Seroquel (quetiapine) is an atypical antipsychotic medication indicated for the treatment of schizophrenia, bipolar disorder, and as adjunctive therapy in major depressive disorder. It functions primarily as an antagonist at multiple neurotransmitter receptors, including serotonin and dopamine receptors, which contributes to its broad efficacy profile and distinct side effect landscape. This medication is available in both immediate-release and extended-release formulations, allowing for tailored treatment approaches based on individual patient needs and clinical presentation. Proper dosing, monitoring, and patient education are paramount for achieving optimal therapeutic outcomes while minimizing potential risks.

Features

• Active Ingredient: Quetiapine fumarate
• Available Formulations: Immediate-release (Seroquel) and extended-release tablets (Seroquel XR)
• Dosage Strengths: Ranges from 25 mg to 400 mg for immediate-release; 50 mg to 400 mg for extended-release
• Mechanism of Action: Antagonist activity at serotonin (5-HT2A), dopamine (D2), histamine (H1), and adrenergic (α1 and α2) receptors
• Half-life: Approximately 6 hours for immediate-release; 7-12 hours for extended-release
• Bioavailability: Extensively metabolized hepatically via CYP3A4; bioavailability is 100% for immediate-release
• Administration: Oral, with or without food (XR formulation must be taken without a high-fat meal)

Benefits

• Effective reduction of positive and negative symptoms in schizophrenia, including hallucinations, delusions, and social withdrawal
• Provides rapid stabilization of acute manic and mixed episodes in bipolar I disorder
• Demonstrates efficacy as monotherapy for bipolar depression and as adjunctive treatment for major depressive disorder
• Extended-release formulation allows for once-daily dosing, improving adherence and maintaining steady-state plasma concentrations
• Lower incidence of extrapyramidal symptoms compared to typical antipsychotics
• May improve sleep architecture due to potent histamine receptor blockade

Common use

Seroquel is commonly prescribed for the management of psychiatric conditions characterized by dysregulation of thought, mood, and behavior. Its primary FDA-approved indications include treatment of schizophrenia in adults and adolescents aged 13 years and older; acute manic and depressive episodes associated with bipolar I disorder; and adjunctive therapy to antidepressants in major depressive disorder. Off-label uses may include treatment of anxiety disorders, insomnia, and agitation in dementia (though latter use carries boxed warning for increased mortality in elderly patients with dementia-related psychosis). Clinical response typically emerges within 1-2 weeks for manic symptoms and 2-4 weeks for depressive and psychotic symptoms.

Dosage and direction

Dosage must be individualized based on clinical condition, response, and tolerability. For schizophrenia: Initial dose 25 mg twice daily, titrated to 300-400 mg daily by day 4, with effective dose range of 150-750 mg/day. For bipolar mania: Initial dose 50 mg twice daily, titrated to 400 mg/day by day 4 (doses up to 800 mg/day may be used). For bipolar depression: Initial dose 50 mg at bedtime, titrated to 300 mg/day by day 4. For adjunctive treatment of MDD: Initial dose 50 mg/day, titrated to 150-300 mg/day. Extended-release formulation allows for once-daily dosing, preferably in evening due to sedative effects. Tablets should be swallowed whole without crushing or chewing.

Precautions

Patients should be monitored for emergence of suicidal ideation, particularly during initial treatment and dosage adjustments. Regular assessment of weight, waist circumference, blood glucose, and lipid profile is recommended due to metabolic risks. Orthostatic hypotension may occur, especially during initial titration—caution advised with rapid dose escalation. Sedation may impair mental/physical abilities required for hazardous tasks. Use with caution in patients with cardiovascular disease, cerebrovascular disease, or conditions predisposing to hypotension. Elderly patients with dementia-related psychosis treated with antipsychotics are at increased risk of death—not approved for this use. Discontinuation should involve gradual tapering to avoid withdrawal symptoms.

Contraindications

Hypersensitivity to quetiapine or any component of the formulation. Concomitant use with strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, HIV protease inhibitors, clarithromycin) due to significantly increased quetiapine exposure. History of neuroleptic malignant syndrome or tardive dyskinesia. Severe hepatic impairment. Not recommended in patients with known prolongation of the QT interval or concomitant use of other drugs that prolong QT interval. Avoid use in patients with conditions associated with severe hypotension.

Possible side effect

Common adverse reactions (≥10%): Somnolence (18-57%), dry mouth (9-44%), dizziness (10-18%), constipation (7-11%), weight gain (5-23%), dyspepsia (5-10%). Serious side effects requiring medical attention: Neuroleptic malignant syndrome (hyperpyrexia, muscle rigidity, autonomic instability), tardive dyskinesia (involuntary movements), metabolic changes (hyperglycemia, dyslipidemia), orthostatic hypotension, syncope, cataracts (regular eye examinations recommended), leukopenia/neutropenia, seizures, cognitive and motor impairment, dysphagia. Percentage estimates vary by indication and dosage.

Drug interaction

Strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, ritonavir) increase quetiapine exposure—dose reduction required. CYP3A4 inducers (e.g., carbamazepine, phenytoin, rifampin, St. John’s wort) decrease quetiapine exposure—dose increase may be needed. May enhance effects of antihypertensive agents due to α1-adrenergic blockade. May potentiate CNS depression with alcohol, benzodiazepines, and other sedating agents. May antagonize levodopa and dopamine agonists. Concurrent use with other drugs that prolong QT interval (e.g., class IA/III antiarrhythmics, antipsychotics, antibiotics) may increase risk of cardiac arrhythmias.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is close to the time of the next scheduled dose. In that case, the missed dose should be skipped and the regular dosing schedule resumed. Patients should not take double or extra doses to make up for a missed dose. For the extended-release formulation, if remembered within 6 hours of scheduled time, take immediately; if beyond 6 hours, skip and resume normal schedule next day.

Overdose

Symptoms may include sedation, tachycardia, hypotension, respiratory depression, coma, and elevated creatine phosphokinase. Fatalities have been reported with quetiapine overdose, particularly in combination with other drugs. Management involves supportive care with continuous cardiac monitoring due to risk of QT prolongation and arrhythmias. Gastric lavage may be considered if presented early. Activated charcoal may be effective. There is no specific antidote; hemodialysis is unlikely to be beneficial due to high protein binding. Contact poison control center for latest guidance.

Storage

Store at room temperature (15-30°C/59-86°F) in original container. Protect from moisture and light. Keep tightly closed. Do not remove desiccant from bottle. Keep out of reach of children and pets. Do not use beyond expiration date printed on packaging. Properly dispose of unused medication through take-back programs or following FDA-recommended disposal methods.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Seroquel is a prescription medication that should be used only under the supervision of a qualified healthcare professional. Individual response to medication may vary. Patients should not initiate, discontinue, or change dosage without consulting their prescribing physician. The complete prescribing information including boxed warnings should be reviewed before administration. Healthcare providers should assess risks and benefits based on individual patient factors.

Reviews

Clinical trials demonstrate significant improvement in PANSS scores for schizophrenia (mean reduction 15-20 points vs placebo), Young Mania Rating Scale scores (improvement of 12-15 points vs placebo in bipolar mania), and Montgomery-Åsberg Depression Rating Scale scores (improvement of 5-7 points vs placebo in bipolar depression). Real-world evidence supports maintenance of effect with long-term use, though metabolic side effects remain a concern requiring ongoing monitoring. Patient-reported outcomes indicate improved quality of life and functional capacity when effective, though sedation and weight gain are frequently cited reasons for discontinuation. Comparative effectiveness studies show similar efficacy to other atypical antipsychotics with differing side effect profiles.