From the Guidelines
Atomoxetine is associated with several side effects, including nausea, vomiting, fatigue, decreased appetite, abdominal pain, and somnolence, which are the most common adverse effects in children and adolescents, as reported in a 2022 study 1.
Common Side Effects
The most frequent side effects of atomoxetine include:
- Decreased appetite
- Nausea
- Vomiting
- Fatigue
- Abdominal pain
- Somnolence These side effects are often seen in children and adolescents, and it is essential to monitor patients closely, especially during the first few months of treatment or at times of dose change 1.
Serious Side Effects
More serious but less common side effects of atomoxetine include:
- Suicidal thoughts or behaviors, particularly in children and adolescents, which has led to special warnings by federal agencies and regulatory bodies 1
- Liver problems, indicated by yellowing of skin or eyes, dark urine, or abdominal pain
- Severe allergic reactions
- Urinary retention
- Priapism in children, adolescents, and adults
Cardiovascular Effects
Atomoxetine can also cause increased heart rate and blood pressure, which is why monitoring cardiovascular parameters is crucial, especially at the start of treatment 1. However, the risk of serious cardiovascular events is extremely low, as reported in a 2019 study 1.
Management of Side Effects
To minimize side effects, patients should start at a lower dose (typically 40mg daily for adults or 0.5mg/kg for children) and gradually increase to therapeutic levels, and should report any concerning symptoms to their healthcare provider immediately 1. It is also essential to monitor patients closely for suicidality, clinical worsening, and unusual changes of behavior, especially during the first few months of treatment or at times of dose change 1.
From the FDA Drug Label
Atomoxetine hydrochloride was administered to 5382 children or adolescent patients with ADHD and 1007 adults with ADHD in clinical studies. During the ADHD clinical trials, 1625 children and adolescent patients were treated for longer than 1 year and 2529 children and adolescent patients were treated for over 6 months The most commonly observed adverse reactions in patients treated with atomoxetine hydrochloride (incidence of 5% or greater and at least twice the incidence in placebo patients, for either BID or QD dosing) were: nausea, vomiting, fatigue, decreased appetite, abdominal pain, and somnolence Table 2: Common Treatment-Emergent Adverse Reactions Associated with the Use of Atomoxetine Hydrochloride in Acute (up to 18 weeks) Child and Adolescent Trials Adverse Reactiona Percentage of Patients Reporting Reaction Atomoxetine Hydrochloride (N=1597)Placebo(N=934) Gastrointestinal Disorders Abdominal painb1810 Vomiting 116 Nausea105 General Disorders and Administration Site Conditions Fatigue83 Irritability63 The following reactions did not meet this criterion but were reported by more atomoxetine-treated patients than placebo-treated patients and are possibly related to atomoxetine treatment: blood pressure increased, early morning awakening (terminal insomnia), flushing, mydriasis, sinus tachycardia, asthenia, palpitations, mood swings, constipation and dyspepsia
The side effects of atomoxetine include:
- Gastrointestinal disorders:
- Abdominal pain
- Vomiting
- Nausea
- General disorders:
- Fatigue
- Irritability
- Other reactions:
- Blood pressure increased
- Early morning awakening
- Flushing
- Mydriasis
- Sinus tachycardia
- Asthenia
- Palpitations
- Mood swings
- Constipation
- Dyspepsia 2
From the Research
Side Effects of Atomoxetine
- Common adverse events in children and adolescents include:
- Headache
- Abdominal pain
- Decreased appetite
- Vomiting
- Somnolence
- Nausea 3
- In adults, common adverse events include:
- Atomoxetine may also be associated with:
- Increased risk of non-serious adverse effects like nausea and vomiting, decreased sleep, and decreased appetite in children with autism spectrum disorder and attention deficit hyperactivity disorder 6
- Serious liver injury, with postmarketing data showing three patients having liver-related adverse events deemed probably related to atomoxetine treatment 3
- Suicidal ideation, with a black-box warning published in the US prescribing information based on findings from a meta-analysis showing that atomoxetine is associated with a significantly higher incidence of suicidal ideation than placebo 3
Special Considerations
- Atomoxetine should be used with caution in patients who have hypertension or any significant cardiovascular disorder 4
- Patients with hepatic insufficiency show an increase in atomoxetine exposure 3
- CYP2D6 inhibitors, such as paroxetine, are associated with changes in atomoxetine pharmacokinetics similar to those observed among poor CYP2D6 metabolizers 3