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# **ATTOMOXETINE** ## Overview Atomoxetine is a selective norepinephrine reuptake inhibitor (SNRI) used for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD). It is a non-stimulant medication. ## Primary Indications * Treatment of Attention-Deficit/Hyperactivity Disorder (ADHD) in pediatric, adolescent, and adult patients. ## Adult Dosing * **Initiation:** Start at 40 mg once daily. * **Titration:** After a minimum of 3 days, increase to a target dose of 80 mg once daily, given either once daily or divided into two doses (morning and evening). * **Maximum:** The maximum recommended daily dose is 100 mg. ## Pediatric Dosing (6 years and older) * **Initiation:** Start at 0.5 mg/kg/day once daily. * **Titration:** After a minimum of 3 days, increase to a target dose of 1.2 mg/kg/day, given either once daily or divided into two doses (morning and evening). * **Maximum:** * Children under 70 kg: The maximum recommended daily dose is 1.4 mg/kg/day or 100 mg, whichever is less. * Children 70 kg and over: The maximum recommended daily dose is 100 mg. ## Dose Adjustments * **Hepatic Impairment:** * **Moderate impairment (Child-Pugh Class B):** Reduce the starting dose by 50% and reduce the maximum recommended daily dose by 25%. * **Severe impairment (Child-Pugh Class C):** Reduce the starting dose by 75% and reduce the maximum recommended daily dose by 50%. * **CYP2D6 Poor Metabolizers:** Patients who are CYP2D6 poor metabolizers may experience higher atomoxetine concentrations. Dose should be initiated and titrated cautiously. If side effects are bothersome, consider reducing the dose. ## Contraindications * Use within 14 days of the previous day's use of a monoamine oxidase inhibitor (MAOI) or within 14 days of stopping an MAOI. * Known hypersensitivity to atomoxetine or any of its ingredients. * Concurrent use with certain antipsychotics or other drugs that prolong the QT interval. ## Adverse Effects * **Common:** Dry mouth, nausea, decreased appetite, abdominal pain, vomiting, fatigue, dizziness, insomnia, somnolence, increased heart rate, increased blood pressure, urinary hesitation. * **Serious:** * Hepatotoxicity (rare) * Suicidal thoughts and behaviors (especially in children and adolescents) * Cardiovascular effects (increased heart rate and blood pressure) * Urologic symptoms (urinary retention) * Priapism (rare) * Aggression and agitation * Growth suppression (in children and adolescents) ## Key Drug Interactions * **MAOIs:** Contraindicated due to risk of hypertensive crisis. * **CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine, quinidine):** May increase atomoxetine concentrations, requiring dose reduction in poor metabolizers or patients taking strong CYP2D6 inhibitors. * **CYP2D6 Substrates:** Atomoxetine is a moderate inhibitor of CYP2D6. May increase concentrations of drugs metabolized by CYP2D6 (e.g., some antidepressants, antipsychotics, beta-blockers). * **Sympathomimetic Agents (e.g., stimulants, decongestants):** Use with caution due to potential additive effects on blood pressure and heart rate. * **Drugs that prolong the QT interval:** Use with caution due to increased risk of arrhythmias. ## Monitoring * **Mental Health:** Monitor for suicidal thoughts and behaviors, aggression, and agitation, especially during initiation and dose changes. * **Cardiovascular:** Monitor blood pressure and heart rate at baseline and periodically during treatment. * **Hepatic Function:** Monitor for signs and symptoms of liver injury (e.g., jaundice, dark urine, pruritus, abdominal pain) and consider baseline and periodic liver function tests. * **Growth:** Monitor growth (height and weight) in pediatric and adolescent patients. * **Urologic:** Monitor for urinary hesitation or retention. ## Clinical Pearls * Atomoxetine is not a stimulant and does not have abuse potential. * It may take several weeks (up to 2-4 weeks) for the full therapeutic effect to be observed. * Do not crush or chew capsules; administer whole. If unable to swallow capsules, they can be opened and contents sprinkled on applesauce. Do not inhale powder from opened capsules. * Discontinuation should be gradual, especially if patient has been on therapy for a long time, to avoid withdrawal symptoms, although this is less established than with stimulants. *** **Disclaimer:** This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the most current prescribing information and professional resources for complete details and to verify dosing and safety recommendations before making any treatment decisions.