Switching from Olanzapine 10mg BD to Quetiapine 150mg Nocte
The patient can switch using a gradual cross-titration over 1-2 weeks, starting quetiapine at the target dose of 150mg nocte while tapering olanzapine by 50% in the first week, then discontinuing it completely in the second week. 1
Recommended Cross-Titration Protocol
Week 1:
- Start quetiapine 150mg at bedtime 1
- Reduce olanzapine from 10mg BD (20mg total daily) to 10mg once daily (50% reduction) 2, 3
- This overlap period allows assessment of quetiapine tolerability while minimizing withdrawal symptoms from olanzapine 2, 3
Week 2:
Evidence Supporting This Approach
The most recent international schizophrenia guidelines explicitly recommend that antipsychotic switching should involve gradual cross-titration informed by the half-life and receptor profile of each medication, rather than abrupt discontinuation 1. This principle is critical because both olanzapine and quetiapine have different pharmacodynamic profiles that require careful transition management.
A randomized controlled trial specifically examining olanzapine discontinuation strategies found that gradual reduction over 2 weeks was associated with significantly lower discontinuation rates (12%) compared to abrupt switching (25%) or faster tapers (28%), with a relative risk reduction of 0.77 for treatment retention 2. This study demonstrated that the slowest olanzapine taper (100% dose for week 1, then 50% for week 2, then stop) resulted in the best outcomes.
Another randomized study comparing switching strategies found that gradual antipsychotic discontinuation combined with immediate initiation of the full therapeutic dose of the new agent had the most favorable efficacy and tolerability profile, with over 90% of patients improved or clinically unchanged by week 3 3.
Important Clinical Considerations
Dosing Context:
- Quetiapine 150mg nocte is a relatively low dose (therapeutic range for schizophrenia is typically 400-800mg daily) 1
- If this switch is for sedation/sleep rather than psychosis control, the lower dose is appropriate 4
- Olanzapine 10mg BD (20mg total daily) is a moderate-to-high dose, so adequate cross-coverage is essential 2, 3
Common Pitfalls to Avoid:
- Do not abruptly stop olanzapine - this doubles the risk of treatment discontinuation and symptom worsening 2
- Do not use a "washout period" between medications - continuous antipsychotic coverage is essential 3
- Monitor closely for withdrawal symptoms during the first 2 weeks, including insomnia, nausea, anxiety, and psychotic symptom emergence 2, 5
- Watch for sedation as quetiapine has significant sedating properties, especially when combined with residual olanzapine 4
Monitoring Requirements:
- Assess for symptom stability at days 3-7 and again at week 2 during the cross-taper 2, 5
- Monitor for extrapyramidal symptoms, though both medications have relatively low EPS risk 5, 3
- Track metabolic parameters as both agents carry metabolic risks, though the switch may improve weight if that was an olanzapine side effect 2, 3
Alternative Faster Approach (If Clinically Necessary):
If urgent switching is required due to severe side effects, a 1-week cross-taper can be considered: start quetiapine 150mg nocte while reducing olanzapine to 50% for 3-4 days, then discontinuing 3. However, this carries higher risk of symptom destabilization 2.