Switching from Lexapro 20mg to Prozac: Recommended Tapering Schedule
When switching from Lexapro (escitalopram) 20mg to Prozac (fluoxetine), a gradual cross-tapering approach over 3 weeks is recommended to minimize withdrawal symptoms and ensure therapeutic coverage. 1
Cross-Tapering Protocol
Week 1:
- Reduce Lexapro from 20mg to 10mg daily
- Start Prozac at 10mg every other day 1
Week 2:
- Further reduce Lexapro to 5mg daily
- Increase Prozac to 10mg daily 1
Week 3:
- Discontinue Lexapro completely
- Continue Prozac at 10mg daily, with the option to increase to 20mg if clinically indicated 1
Rationale for This Approach
- Fluoxetine's very long half-life (2-3 days for parent compound, 7-9 days for active metabolite) makes it uniquely suited for transitions from other SSRIs as it provides a more gradual offset of serotonergic activity 1
- Cross-tapering is preferred over abrupt switching to minimize discontinuation symptoms, which occur in up to 79% of patients who stop antidepressants 2
- Gradual tapering is essential as escitalopram discontinuation syndrome can include dizziness, muscle tension, chills, confusion, and concentration problems 3
Important Considerations
- Higher doses and plasma concentrations of escitalopram are associated with increased risk of discontinuation syndrome, making the gradual taper especially important for a 20mg dose 3
- Fluoxetine is more activating than escitalopram, which may benefit patients with fatigue but could potentially worsen anxiety or insomnia 1
- Take fluoxetine in the morning rather than evening if activation symptoms occur 1
- Due to fluoxetine's long half-life, side effects may not manifest for several weeks after starting or increasing the dose 1
Monitoring and Follow-up
- Schedule follow-up within 1-2 weeks after completing the transition to monitor for adverse effects and treatment response 1
- Be aware that full therapeutic response to fluoxetine may take 4-8 weeks to develop 1
- If severe withdrawal symptoms occur despite tapering, consider temporarily returning to the previous dose and tapering more slowly 4
- For patients experiencing severe symptoms during the transition, temporary use of a benzodiazepine may be considered if no contraindications exist 1