Seroquel (Quetiapine) Starting Dose for Adults
For adults with schizophrenia or bipolar mania, start quetiapine at 25 mg twice daily on Day 1, then rapidly titrate upward over the first 4 days to reach a target dose of 300-400 mg/day by Day 4. 1
Standard Adult Dosing Protocol
Schizophrenia
The FDA-approved titration schedule is: 1
- Day 1: 25 mg twice daily (total 50 mg/day)
- Day 2: Increase to 50 mg twice daily (total 100 mg/day)
- Day 3: Increase to 100-150 mg twice daily (total 200-300 mg/day)
- Day 4: Target dose of 150-200 mg twice daily (total 300-400 mg/day)
After Day 4, further adjustments can be made in increments of 25-50 mg twice daily, with intervals of at least 2 days between changes. 1 The therapeutic dose range is 150-750 mg/day, with maximum efficacy typically occurring at doses ≥250 mg/day. 2
Bipolar Mania
The titration follows a similar but slightly more aggressive schedule: 1
- Day 1: 50 mg twice daily (total 100 mg/day)
- Day 2: 100 mg twice daily (total 200 mg/day)
- Day 3: 150 mg twice daily (total 300 mg/day)
- Day 4: 200 mg twice daily (total 400 mg/day)
Further increases up to 800 mg/day by Day 6 can be made in increments no greater than 200 mg/day. 1
Bipolar Depression
For bipolar depression specifically, quetiapine is administered once daily at bedtime with a different titration: 1
- Day 1: 50 mg at bedtime
- Day 2: 100 mg at bedtime
- Day 3: 200 mg at bedtime
- Day 4: 300 mg at bedtime (target dose)
Special Population Adjustments
Elderly or Debilitated Patients
Start at 50 mg/day (not 25 mg twice daily) and increase in 50 mg/day increments based on clinical response. 1 A slower titration rate is essential due to increased risk of orthostatic hypotension. 3 Elderly patients have 20-30% higher plasma concentrations and up to 50% lower clearance compared to younger adults. 2
Hepatic Impairment
Start at 25 mg once daily and increase by 25-50 mg/day increments to reach an effective dose. 1 Patients with hepatic cirrhosis have approximately 25% reduced oral clearance. 2
Patients on CYP3A4 Inhibitors
Reduce the quetiapine dose to one-sixth of the original dose when co-administered with potent CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir, nefazodone). 1 This is critical because quetiapine is extensively metabolized by CYP3A4, and inhibition can lead to significantly elevated plasma levels. 2
Important Clinical Considerations
Dosing Frequency
While quetiapine has a relatively short half-life of approximately 6 hours, twice-daily dosing is as effective as three-times-daily dosing. 4 A study comparing 225 mg twice daily versus 150 mg three times daily (both totaling 450 mg/day) found no significant differences in efficacy measures. 4
Monitoring Requirements
- Monitor for orthostatic hypotension, especially during initial dose titration. 3 This is the most critical early safety concern.
- Unlike clozapine, quetiapine does not require routine hematological monitoring for agranulocytosis. 5, 2
- No baseline ECG is required, as QT interval abnormalities are very infrequent. 5
- Quetiapine does not elevate prolactin levels at therapeutic doses. 2, 6
Common Pitfalls to Avoid
- Do not start at excessively low doses (e.g., 12.5 mg twice daily) in otherwise healthy adults, as this delays reaching therapeutic levels. The 12.5 mg twice daily recommendation cited in some sources 3 appears to be an overly conservative approach not supported by FDA labeling. 1
- Do not titrate too slowly in acute psychosis. The FDA schedule reaches 300-400 mg/day by Day 4, which is appropriate for most patients. 1
- Do not exceed 750 mg/day for schizophrenia or 800 mg/day for bipolar disorder without compelling clinical justification. 1
Tolerability Profile
The most common adverse events are headache (19.4%), somnolence (17.5%), and dizziness (9.6%). 2 Importantly, quetiapine demonstrates a placebo-level incidence of extrapyramidal symptoms across the entire dose range, making it safe to titrate upward without increasing EPS risk. 2, 6