After the patient’s last 20 mg dose of fluoxetine today, can I start Auvelity (dextromethorphan/bupropion) immediately at bedtime once daily for 10 days then twice daily, or should I wait for a wash‑out period, and how should I manage her returning anhedonia and lethargy?

Immediate Transition from Fluoxetine to Auvelity: Washout Requirements and Management

Direct Answer

You cannot start Auvelity immediately after the last dose of fluoxetine—you must wait at least 14 days after discontinuing fluoxetine before initiating Auvelity due to the risk of serotonin syndrome and MAOI-like interactions. 1

Washout Period Requirements

Why a Washout is Mandatory

• Auvelity contains bupropion, which inhibits CYP2D6, the enzyme responsible for metabolizing both dextromethorphan and SSRIs like fluoxetine 1, 2
• Fluoxetine has an exceptionally long half-life (4-6 days for fluoxetine, 4-16 days for its active metabolite norfluoxetine), meaning it remains in the system for weeks after discontinuation
• The combination of bupropion with SSRIs carries documented risk of serotonin syndrome, with at least one case report of severe serotonin syndrome occurring with therapeutic doses of bupropion and sertraline that progressed to altered consciousness and dysautonomia 3
• The FDA label explicitly states that at least 14 days must elapse between discontinuation of an MAOI or serotonergic agent and initiation of Auvelity to prevent serious drug interactions 1

Specific Washout Timeline

• Wait a minimum of 14 days after the last 20 mg fluoxetine dose before starting Auvelity 1
• Given fluoxetine's long half-life, some clinicians may consider waiting up to 5 weeks for complete elimination, though the FDA-mandated minimum is 14 days 1

Managing Returning Anhedonia and Lethargy During Washout

Bridging Strategy Options

• Consider a short course of a non-serotonergic agent during the washout period if symptoms are severe and functionally impairing
• Increase psychotherapy frequency during the transition period to provide additional support 4
• Monitor closely for worsening depression or suicidal ideation, as the FDA requires assessment within 1-2 weeks of any antidepressant change, with particular attention during the first 1-2 months when suicide risk is highest 4, 1

Symptomatic Management

• Educate the patient that withdrawal symptoms from fluoxetine are typically mild due to its long half-life, but anhedonia and lethargy may represent return of depressive symptoms rather than withdrawal
• Implement behavioral activation strategies to combat anhedonia during the washout period
• Ensure adequate sleep hygiene and exercise as non-pharmacologic interventions for lethargy

Auvelity Initiation Protocol (After 14-Day Washout)

Dosing Schedule

• Start with one tablet (45 mg dextromethorphan/105 mg bupropion) once daily in the morning 1
• After 3 days (not 10 days as you proposed), increase to one tablet twice daily, separated by at least 8 hours 1
• Your proposed 10-day titration is not consistent with FDA labeling; the standard is 3 days 1
• Do not exceed two doses within the same day 1

Pre-Treatment Screening Required

Before starting Auvelity, you must 1:

• Assess blood pressure and monitor periodically during treatment
• Screen for personal or family history of bipolar disorder, mania, or hypomania
• Confirm the patient is not taking any other medications containing bupropion or dextromethorphan
• Screen for seizure disorder, current/prior bulimia or anorexia nervosa (both are contraindications) 1

Administration Details

• Swallow tablets whole; do not crush, divide, or chew 1
• Can be taken with or without food 1

Expected Timeline for Symptom Improvement

• Significant improvement in depressive symptoms may be observed as early as week 1-2 after starting Auvelity, which is faster than traditional SSRIs 5, 2, 6
• Response rates (≥50% reduction in depression scores) at 6 weeks were 60.5% in clinical trials 2
• Remission rates approached 46.5% at 6 weeks and 70% in long-term studies 2, 6

Common Pitfalls to Avoid

• Do not start Auvelity immediately after fluoxetine—the 14-day washout is non-negotiable 1
• Do not use the 10-day once-daily titration you proposed—FDA labeling specifies 3 days before increasing to twice daily 1
• Do not miss the pre-treatment blood pressure assessment—hypertension is a known risk 1
• Do not overlook screening for eating disorders or seizure history—these are absolute contraindications 1
• Monitor closely for early signs of serotonin syndrome if any residual serotonergic activity remains, including agitation, confusion, tremor, or autonomic instability 3

Monitoring During Treatment

• Assess patient status within 1-2 weeks of starting Auvelity for therapeutic response, adverse effects, and suicidal ideation 4, 1
• If inadequate response after 6-8 weeks, modify treatment 4
• Most common adverse effects include dizziness, nausea, headache, diarrhea, somnolence, and dry mouth, though these are generally mild-to-moderate 6, 7
• Auvelity is not associated with significant sexual dysfunction or weight gain, which may be advantageous compared to SSRIs 2