How to switch from 20mg olanzapine (olanzapine) to quetiapine (quetiapine)?

Switching from 20mg Olanzapine to Quetiapine

When switching from 20mg olanzapine to quetiapine, the recommended approach is a cross-titration method starting with quetiapine 25mg twice daily while gradually reducing olanzapine over 1-2 weeks to minimize risk of relapse or withdrawal symptoms. 1

Dose Equivalence and Initial Dosing

• 20mg of olanzapine is approximately equivalent to 400mg of quetiapine based on minimum effective dose equivalence ratios 2
• Begin with quetiapine immediate release 25mg twice daily (50mg total daily dose) while maintaining the current olanzapine dose 3
• Quetiapine should be titrated upward gradually using the following schedule (administered in divided doses twice daily):
  • Day 1: 50mg total
  • Day 2: 100mg total
  • Day 3: 200mg total
  • Day 4: 300mg total
  • Day 5: 400mg total 3, 1

Cross-Titration Schedule

• Week 1: Start quetiapine at 25mg twice daily while reducing olanzapine to 15mg daily 1, 4
• Week 2: Increase quetiapine to 100-200mg total daily dose while reducing olanzapine to 10mg daily 1
• Week 3: Increase quetiapine to 300-400mg total daily dose while reducing olanzapine to 5mg daily 1
• Week 4: Discontinue olanzapine completely while maintaining quetiapine at target dose (typically 400-600mg daily) 1

Monitoring During Transition

• Monitor closely for return of psychotic symptoms during the transition period 5
• Watch for potential side effects of quetiapine including sedation, orthostatic hypotension, and dizziness 6
• Quetiapine is less likely to cause extrapyramidal side effects than other atypical antipsychotics 6
• Assess for any withdrawal symptoms from olanzapine reduction 5

Special Considerations

• For elderly patients or those with hepatic impairment, use lower starting doses of quetiapine (25mg daily) and titrate more slowly 3
• If the patient is taking any CYP3A4 inhibitors (e.g., ketoconazole, itraconazole), reduce the quetiapine dose to one-sixth of the normal dose 3
• If the patient is taking any CYP3A4 inducers (e.g., phenytoin, carbamazepine), the quetiapine dose may need to be increased up to 5-fold 3
• Avoid combining either medication with benzodiazepines when possible, as fatalities have been reported with concurrent use of benzodiazepines with high-dose olanzapine 6

Maintenance Dosing

• The typical effective maintenance dose range for quetiapine is 150-750mg daily, administered in divided doses 1
• The target dose should be individualized based on clinical response and tolerability 3
• Most patients require 400-600mg daily for optimal symptom control 7

Common Pitfalls to Avoid

• Avoid abrupt discontinuation of olanzapine, which can lead to rebound psychosis or withdrawal symptoms 5, 4
• Do not start quetiapine at too high a dose, as this increases risk of sedation and orthostatic hypotension 6
• Ensure adequate hydration during the transition to minimize risk of orthostatic hypotension 6
• Be aware that both medications can cause weight gain, though the pattern and extent may differ between agents 7