What is the normal dosing for Seroquel (quetiapine)?

Normal Dosing for Seroquel (Quetiapine)

For adults with schizophrenia, start quetiapine at 25 mg twice daily on Day 1, increase to 300-400 mg/day by Day 4 (divided 2-3 times daily), with a typical effective dose range of 150-750 mg/day and maximum of 750 mg/day. 1

Standard Adult Dosing by Indication

Schizophrenia

• Day 1: 25 mg twice daily 1
• Day 2-3: Increase by 25-50 mg increments divided 2-3 times daily 1
• Day 4: Target 300-400 mg/day 1
• Maintenance: 150-750 mg/day (maximum 750 mg/day) 1
• Further adjustments can be made in 25-50 mg increments at intervals of at least 2 days 1
• Clinical efficacy is dose-related, with maximum effects at ≥250 mg/day 2

Bipolar Mania (Adults)

• Day 1: 100 mg/day (divided twice daily) 1
• Day 2: 200 mg/day 1
• Day 3: 300 mg/day 1
• Day 4: 400 mg/day 1
• Maintenance: 400-800 mg/day (maximum 800 mg/day) 1
• Adjustments up to 800 mg/day by Day 6 in increments ≤200 mg/day 1

Bipolar Depression (Adults)

• Once daily at bedtime dosing: 1
• Day 1: 50 mg 1
• Day 2: 100 mg 1
• Day 3: 200 mg 1
• Day 4: 300 mg (target and maximum dose) 1, 3

Dosing Frequency Considerations

Quetiapine can be administered twice daily rather than three times daily without loss of efficacy. 4

• Studies demonstrate 225 mg twice daily is equivalent to 150 mg three times daily for a total of 450 mg/day 4
• The relatively short 6-hour half-life does not necessitate three-times-daily dosing, as dopamine D2 receptor occupancy correlates poorly with plasma concentrations 4

Special Population Adjustments

Elderly Patients

• Start at 50 mg/day 1
• Increase in 50 mg/day increments based on response and tolerability 1
• Alternative recommendation: 12.5 mg twice daily for psychiatric conditions or delirium, with maximum 200 mg twice daily 5
• Slower titration required due to risk of orthostatic hypotension and increased sedation 5, 6

Hepatic Impairment

• Start at 25 mg/day 1
• Increase daily in 25-50 mg/day increments to effective dose 1
• Mean oral clearance reduced by approximately 25% in hepatic cirrhosis 7
• Dose escalation should be performed with caution due to inter-subject variability in clearance 7

Renal Impairment

• No dosage adjustment necessary 7
• Mean oral clearance reduced by approximately 25% in severe renal impairment, but this is not clinically significant 7

Drug Interaction Dose Modifications

With CYP3A4 Inhibitors (e.g., ketoconazole, ritonavir)

• Reduce quetiapine dose to one-sixth of original dose 1
• When inhibitor discontinued, increase quetiapine by 6-fold 1

With CYP3A4 Inducers (e.g., phenytoin, carbamazepine, rifampin)

• Increase quetiapine up to 5-fold of original dose for chronic treatment (>7-14 days) 1
• Titrate based on clinical response and tolerability 1
• When inducer discontinued, reduce to original level within 7-14 days 1

Critical Safety Monitoring

• Monitor for orthostatic hypotension during initial titration, particularly in elderly patients and those on CNS depressants 6
• Quetiapine can be taken with or without food 1
• Avoid abrupt discontinuation to prevent withdrawal symptoms 6
• For patients off quetiapine >1 week, restart with initial dosing schedule 1

Common Pitfalls

• The "high-dose theory" suggesting dosages >800 mg/day are necessary lacks robust controlled data support; standard dosage ranges (150-750 mg/day for schizophrenia) are appropriate for clinical use 8
• Despite the 6-hour half-life, twice-daily dosing is sufficient and improves compliance 4
• Even low doses (12.5 mg) can cause significant sedation in some patients, particularly elderly 9