Simtriyo Side Effects: What to Expect and How to Manage Them

Written by Beth Johnston, BCPS, PharmD
Medically Reviewed by Patricia Weiser, PharmD on August 21, 2026

Simtriyo (centanafadine) is used for attention deficit hyperactivity disorder (ADHD).

Like most medicines, Simtriyo may cause side effects — some more common than others. Some Simtriyo side effects may improve as your body adjusts to treatment.

Keep reading to learn about possible side effects of Simtriyo, what you can do to prevent them, what to do if they happen, and when to tell your health care provider.

This article does not include all possible side effects of Simtriyo. Tell your health care provider if you have side effects that are ongoing or bother you, even if they are not listed.

The most common side effects reported in clinical studies include the following and may vary by age:

  • Decreased appetite
  • Headache
  • Dry mouth
  • Nausea
  • Diarrhea
  • Rash
  • Trouble sleeping

In most cases, these side effects are temporary and often improve on their own. Do not stop taking Simtriyo unless your provider recommends it.

Serious Simtriyo side effects are less common but may include:

If you think you may be having a serious side effect, contact your health care provider right away. In some cases, severe symptoms may require urgent medical care. Your provider can look at your symptoms and explain what steps to take next.

Some Simtriyo side effects can be managed at home, while others need medical treatment. Your health care provider may pause or stop treatment depending on the type and severity of your symptoms.

The following sections will take a closer look at some possible side effects of Simtriyo and tips to help prevent or manage them.

1. Suicidal thoughts or actions

Some people who take Simtriyo, especially children aged 6-12 years, may have suicidal thoughts. This seems more likely to happen within the first few months of taking Simtriyo.

Symptoms or warning signs may include:

  • New or increased thoughts of suicide or death
  • New or increased feelings of anxiety, depression, or other unusual changes in mood or behavior
  • Suicide attempt

If you or your child are having thoughts of harming yourself or suicide, call 911 or call or text 988, the Suicide & Crisis Lifeline.

Also, tell your health care provider if this happens. They may suggest other treatments or decide to stop Simtriyo.

2. Low appetite

You may notice a decline in appetite when you take Simtriyo. This side effect seems common among all ages.

Symptoms may include:

  • Not feeling hungry
  • Less interest in food
  • Eating less than usual
  • Weight loss

It is important to try to eat well even if your ADHD medication lowers your appetite. Eating well can help you maintain your weight, energy, and overall nutrition.

The following tips may help if appetite is low:

  • Eat small meals more frequently.
  • Keep easy-to-eat snacks nearby.
  • Try nutritional shakes or smoothies if solid foods are hard to eat.
  • Some people also tolerate cold foods or soft foods better when appetite is low.
  • Eat your favorite foods.
  • Choose nutrient-dense foods to make sure you are getting enough protein, calories, vitamins, and minerals to support overall health.

If these tips do not seem to be enough, ask your health care provider or talk to a dietitian about other ways to make sure you are eating well.

3. Nausea

Nausea is a common side effect of Simtriyo. Nausea seems more common among teens and adults.

Nausea is the feeling that you might throw up, but it doesn’t always lead to vomiting.

Tips to help prevent or ease nausea:

  • Plan smaller, more frequent meals (instead of two or three large ones) and stop eating as soon as you feel full.
  • Avoid high-fat foods, such as cheese, butter, and greasy foods
  • Choose bland foods, such as saltine crackers, rice, or toast.
  • Sip on clear liquids throughout the day to avoid dehydration.
  • Try popsicles, Jell-O, ginger or peppermint tea, or even acupressure wristbands.

Let your health care provider know if nausea is severe, doesn’t go away, or makes it hard for you to eat and drink enough. Your health care provider can recommend ways to treat your nausea; if nausea makes you unable to tolerate the medicine, they may switch you to a different medicine for ADHD.

4. Trouble sleeping

Trouble sleeping (insomnia) is a common side effect of Simtriyo in adults, but it can also happen in children. Possible symptoms include trouble falling asleep, staying asleep, or waking up too early. 

Here are some tips to lower your risk of having insomnia when taking Simtriyo:

  • Try to go to bed and get up around the same time each day.
  • Keep the room temperature set at a comfortable temperature for sleeping.
  • Make sure your room is dark and quiet.
  • Do not drink alcohol or caffeine close to bedtime.
  • Get regular exercise, but avoid exercising within five hours of your normal bedtime.
  • Try to avoid napping, especially in the afternoon.

If you are having trouble sleeping that is not going away or interfering with your daily activities, talk to your health care provider. They may change your medicine or recommend other ways to improve your sleep.

Yes. There is a risk of slowed growth in children, especially children between 6 and 12 years old. Children should have their height and weight checked often during treatment with Simtriyo. Keep all of these appointments so your child’s health care provider can monitor their growth over time. Treatment with Simtriyo may be stopped if your child is not growing or gaining weight as expected.

You can lower your risk of side effects by:

  • Taking Simtriyo exactly as prescribed at around the same time daily
  • Avoiding alcoholic drinks when you take Simtriyo and for at least two hours after taking your dose
  • Keeping track of any new or changing symptoms and sharing them with your health care provider
  • Telling your health care provider about side effects that do not improve or start to interfere with daily activities

Your health care provider can help you decide whether changes to your treatment plan are needed.

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