Washout Period When Switching from Fluoxetine to Escitalopram
No washout period is necessary when switching from fluoxetine to escitalopram—you can stop fluoxetine and start escitalopram 10 mg the following day, allowing the patient to discharge home before their desired date. 1
Why No Washout is Required
Fluoxetine's pharmacokinetic profile makes it unique among SSRIs and eliminates the need for a washout period:
- Fluoxetine has an exceptionally long elimination half-life (including its active metabolite norfluoxetine), which provides a built-in taper effect that minimizes discontinuation syndrome risk 1
- This extended half-life means fluoxetine gradually clears from the system over weeks, creating a natural washout while escitalopram is being initiated 2, 1
- Fluoxetine is the least likely SSRI to cause discontinuation syndrome due to this prolonged half-life 2, 1
Practical Switching Protocol
Direct switch approach:
- Stop fluoxetine abruptly on day 1 1
- Start escitalopram 10 mg daily on day 2 (the following day) 1
- This is the recommended starting and typical effective dose for adults and adolescents 12+ years 1
Safety Considerations During the Switch
Serotonin syndrome risk is low but requires monitoring:
- Monitor closely for serotonin syndrome symptoms during the first 24-48 hours after starting escitalopram (confusion, agitation, tremors, hyperreflexia, tachycardia, diaphoresis) 2, 1
- The risk is minimal with this specific switch because escitalopram has minimal CYP450 enzyme interactions compared to other SSRIs, reducing drug-drug interaction concerns 1
- Watch for behavioral activation, increased anxiety, or agitation—common early SSRI side effects 1
Additional monitoring requirements:
- Assess for suicidal ideation and behavior, particularly in adolescents and young adults during the first few months 1
- Monitor for treatment response using standardized symptom scales at regular intervals 1
- Avoid combining with MAOIs, tramadol, triptans, or other serotonergic drugs 2, 1
Dosing Adjustments if Needed
- Maximum escitalopram dose is 20 mg daily 1
- If dose increases are needed, use 5 mg increments 1
- Escitalopram can interact with drugs that prolong QT interval, though clinical significance at standard doses is minimal 2, 1, 3
Common Pitfall to Avoid
The main error would be unnecessarily delaying the switch with a washout period, which would postpone treatment and potentially worsen depressive symptoms. Research confirms that direct switching from fluoxetine to other SSRIs (including citalopram, escitalopram's parent compound) is well-tolerated without washout 4, 5.