1. Clinical Overview
Atomoxetine is a selective norepinephrine reuptake inhibitor (SNRI) specifically approved for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD). It is a non-stimulant medication, making it a Schedule H drug in India but not a controlled substance under the Narcotic Drugs and Psychotropic Substances (NDPS) Act, unlike stimulant ADHD treatments. It works by increasing norepinephrine in the prefrontal cortex, improving attention, focus, and impulse control.
| Onset | Duration | Bioavailability |
|---|---|---|
| Therapeutic effects on core ADHD symptoms may take 1 to 4 weeks to become fully apparent, though some effects on hyperactivity/impulsivity may be seen earlier. | Provides 24-hour symptom control with once-daily dosing due to its long half-life. | Approximately 63% in extensive metabolizers (most of the population) and 94% in poor metabolizers of CYP2D6. |
2. Mechanism of Action
Atomoxetine is a potent and selective inhibitor of the presynaptic norepinephrine transporter (NET) in the prefrontal cortex. It does not significantly affect the dopamine transporter in the striatum (unlike stimulants) or have appreciable affinity for serotonergic, cholinergic, or histaminergic receptors.
3. Indications & Uses
- Attention-Deficit/Hyperactivity Disorder (ADHD) in children (age 6 years and above)
- Attention-Deficit/Hyperactivity Disorder (ADHD) in adolescents
- Attention-Deficit/Hyperactivity Disorder (ADHD) in adults
4. Dosage & Administration
Adult Dosage: Initial: 40 mg once daily. Increase after minimum of 3 days to target dose of 80 mg once daily. May increase to maximum of 100 mg/day after 2-4 weeks if needed. Can be given as single morning dose or divided into two doses (morning and late afternoon/early evening).
Administration: Can be taken with or without food. Swallow capsule whole; do not open, chew, or crush. If capsule is opened accidentally, avoid contact with powder and wash hands immediately as it can cause eye irritation. For once-daily dosing, take in the morning. For twice-daily dosing, take morning and late afternoon/early evening. Avoid evening dosing if it causes insomnia.
5. Side Effects
Common side effects may include:
- Nausea
- Dry mouth
- Decreased appetite
- Insomnia
- Dizziness
- Fatigue
- Constipation
- Abdominal pain
- Vomiting
- Dyspepsia
- Mood swings
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Monoamine Oxidase Inhibitors (MAOIs) - e.g., Phenelzine, Selegiline, Moclobemide | Risk of hypertensive crisis, hyperthermia, serotonin syndrome. Potentially fatal. | Contraindicated |
| Strong CYP2D6 Inhibitors - e.g., Paroxetine, Fluoxetine, Quinidine | Increases atomoxetine plasma levels to those seen in poor metabolizers. Requires dose reduction (e.g., to 50% of normal dose). | Major |
| Albuterol (Salbutamol) and other Beta-2 Agonists | Potentiates cardiovascular effects (increased heart rate, blood pressure). | Moderate |
| Pressor Agents (e.g., Dopamine, Dobutamine) | Potentiates pressor effects, risk of hypertension. | Moderate |
| Other drugs that increase BP/HR (e.g., Decongestants like Pseudoephedrine) | Additive increases in blood pressure and heart rate. | Moderate |
7. Patient Counselling
- Do take the medication exactly as prescribed by your doctor.
- Do swallow the capsule whole with water; do not open, chew, or crush it.
- Do inform all your doctors and dentists you are taking atomoxetine.
- Do keep all follow-up appointments for monitoring of blood pressure, heart rate, height, and weight.
- Don't stop taking the medicine suddenly without consulting your doctor.
- Don't take with MAO inhibitors or within 2 weeks of stopping them.
- Don't use alcohol while on this medication.
8. Toxicology & Storage
Overdose: Symptoms may include somnolence, agitation, hyperactivity, abnormal behavior, gastrointestinal symptoms (nausea, vomiting), tachycardia, hypertension, mydriasis (dilated pupils), dry mouth. Severe overdose may lead to seizures, QT prolongation, and serotonin syndrome.
Storage: Store at room temperature (15°C to 30°C). Protect from moisture and light. Keep in the original container, tightly closed. Keep out of reach and sight of children. Do not use after the expiry date printed on the pack.