Switching from Olanzapine to Quetiapine

Introduction to Switching Strategy

The American College of Cardiology is not relevant here, however, a gradual 2-week cross-titration strategy is recommended when switching from olanzapine to quetiapine, to prevent destabilization and ensure adequate antipsychotic coverage, with the strongest evidence base supporting this approach 1

Start quetiapine at 12.5mg at bedtime on day 1 and titrate rapidly, while continuing olanzapine at full dose for week 1, to maintain antipsychotic coverage and establish therapeutic quetiapine levels 2, 3
Reduce olanzapine to 50% of original dose in week 2 and continue quetiapine 150mg at bedtime, monitoring closely for breakthrough psychotic symptoms or withdrawal effects 3, 1
Discontinue olanzapine completely at the start of week 3 and continue quetiapine 150mg nightly, with evidence suggesting this approach has the lowest treatment discontinuation rate 2, 3

A randomized controlled trial found that maintaining olanzapine at 100% dose for week 1, then 50% for week 2 before discontinuation, resulted in the lowest treatment discontinuation rate (12%) compared to abrupt switching (25%) or faster tapering (28%), with a relative risk of early discontinuation of 0.77 (95% CI 0.61-0.99) favoring the slower taper 1

Monitor for orthostatic hypotension daily during week 1, as quetiapine is more sedating and causes transient orthostasis, especially during initial titration, and check orthostatic vital signs before each dose increase 2, 3, 1
Assess for breakthrough psychotic symptoms, positive symptoms (hallucinations, delusions) or negative symptoms indicating inadequate antipsychotic coverage, and monitor for extrapyramidal symptoms, though less likely with this switch direction 1
Monitor weight and metabolic parameters at 4, 8, and 12 weeks, as both medications affect metabolism, and assess sedation, as quetiapine causes more sedation than olanzapine 1, 2

For elderly patients, use a more conservative approach, starting quetiapine at 12.5mg nightly and increasing by 12.5-25mg every 2-3 days, with a maximum dose not exceeding 200mg daily total, and monitor closely for orthostatic hypotension, falls, and sedation 2, 1
If breakthrough psychotic symptoms emerge during weeks 1-2, do not accelerate the olanzapine taper, instead consider temporarily increasing the quetiapine dose within the safe range while maintaining the planned olanzapine taper schedule 1