Rexulti Side Effects: What to Expect as a Depression Add-On

Your antidepressant helped, but not enough, and your prescriber suggested adding Rexulti. Then you read the list of possible side effects and started wondering which ones actually happen. That’s a reasonable question, and the answer depends a lot on the dose and on the two side effects that show up most in the trials.

Your brain’s dopamine and serotonin systems both help regulate mood, motivation, and movement. According to the Rexulti prescribing information, brexpiprazole partly activates dopamine D2 and serotonin 5-HT1A receptors while blocking serotonin 5-HT2A receptors. Compared with aripiprazole (Abilify), a clinical review of brexpiprazole notes it’s more potent at 5-HT1A and has less intrinsic activity at D2. That precision in how it touches the dopamine system is central to understanding its side effects, especially restlessness.

Aripiprazole (Abilify), Rexulti’s closest relative, is the usual point of comparison. Its label draws on more than 13,000 adults in clinical trials, and in its add-on depression trials, adults gained an average of 1.7 kg, while 25% experienced akathisia compared with 4% on placebo. The results are real, and the science is well established.

But Abilify’s profile no longer defines the whole class, and at Siggy we’d rather show you a drug’s own numbers than assume every add-on behaves the same. This guide covers Rexulti’s most common side effects, how they change with dose, what weight gain looks like over a year, and how its akathisia and weight data compare with Abilify’s. It also explains the boxed warnings and when to call for help. The differences between these drugs come down to pharmacology.

What This Page Covers

• What Are the Most Common Rexulti Side Effects?
• Why Rexulti Side Effects Rise With Dose
• How Much Weight Do People Gain on Rexulti?
• Rexulti vs Abilify for Akathisia and Weight
• What Do Rexulti’s Boxed Warnings Mean?
• When to Call Your Prescriber or 911

What Are the Most Common Rexulti Side Effects?

Rexulti is FDA-approved as an add-on to antidepressants for major depressive disorder in adults, and also for schizophrenia and agitation associated with Alzheimer’s dementia. In two 6-week trials of adults with depression, the side effects that stood out compared with placebo were:

• Akathisia: 9% versus 2%
• Weight increase: 7% versus 2%
• Headache: 7% versus 6%
• Somnolence (sleepiness): 5% versus 0.5%
• Tremor: 4% versus 2%
• Restlessness: 3% versus 0%
• Anxiety: 3% versus 1%
• Dizziness: 3% versus 1%

Only 3% of people on Rexulti stopped because of side effects, compared with 1% on placebo. Movement-related side effects other than akathisia, like stiffness or tremor, occurred in 6% versus 3%.

Akathisia is an inner, driven restlessness that makes it hard to sit still. It can feel like anxiety getting worse, which is why it’s easy to miss. Our guide to Abilify side effects explains what akathisia feels like and how it’s typically managed.

Why Rexulti Side Effects Rise With Dose

The label notes that akathisia and restlessness increased as the dose went up. The label’s fixed-dose depression trials show that pattern clearly, alongside weight gain at each dose.

Daily Dose	Akathisia	Average Weight Change	Gained 7% or More
Placebo	2%	+0.3 kg	2%
1 mg	4%	+1.3 kg	5%
2 mg	7%	+1.6 kg	5%
3 mg	14%	+1.6 kg	2%

That dose curve is one reason the label starts adults at 0.5 or 1 mg and targets 2 mg. Starting low may matter, too. A 2024 network meta-analysis of Japanese trials found that the akathisia risk at 2 mg was lower when treatment began at 0.5 mg rather than 1 mg.

Timing also shapes what you feel. Rexulti has a long half-life of about 91 hours and takes 10 to 12 days to reach steady levels, so side effects can keep shifting for up to two weeks after any dose change. Our guide to Rexulti dosage walks through the standard schedule.

How Much Weight Do People Gain on Rexulti?

Weight gain is Rexulti’s other signature side effect, and it looks different in the short term than over a year.

In the 6-week depression trials, people gained an average of 1.3 to 1.6 kg, or about 3 to 3.5 pounds, versus 0.3 kg on placebo. In the label’s long-term, open-label depression studies, average gain reached 2.9 kg at 26 weeks and 3.1 kg at 52 weeks. Thirty percent of people gained at least 7% of their body weight, 4% lost at least 7%, and 4% stopped Rexulti because of weight gain. Those long-term studies had no placebo group, so some change may reflect factors other than the drug.

Metabolic changes can come with weight. In the short-term trials, blood sugar shifts were similar to placebo, but in the long-term studies, 9% of people with normal or borderline fasting glucose moved into the high range. Triglycerides rose from normal to high in 13% of people on 2 mg, compared with 6% on placebo. The label calls for checking weight, fasting glucose, and lipids before or soon after starting, and periodically after that.

Rexulti vs Abilify for Akathisia and Weight

This comparison is one of the main reasons people search for Rexulti’s side effects. The table below pulls each drug’s results from its own label’s 6-week add-on depression trials, using the Abilify prescribing information for the Abilify column.

Measure	Rexulti	Abilify
Akathisia	9% (2% placebo)	25% (4% placebo)
Average weight change	+1.3 to +1.6 kg	+1.7 kg
Gained 7% or more	2% to 5%	5.2%
Stopped for side effects	3% (1% placebo)	6% (2% placebo)

On paper, Rexulti’s akathisia rate is well below Abilify’s, while short-term weight gain is similar. An independent number-needed-to-harm analysis put Rexulti’s akathisia rate in depression trials at 8.6%, meaning about one extra case for every 15 people treated.

Both labels caution that side effect rates from separate trials can’t be directly compared, and the pooled evidence is less clear-cut. The 2024 network meta-analysis found no statistically significant differences between Rexulti and Abilify on akathisia, weight gain, or any other outcome it measured. A larger 2026 network meta-analysis of 22 trials ranked Abilify slightly ahead of Rexulti on both response and dropout, though their ranges overlapped.

So the fair summary is this: Rexulti may cause less restlessness than Abilify for some people, and the drugs look similar on weight. If you had akathisia on Abilify, that history is worth raising with your prescriber, since it’s one of the practical reasons Rexulti gets considered. Our guide to Vraylar side effects covers another add-on with a different akathisia profile.

What Do Rexulti’s Boxed Warnings Mean?

A boxed warning is the FDA’s strongest label warning. Rexulti has two.

The first covers older adults with dementia-related psychosis, who face an increased risk of death on antipsychotics. In the label’s pooled analysis of 17 trials, largely with other atypical antipsychotics, the death rate over about 10 weeks was about 4.5% on drug versus 2.6% on placebo. Rexulti is approved for agitation associated with Alzheimer’s dementia, but not for dementia-related psychosis without that agitation.

The second applies because Rexulti is used with antidepressants. In pooled antidepressant trials, suicidal thoughts and behaviors increased by 14 cases per 1,000 people under 18 and 5 per 1,000 ages 18 to 24, with no increase from 25 to 64 and fewer cases at 65 and older. The label calls for close monitoring of everyone, especially early in treatment and after dose changes.

The label also warns about less common risks, including compulsive urges to gamble, shop, eat, or have sex, involuntary movements called tardive dyskinesia, and a rare emergency called neuroleptic malignant syndrome.

When to Call Your Prescriber or 911

Call 911 for a high fever with muscle stiffness and confusion, fainting, a seizure, or trouble breathing. Call or text 988 for thoughts of suicide or self-harm. Contact your prescriber promptly for:

• Restlessness that makes it hard to sit still, especially after a dose increase
• New or intense urges to gamble, spend, eat, or have sex
• Involuntary movements of the face, lips, or tongue
• Extreme thirst, frequent urination, or unusual hunger
• Worsening depression, anxiety, or irritability

Don’t stop Rexulti or your antidepressant without talking to your prescriber first.

With Rexulti, the side effect most likely to show up early, restlessness, is also the one most easily mistaken for your depression or anxiety getting worse.

Rexulti’s side effects follow a readable pattern: restlessness that rises with dose, weight gain that builds over months, and metabolic changes worth checking with routine labs. Compared with Abilify, it may cause less akathisia, though the head-to-head evidence isn’t conclusive. For a wider look at next steps when depression doesn’t lift, see our guide to treatment-resistant depression options.

Ready to take control of your mental health? Start your anonymous intake with Siggy and get your plan reviewed by a licensed prescriber.

This article is for education only and isn’t a substitute for personal medical advice. Don’t start, change, or stop a medication without talking to your prescriber, except in an emergency described here. It was reviewed for clinical accuracy and reflects sources available as of September 2026.