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# **Atomoxetine**
## Overview
Atomoxetine is a selective norepinephrine reuptake inhibitor (SNRI) used for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD).
## Primary Indications
* Attention-Deficit/Hyperactivity Disorder (ADHD)
## Adult Dosing
* **Initiation:** Start with 40 mg once daily.
* **Maintenance:** Increase to 80 mg once daily after a minimum of 3 days.
* **Further Titration:** If needed, may increase to a maximum of 100 mg once daily after an additional 2-4 weeks.
## Pediatric Dosing
* **Children and Adolescents (6 years and older):**
* **Initiation:** Start with 0.5 mg/kg/day once daily.
* **Maintenance:** Increase to 1.2 mg/kg/day once daily after a minimum of 3 days. This dose can be given as a single morning dose or divided into a morning and evening dose.
* **Further Titration:** If needed, may increase to a maximum of 1.4 mg/kg/day or 100 mg total daily dose (whichever is less) after an additional 2-4 weeks.
## Dose Adjustments
* **Hepatic Impairment:**
* **Moderate Impairment (Child-Pugh Class B):** Reduce dose by 50%.
* **Severe Impairment (Child-Pugh Class C):** Reduce dose by 25%.
## Contraindications
* Use within 2 weeks of MAO inhibitor therapy.
* Concurrent use with thioridazine or within 14 days of discontinuing thioridazine.
* Hypersensitivity to atomoxetine or any of its components.
## Adverse Effects
* **Common:** Nausea, vomiting, abdominal pain, decreased appetite, fatigue, dizziness, insomnia, dry mouth, erectile dysfunction, urinary retention.
* **Serious:** Hepatotoxicity, suicidal ideation/behavior (especially in children and adolescents), cardiovascular effects (increased blood pressure and heart rate), psychiatric effects (aggression, agitation), urinary hesitancy.
## Key Drug Interactions
* **MAO Inhibitors:** Contraindicated. Risk of hypertensive crisis.
* **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine):** Can significantly increase atomoxetine exposure. Consider reducing atomoxetine dose.
* **CYP2D6 Substrates:** Atomoxetine may increase concentrations of drugs metabolized by CYP2D6.
* **Vasopressors:** Use with caution due to potential for additive pressor effects.
* **Thioridazine:** Contraindicated. Increased risk of QTc prolongation and arrhythmias.
## Monitoring
* **Therapeutic Response:** Monitor ADHD symptom improvement.
* **Adverse Effects:** Screen for suicidal ideation, psychiatric symptoms, hepatobiliary signs (jaundice, dark urine, elevated LFTs), cardiovascular changes (BP, HR), and urinary symptoms.
* **Hepatic Function:** Consider LFTs if symptoms of liver dysfunction arise.
## Clinical Pearls
* Full therapeutic effect may take several weeks.
* Administer as a single morning dose to minimize insomnia. If somnolence or nausea occurs, consider dividing the dose into morning and evening.
* May be taken with or without food.
* Advise patients to report any signs of liver problems immediately.
* Black box warning for suicidal ideation/behavior in children and adolescents.
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**Disclaimer:** This information is intended for clinical professionals. Always consult the most current prescribing information and relevant clinical guidelines before making treatment decisions.
