Understanding Atomoxetine Side Effects

Atomoxetine (brand name Strattera) is a non-stimulant medication used to treat ADHD in adults and children age 6 and older. Like all medications, it comes with potential side effects — some are mild and go away on their own, while others need immediate medical attention.

This guide breaks down what to expect when you start Atomoxetine, what's normal, and what should prompt a call to your doctor.

What Is Atomoxetine?

Atomoxetine is a selective norepinephrine reuptake inhibitor (SNRI) that works by increasing norepinephrine levels in the brain. Unlike stimulant ADHD medications like Adderall or Ritalin, it's not a controlled substance and doesn't carry a risk of abuse. For a deeper look at how it works, see our guide on Atomoxetine's mechanism of action.

Because Atomoxetine takes 4 to 6 weeks to reach its full effect, side effects may appear before you notice the benefits. That's normal — but it's important to know which side effects are expected and which are red flags.

Common Side Effects

These side effects are the most frequently reported in clinical trials. Many of them improve or go away entirely within the first few weeks of treatment:

• Nausea — One of the most common side effects, especially when starting the medication. Taking Atomoxetine with food can help.
• Decreased appetite — Many people notice less hunger, particularly during the first few weeks. This can lead to weight loss in some patients.
• Dry mouth — Drinking water throughout the day and chewing sugar-free gum can help.
• Constipation — Increasing fiber and fluid intake usually helps.
• Insomnia or sleep difficulties — Taking your dose in the morning (rather than evening) may reduce sleep problems.
• Dizziness — Usually mild. Stand up slowly from sitting or lying positions.
• Fatigue — Some people feel tired, especially in the first week or two.
• Stomach upset or abdominal pain — Taking the medication with food can reduce this.
• Urinary hesitancy — Difficulty starting urination. Tell your doctor if this is bothersome.
• Increased heart rate — A slight increase in resting heart rate is common. Your doctor should monitor this.
• Sexual side effects — Including erectile dysfunction and decreased libido. These affect some adults and should be discussed with your provider.
• Mood swings or irritability — More common in children and adolescents.

Serious Side Effects

These side effects are less common but require prompt medical attention:

Suicidal Thoughts and Behaviors (Boxed Warning)

Atomoxetine carries an FDA boxed warning about an increased risk of suicidal thinking in children and adolescents. In clinical trials, about 4 in 1,000 children taking Atomoxetine experienced suicidal thoughts compared to none on placebo. No completed suicides occurred in the trials.

This risk is highest during the first few months of treatment or when doses change. Watch for signs of depression, unusual behavior changes, agitation, or talk of self-harm. If you notice any of these, contact your doctor immediately or call 988 (Suicide & Crisis Lifeline).

Liver Damage (Hepatotoxicity)

Rare but serious cases of liver injury have been reported. Call your doctor right away if you experience:

• Yellowing of the skin or eyes (jaundice)
• Dark-colored urine
• Upper right abdominal pain
• Unexplained flu-like symptoms
• Itching

Cardiovascular Effects

Atomoxetine can increase blood pressure and heart rate. In most people this is mild, but it can be dangerous for those with pre-existing heart conditions. Seek medical attention for:

• Chest pain
• Shortness of breath
• Fainting
• Rapid or irregular heartbeat

Severe Allergic Reactions

Rarely, Atomoxetine can cause angioedema (swelling of the face, lips, tongue, or throat) or severe hives. This requires emergency medical care.

Other Serious Side Effects

• Psychotic or manic symptoms — Hallucinations, delusions, or mania, especially in patients without a prior history
• Aggressive behavior or hostility — More common in children
• Priapism — A painful erection lasting more than 4 hours. Seek emergency care immediately.
• Raynaud's phenomenon — Numbness, pain, or color changes in fingers or toes
• Seizures — Rare but reported

Side Effects in Specific Populations

Children and Adolescents

Children may be more likely to experience decreased appetite, weight loss, stomach pain, mood changes, and irritability. The suicidal ideation risk highlighted in the boxed warning is specific to this age group. Growth should be monitored regularly.

CYP2D6 Poor Metabolizers

About 7% of Caucasians are "poor metabolizers" of Atomoxetine, meaning their bodies break down the drug more slowly. These individuals may experience stronger side effects at standard doses. If side effects seem unusually severe, ask your doctor about CYP2D6 testing.

Patients with Liver Problems

People with hepatic impairment need lower doses of Atomoxetine because the drug is processed by the liver. Your doctor should adjust your dose accordingly.

Pregnancy

Atomoxetine is classified as Category C for pregnancy — it should only be used if the potential benefit justifies the potential risk to the fetus. Discuss this with your doctor if you're pregnant or planning to become pregnant.

How to Manage Common Side Effects

Most side effects are manageable with simple adjustments:

1. Take it with food — This reduces nausea and stomach upset significantly.
2. Time your dose right — Take it in the morning to minimize sleep problems. If your doctor prescribes twice-daily dosing, take the second dose in the early afternoon.
3. Stay hydrated — Helps with dry mouth, constipation, and dizziness.
4. Eat regular meals — Even if your appetite is reduced, try to eat balanced meals at scheduled times.
5. Give it time — Many side effects improve after the first 2 to 4 weeks as your body adjusts.
6. Talk to your doctor — If side effects are bothersome, your doctor may adjust your dose or suggest strategies to help.

Don't stop taking Atomoxetine suddenly without talking to your doctor. While it's not addictive, abrupt discontinuation should be managed by your provider.

Final Thoughts

Atomoxetine is generally well-tolerated, especially compared to stimulant ADHD medications. Most side effects are mild and improve with time. The serious side effects — particularly the suicidal ideation warning in young patients and the risk of liver damage — are rare but important to know about.

The key is communication with your doctor. Report any side effects that concern you, especially in the first few months of treatment. And remember that Atomoxetine takes 4 to 6 weeks to reach full effect, so give it time before making a judgment.

For more about this medication, read our complete overview: What Is Atomoxetine? Uses, Dosage, and What You Need to Know. If you need help finding Atomoxetine at a pharmacy near you, Medfinder can help you locate it in stock.