What is the half-life of Seroquel (quetiapine)?

Half-Life of Seroquel (Quetiapine)

The elimination half-life of quetiapine is approximately 6-7 hours in healthy adults, requiring twice or three times daily dosing to maintain therapeutic plasma levels. 1, 2

Pharmacokinetic Profile

• Standard half-life: Quetiapine has a mean terminal half-life of approximately 7 hours in healthy individuals 2
• Dosing implications: The relatively short half-life of approximately 6 hours necessitates administration in divided doses (typically twice or three times daily) to maintain clinical efficacy 1, 3
• Peak concentrations: Maximum plasma concentrations occur 1-2 hours after oral administration 1, 2

Special Population Considerations

Elderly Patients

• Clearance reduction: Oral clearance values are up to 50% lower in elderly patients compared to younger adults 1
• Increased exposure: Maximum steady-state plasma concentrations and area under the curve values are approximately 20-30% higher in elderly patients 1
• Clinical implication: Lower starting doses (25 mg/day) with slower titration are recommended in elderly patients 1

Hepatic Impairment

• Reduced clearance: Mean oral clearance is reduced by approximately 25% in patients with hepatic cirrhosis compared to healthy controls 1
• Dosing adjustment: Start with 25 mg/day and increase by 25-50 mg increments to reach effective dose 1

Renal Impairment

• Minimal impact: Severe renal impairment reduces clearance by approximately 25%, but this is less pronounced than hepatic effects 1
• Caution advised: Use with caution and consider lower starting doses (25 mg/day) 1

Clinical Dosing Context

• Target dose range: The recommended target dosage is 300-450 mg/day administered in 2 divided doses, with a therapeutic range of 150-750 mg/day 1
• Twice daily efficacy: Clinical trials demonstrate that 225 mg twice daily is as effective as 150 mg three times daily, supporting twice-daily administration despite the short half-life 4
• Metabolism: Quetiapine is predominantly metabolized by cytochrome P450 3A4, and the parent drug accounts for less than 1% of excreted radioactivity 2

Drug Interactions Affecting Half-Life

• CYP3A4 inducers: Phenytoin, carbamazepine, barbiturates, and thioridazine increase quetiapine clearance, potentially shortening effective duration of action and requiring dosage adjustment 3, 2
• CYP3A4 inhibitors: Ketoconazole decreases clearance, potentially prolonging drug exposure 2