Can Mirtazapine (Remeron) Be Added to Bupropion (Wellbutrin) and Fluoxetine (Prozac)?
Yes, mirtazapine can be safely added to a patient taking both bupropion and fluoxetine, as this combination is pharmacologically rational and supported by evidence for treatment-resistant depression. This triple-antidepressant strategy leverages complementary mechanisms of action and has demonstrated clinical utility in augmentation approaches.
Pharmacological Rationale
The combination is mechanistically sound:
- Fluoxetine (Prozac): SSRI that inhibits serotonin reuptake
- Bupropion (Wellbutrin): Norepinephrine-dopamine reuptake inhibitor with no serotonergic activity 1
- Mirtazapine (Remeron): Noradrenergic and specific serotonergic antidepressant (NaSSA) that blocks alpha-2 presynaptic receptors, enhancing both norepinephrine and serotonin release 1, 2
This creates synergistic neurotransmitter modulation across serotonin, norepinephrine, and dopamine systems without redundant mechanisms.
Evidence for Combination Therapy
Research directly supports mirtazapine combinations with other antidepressants:
- A randomized controlled trial demonstrated that mirtazapine combined with fluoxetine achieved 52% remission rates versus 25% with fluoxetine monotherapy at 6 weeks 3
- The combination of mirtazapine with venlafaxine achieved 58% remission rates in the same study 3
- Mirtazapine augmentation is specifically recommended as a second-step treatment strategy when initial antidepressant therapy fails 4
- Studies show mirtazapine combinations are "generally well tolerated" and can "boost antidepressant response" 5, 6
Safety Considerations
Serotonin Syndrome Risk
While combining multiple serotonergic agents raises theoretical concern for serotonin syndrome, the actual risk is manageable with proper monitoring 7:
- Bupropion has no appreciable serotonergic activity, reducing overall risk 2
- Serotonin syndrome primarily occurs with MAOIs combined with other serotonergic drugs 7, 8
- Start mirtazapine at a low dose (7.5-15 mg at bedtime) and monitor closely in the first 24-48 hours after initiation 7
Monitor for serotonin syndrome symptoms: confusion, agitation, tremors, hyperreflexia, diaphoresis, tachycardia, hypertension 7
Drug-Drug Interactions
Pharmacokinetic interactions are minimal 8:
- Mirtazapine does not significantly affect CYP450 enzymes 8
- Fluoxetine is a CYP2D6 inhibitor but mirtazapine is not primarily metabolized by this pathway 8
- Bupropion and mirtazapine showed no relevant pharmacokinetic interactions in studies 8
Complementary Side Effect Profiles
The combination may actually improve tolerability 3, 6, 9:
- Mirtazapine's sedating effects can counteract bupropion's activating properties and potential insomnia 1, 9
- Mirtazapine's appetite-stimulating effects may offset fluoxetine-related appetite suppression 9
- Bupropion has lower sexual dysfunction rates, potentially mitigating SSRI-related sexual side effects 10, 11, 10
Practical Implementation
Dosing strategy:
- Continue current bupropion and fluoxetine at stable doses
- Start mirtazapine 7.5-15 mg at bedtime 1
- Increase to 30 mg at bedtime after 1-2 weeks if tolerated 1
- Maximum dose: 45 mg daily 1
Monitoring schedule:
- Assess within 1-2 weeks of adding mirtazapine for adverse effects and early response 10
- Continue regular follow-up every few weeks initially 12
- Watch for: excessive sedation, weight gain, serotonin syndrome symptoms 10, 8
Common Pitfalls to Avoid
- Don't start at full dose: Begin with 7.5-15 mg to assess tolerance 1
- Don't ignore sedation: Mirtazapine's sedating effects are dose-dependent and most prominent at lower doses; advise bedtime dosing 1, 12
- Don't overlook weight gain: Mirtazapine commonly causes increased appetite and weight gain—counsel patients proactively 10, 8
- Don't forget to reassess: If no improvement after 6-8 weeks, consider alternative strategies 10
When This Combination Is Particularly Useful
Target this combination for patients with 9:
- Treatment-resistant depression (inadequate response to dual therapy)
- Prominent insomnia (mirtazapine's sedating effects are beneficial)
- Decreased appetite or weight loss (mirtazapine stimulates appetite)
- Anxiety symptoms (mirtazapine has anxiolytic properties) 13
The evidence supports this triple combination as a rational, safe, and potentially more effective strategy than continuing dual therapy alone in treatment-resistant cases.