How long does Seroquel (quetiapine) last in the body?

Duration of Quetiapine (Seroquel) in the Body

Quetiapine has an elimination half-life of approximately 6-7 hours, meaning it takes about 30-35 hours (5 half-lives) to be completely eliminated from the body after the last dose. 1, 2

Pharmacokinetic Profile

Absorption and Peak Levels:

• Quetiapine is rapidly absorbed after oral administration, reaching maximum plasma concentrations within 1-2 hours 1, 2
• The drug demonstrates nearly complete bioavailability from oral tablets, with food having minimal effects on absorption 2

Elimination Characteristics:

• The mean terminal half-life is approximately 7 hours, though some sources report it as close to 6 hours 1, 3, 2
• After 5 half-lives (approximately 30-35 hours), the drug is considered essentially eliminated from the body 2
• Elimination occurs primarily through hepatic metabolism via cytochrome P450 3A4 1, 2
• After administration of radiolabeled quetiapine, approximately 73% is excreted in urine and 21% in feces, with less than 1% excreted as unchanged drug 2

Clinical Duration of Action

Despite the relatively short half-life, the clinical effects may persist longer than plasma levels would predict:

• Dopamine D2 receptor occupancies correlate poorly with plasma concentrations, meaning plasma half-life may not accurately predict duration of clinical effect 4
• At 12 hours after the final dose of a 4-week course, dopamine D2 receptor occupancy was 27% and serotonin 5-HT2 receptor occupancy was 58% 1
• This receptor occupancy data suggests some pharmacological activity persists beyond what the 6-7 hour half-life would indicate

Dosing Implications

The short half-life has important clinical implications:

• Quetiapine can be effectively administered twice daily (every 12 hours) rather than three times daily, as demonstrated in clinical trials showing no significant efficacy differences between 225 mg twice daily and 150 mg three times daily 4
• The recommended target dosage is 300-450 mg/day administered in two divided doses 1
• Treatment should be initiated at 50 mg/day with daily incremental adjustments until target dose is reached by day 4 1

Special Population Considerations

Elimination is prolonged in certain populations:

• Oral clearance declines with age, with elderly patients showing 20-30% higher plasma concentrations and up to 50% lower clearance than younger patients 1
• Mean oral clearance is reduced by approximately 25% in patients with hepatic cirrhosis or severe renal impairment 1
• A starting dose of 25 mg/day with daily increases of 25-50 mg is recommended for elderly patients and those with hepatic or renal impairment 1

Drug Interactions Affecting Duration

Several medications can alter quetiapine elimination:

• Phenytoin and thioridazine increase quetiapine clearance (shortening duration in the body), requiring dosage adjustment 2
• Ketoconazole decreases clearance (prolonging duration in the body) 2
• Cigarette smoking does not appear to alter quetiapine pharmacokinetics 2