Augment with Aripiprazole
For an adult with major depressive disorder who has not improved after at least six weeks of an SSRI or SNRI, augmentation with aripiprazole is superior to switching to fluoxetine. The most recent high-quality evidence demonstrates that aripiprazole augmentation produces significantly better outcomes than switching antidepressants, with response rates of 60% versus 32.6% and remission rates of 54% versus 19.6% 1.
Evidence Supporting Aripiprazole Augmentation
The strongest evidence comes from a 2015 randomized, rater-blinded trial directly comparing aripiprazole augmentation versus antidepressant switching in 101 patients with inadequate response to initial antidepressants 1. This study showed:
- Significantly greater improvement in depression scores with aripiprazole augmentation (MADRS difference of -8.7 points, p<0.0001)
- Earlier response, with differences evident by week 2
- Nearly double the response rate (60% vs 32.6%, p=0.0086)
- Nearly triple the remission rate (54% vs 19.6%, p=0.0005)
- Comparable tolerability between groups
A 2014 naturalistic study of 295 patients reinforced these findings, showing that aripiprazole augmentation (74.1% improvers) significantly outperformed antidepressant combination therapy (48.1%, p<0.001) and performed similarly to switching (73.5%) 2. Notably, patients themselves preferred augmentation (52.9%) over switching (15.6%) when given the choice.
The 2023 OPTIMUM trial in older adults (≥60 years) provides additional support, demonstrating that aripiprazole augmentation improved well-being significantly more than switching to bupropion (difference 2.79 points, p=0.014), with remission rates of 28.9% versus 19.3% 3.
Why Not Switch to Fluoxetine?
The ACP guidelines explicitly state that "insufficient evidence exists to prefer one agent over another as second-line therapy" when switching antidepressants 4. Multiple studies show no difference in efficacy when switching from one SSRI to another 5. Fluoxetine specifically has no demonstrated superiority over other SSRIs for treatment-resistant depression.
Switching strategies have several disadvantages:
- Delayed response due to washout periods and titration of new medication
- Loss of any partial benefit from the current antidepressant
- No better outcomes than augmentation in head-to-head trials
- Fluoxetine's long half-life (2-7 days for fluoxetine, 4-15 days for norfluoxetine) complicates future medication changes 6
Practical Implementation
Dosing strategy:
- Start aripiprazole at 2-5 mg daily 7
- The optimal dose range appears to be 2-5 mg, with efficacy plateauing beyond this range
- Maximum benefit achieved without requiring higher licensed doses (up to 20 mg)
- Mean effective dose in clinical studies: 6.9 mg daily 8
Timeline:
Monitoring:
- Watch for akathisia (most common adverse effect requiring discontinuation)
- Monitor weight and metabolic parameters
- Assess for sedation, particularly in first weeks
- Tolerability is generally good, with only 5.7% discontinuation due to adverse events 8
Clinical Caveats
When switching might be preferred:
- Patient refuses antipsychotic medication
- Significant metabolic concerns (diabetes, obesity)
- History of extrapyramidal symptoms with antipsychotics
- Access/cost barriers to aripiprazole
Important considerations:
- The 2016 ACP guidelines note insufficient evidence for direct comparisons of switching versus augmentation strategies 5
- However, the subsequent research (2015-2024) consistently favors augmentation
- The 2024 ASCERTAIN-TRD trial showed repetitive transcranial magnetic stimulation augmentation superior to switching, further supporting augmentation strategies over switching 9
Alternative if aripiprazole fails or is not tolerated:
- Consider lithium augmentation (18.9% remission rate in older adults) 3
- Bupropion augmentation (28.2% remission rate) 3
- Cognitive behavioral therapy augmentation 5
The evidence strongly supports augmentation over switching as the next-step strategy, with aripiprazole demonstrating the most robust efficacy data in treatment-resistant depression.