What dose of Seroquel (quetiapine) should be used when switching from olanzapine 15 mg at bedtime?

Switching from Olanzapine 15 mg to Quetiapine: Dosing Recommendations

When switching from olanzapine 15 mg at bedtime to quetiapine, start with quetiapine 25 mg twice daily (50 mg total) and gradually increase to 300-400 mg daily in divided doses over 1-2 weeks while tapering olanzapine.

Recommended Switching Strategy

Initial Dosing

• Start with quetiapine immediate-release 25 mg twice daily 1
• For the first week, maintain olanzapine at 15 mg while introducing quetiapine (gradual cross-titration) 2

Titration Schedule

1. Week 1:

   • Continue olanzapine 15 mg at bedtime
   • Start quetiapine 25 mg twice daily
   • Increase to 50 mg twice daily by end of week if tolerated

2. Week 2:

   • Reduce olanzapine to 7.5 mg at bedtime
   • Increase quetiapine to 100 mg twice daily (200 mg total)

3. Week 3:

   • Discontinue olanzapine
   • Increase quetiapine to target dose of 150-200 mg twice daily (300-400 mg total)

Evidence-Based Rationale

The gradual cross-titration approach is supported by clinical evidence showing that gradual discontinuation of the previous antipsychotic while initiating the new one results in better outcomes. Research demonstrates that the slowest olanzapine dose reduction strategy (over 2 weeks) was associated with the lowest treatment discontinuation rate (12%) compared to more abrupt switching strategies (25-28%) 2.

Studies specifically examining switches from olanzapine to quetiapine show that:

• The mean effective dose of quetiapine after switching from olanzapine is approximately 500 mg/day 3
• Gradual cross-titration minimizes withdrawal symptoms and reduces risk of psychotic relapse 2

Monitoring During Switch

• Week 1: Watch for sedation, orthostatic hypotension, and dizziness (common with quetiapine initiation) 1
• Week 2: Monitor for efficacy as olanzapine is reduced
• Week 3 and beyond: Assess for:
  • Treatment response
  • Sedation (quetiapine is more sedating than olanzapine)
  • Extrapyramidal symptoms (should improve with switch to quetiapine) 3
  • Metabolic parameters (both medications affect these, but profiles differ)

Important Considerations

• Quetiapine has a shorter half-life than olanzapine, requiring twice-daily dosing for optimal effect 1
• Quetiapine is less likely to cause extrapyramidal symptoms than other atypical antipsychotics 1
• Quetiapine may cause orthostatic hypotension, especially during initial titration 1
• Both medications can cause metabolic effects, but the profiles differ slightly

Common Pitfalls to Avoid

• Avoid abrupt discontinuation of olanzapine, which can lead to withdrawal symptoms and higher discontinuation rates 2
• Avoid starting with too high a dose of quetiapine, which increases risk of sedation and orthostatic hypotension
• Don't underdose quetiapine - the therapeutic dose range is typically 300-750 mg/day for schizophrenia and other psychotic disorders 3
• Be cautious in elderly patients or those with hepatic impairment - use lower doses and slower titration 1

This gradual cross-titration approach maximizes the chances of a successful medication transition while minimizing the risk of symptom exacerbation or discontinuation due to adverse effects.