Fatigue Explanation: Aripiprazole is the Primary Culprit
Your increased tiredness is most likely caused by the aripiprazole (Abilify) you just started, not the citalopram (Celexa) dose reduction. Fatigue is one of the most common side effects of aripiprazole, particularly when initiating treatment.
Why Aripiprazole Causes Fatigue
According to FDA labeling data, fatigue occurs in 8% of adults taking aripiprazole as adjunctive treatment for depression (compared to 4% on placebo) 1. The sedation and somnolence rates are even higher:
- Somnolence: 6% (vs 3% placebo)
- Sedation: 4% (vs 2% placebo)
- Lethargy is also documented as a common adverse effect
These sedating effects are dose-related and typically emerge early in treatment—exactly matching your timeline of starting 4mg last week 1.
Why the Celexa Reduction is Unlikely the Cause
Reducing citalopram from 40mg to 20mg would not typically cause increased fatigue. In fact:
- SSRIs like citalopram can themselves contribute to fatigue through increased serotonergic activity 2
- Dose reduction of SSRIs may actually improve fatigue in some patients 2
- Citalopram at 20-40mg has been shown to reduce fatigue in chronic fatigue studies, not worsen it 3
While SSRI discontinuation can cause withdrawal symptoms, you're still taking 20mg (a therapeutic dose), so this is not withdrawal.
What to Expect and Management Options
The fatigue from aripiprazole often improves with continued treatment as your body adjusts over 2-4 weeks. However, if it persists or worsens:
- Consider dose adjustment: Lower aripiprazole doses (2mg) may provide benefit with less sedation
- Timing matters: Taking aripiprazole at bedtime rather than morning may help
- Monitor for other sedating effects: Watch for excessive somnolence or lethargy that impairs function
Important Caveat
About 63% of patients on antidepressants experience at least one adverse effect, with fatigue being among the most common 4. The combination of medications may have additive sedating effects, though aripiprazole is clearly the more sedating agent in this scenario.
If fatigue becomes intolerable or affects your quality of life significantly, discuss with your prescriber whether the aripiprazole dose should be reduced or whether the medication should be continued at all, as tolerability must be balanced against therapeutic benefit.