Switching from Wellbutrin 400mg to an SSRI: Equivalent Dosing Guidelines
There is no direct equivalent SSRI dosing when switching from Wellbutrin (bupropion) 400mg, as these medications work through completely different mechanisms of action. Bupropion primarily affects dopamine and norepinephrine neurotransmission, while SSRIs target serotonin pathways 1, 2.
Recommended SSRI Starting Dosages When Switching from Wellbutrin
When transitioning from Wellbutrin 400mg to an SSRI, follow these starting dosages:
- Citalopram: Start at 20mg daily 1
- Escitalopram: Start at 10mg daily 1
- Fluoxetine: Start at 20mg daily 1
- Paroxetine: Start at 20mg daily 1
- Sertraline: Start at 50mg daily 1
Cross-Titration Approach
A cross-titration approach is recommended when switching from Wellbutrin to an SSRI:
- Begin the SSRI at the starting dose while maintaining Wellbutrin 400mg 1
- After 1 week, reduce Wellbutrin to 300mg while continuing the SSRI 2
- After another week, reduce Wellbutrin to 200mg 2
- After a third week, reduce Wellbutrin to 100mg 2
- After a fourth week, discontinue Wellbutrin completely 2
SSRI Selection Considerations
When choosing which SSRI to switch to, consider these factors:
- Sertraline has less effect on metabolism of other medications compared to other SSRIs 1
- Citalopram/Escitalopram may have the least effect on CYP450 isoenzymes and lower propensity for drug interactions 1
- Paroxetine has more anticholinergic effects and should be avoided in older adults 1
- Fluoxetine has a greater risk of agitation and overstimulation 1
Important Precautions
- Monitor for serotonin syndrome, especially during the cross-titration period. Symptoms include mental status changes, autonomic instability, neuromuscular abnormalities, and gastrointestinal symptoms 1, 3
- Sexual dysfunction is more common with SSRIs than with bupropion 4, 5
- Discontinuation symptoms are more common with paroxetine, fluvoxamine, and sertraline 1
- QT prolongation is a risk with citalopram at doses exceeding 40mg/day 1
Duration of Treatment
- An adequate trial of SSRI treatment requires 4-8 weeks 1
- For first episodes of depression, treatment should continue for 4-12 months after remission 1
- For recurrent depression, longer treatment may be necessary 1
Common Pitfalls to Avoid
- Abrupt discontinuation of Wellbutrin can lead to withdrawal symptoms; always taper gradually 2
- Starting SSRIs at too high a dose can increase initial side effects; begin with recommended starting doses 1
- Failure to monitor for drug interactions, particularly with medications metabolized by CYP450 enzymes 1
- Overlooking the potential for serotonin syndrome when cross-titrating, especially if other serotonergic medications are involved 1, 3
Remember that while Wellbutrin and SSRIs have similar efficacy for depression, they have different side effect profiles. SSRIs are associated with more sexual dysfunction, while Wellbutrin may cause more dry mouth and insomnia 4.