiapine be stored?
Store at room temperature, away from moisture and heat.

15. Is Quetiapine a first-line treatment for schizophrenia?
Yes, quetiapine is a commonly prescribed atypical antipsychotic for schizophrenia.