Atomoxetine (Strattera) Side Effects: What to Expect and When to Call Your Doctor

Atomoxetine — the generic form of the now-discontinued brand Strattera — is generally well tolerated, but like all medications it comes with side effects. Understanding what to expect, when side effects typically occur, and when to contact your doctor will help you or your child get through the adjustment period successfully.

Boxed Warning: What You Must Know Before Starting

Atomoxetine carries the FDA's most serious warning — a black box warning — for increased risk of suicidal ideation in children and adolescents. Clinical trials showed suicidal thoughts occurred in 0.4% of children and adolescents on atomoxetine versus 0% in those on placebo. This risk is most significant in the first few months of treatment and when doses are changed.

If your child (or you) is starting atomoxetine, watch closely for new or worsening depression, irritability, agitation, anxiety, unusual behavior changes, or any talk of self-harm. Contact your doctor immediately if any of these occur.

Common Side Effects: What Most People Experience

The most common side effects of atomoxetine occur most often during the first few weeks of treatment, particularly as the dose is being increased. Many resolve on their own as your body adjusts. These include:

Decreased appetite: One of the most common complaints, especially in children. Taking atomoxetine with food can help.

Nausea and stomach upset: Very common, especially early on. Taking with food usually reduces nausea.

Fatigue and drowsiness: Some people feel tired, especially in the first 2–4 weeks. Taking a once-daily dose at bedtime (off-label) may help with daytime drowsiness.

Dizziness: Particularly when standing up quickly (orthostatic hypotension). Rise slowly from seated or lying positions.

Dry mouth: Staying hydrated and chewing sugar-free gum can help.

Headache: Common early in treatment. Usually improves with time.

Mood swings / irritability: Some patients experience emotional lability, particularly early in treatment.

Constipation: Increasing fiber and water intake can help manage this.

Urinary hesitation: Some patients notice difficulty starting urination; report this to your doctor if persistent.

Sexual side effects in adults: Decreased libido and difficulty with erection or ejaculation are reported in adult men.

Serious Side Effects: When to Call Your Doctor Immediately

The following side effects require prompt medical attention. Call your doctor right away or go to an emergency room if you experience any of these:

Liver problems: Yellowing of the skin or eyes (jaundice), dark urine, upper right abdominal pain, unexplained flu-like symptoms, or itching. Atomoxetine must be permanently discontinued if liver injury is confirmed.

Heart problems: Chest pain, shortness of breath, fainting, or rapid heartbeat. Atomoxetine increases heart rate and blood pressure slightly in most patients; in those with underlying heart conditions, this can be more significant.

Suicidal thoughts or behavior: Any thoughts of self-harm or suicide; call 988 (Suicide & Crisis Lifeline) or 911 immediately.

Psychosis or mania: Hallucinations, delusions, manic episodes, or unusual thought disturbances — especially in people without prior history.

Severe allergic reaction: Hives, swelling of face/lips/tongue/throat, difficulty breathing.

Priapism (painful prolonged erection): An erection lasting more than 4 hours is a medical emergency.

Side Effect Timing: When Do They Start and Stop?

Most common side effects (nausea, headache, decreased appetite) begin within the first week of treatment and typically improve over 2–4 weeks as the body adjusts. If they persist beyond a month or are severe, contact your prescriber — a dose adjustment or timing change often helps.

Tips to Minimize Common Side Effects

Take with food to reduce nausea and stomach upset

Stay well hydrated throughout the day

Rise slowly from bed or chairs to minimize dizziness

If appetite suppression is a problem in children, offer high-calorie healthy foods at breakfast (before the medication peaks) and at dinner

Don't split or crush the capsules — the powder inside can be irritating to eyes and skin

The Bottom Line

Most people tolerate atomoxetine well, especially after the first few weeks. Serious side effects are rare but require immediate attention. Understanding what to watch for helps you catch problems early and stick with treatment long enough to see results. Also check our guide on atomoxetine drug interactions to know what to avoid while on this medication.