Atomoxetine

For adults with ADHD, the standard starting dose of Atomoxetine is typically 40 mg once daily. This initial dose allows the body to acclimate to the medication and helps minimize gastrointestinal side effects. After a minimum of three days at this starting dose, healthcare providers usually increase the dosage to a target total daily dose of approximately 80 mg.

This target dose can be taken as a single dose in the morning or divided into two equal doses (morning and late afternoon/early evening) if side effects like nausea or insomnia occur. If the patient does not achieve an adequate clinical response after 2 to 4 weeks at 80 mg, the dose may be increased to a maximum of 100 mg daily. There is no clinical evidence that doses higher than 100 mg provide additional benefits, but they do significantly increase the risk of toxicity.

Atomoxetine is approved for children and adolescents weighing 70 kg (154 lbs) or less, and for those weighing more than 70 kg.

• Children and Adolescents (up to 70 kg): Dosing is weight-based. The starting dose is approximately 0.5 mg/kg per day. This dose should be maintained for at least three days before increasing to the target dose of approximately 1.2 mg/kg per day. The maximum daily dose in this population should not exceed 1.4 mg/kg or 100 mg, whichever is less.
• Children and Adolescents (over 70 kg): Dosing follows the adult protocol, starting at 40 mg daily and titrating up to a target of 80 mg daily, with a maximum of 100 mg.

Atomoxetine is not approved for use in children under the age of 6, as safety and efficacy have not been established in this age group.

Renal Impairment

Specific dosage adjustments are generally not required for patients with renal insufficiency, as the kidneys are not the primary route of metabolism for the parent drug. However, Atomoxetine may increase blood pressure, so patients with end-stage renal disease should be monitored closely.

Hepatic Impairment

For patients with moderate hepatic impairment (Child-Pugh Class B), the initial and target doses should be reduced to 50% of the normal dose. For those with severe hepatic impairment (Child-Pugh Class C), the dose should be reduced to 25% of the normal dose.

Elderly Patients

Clinical studies did not include sufficient numbers of subjects aged 65 and older to determine whether they respond differently than younger subjects. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range.

Atomoxetine should be swallowed whole. Do not open, crush, or chew the capsules. The powder inside the capsule is a known ocular irritant; if a capsule is accidentally broken and the powder comes into contact with the eyes, they should be flushed immediately with water and medical advice sought.

• With or Without Food: Atomoxetine can be taken regardless of meal timing. However, taking it with food (especially a protein-rich meal) can significantly reduce common side effects like nausea and stomach upset.
• Consistency: Take the medication at the same time(s) each day to maintain steady levels in the bloodstream.
• Storage: Store at room temperature (20°C to 25°C / 68°F to 77°F) in a dry place away from direct sunlight.

If you miss a dose, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and resume your regular schedule. Do not take two doses at once to make up for a missed one, as this increases the risk of adverse cardiovascular effects.

Signs of Atomoxetine overdose may include extreme drowsiness, agitation, hyperactivity, abnormal behavior, and gastrointestinal symptoms. More serious signs include tachycardia (rapid heart rate), hypertension (high blood pressure), and pupillary dilation (mydriasis). In some cases, seizures have been reported.

In the event of an overdose, contact a Poison Control Center (1-800-222-1222 in the US) or seek emergency medical attention immediately. Treatment is primarily supportive, focusing on maintaining an airway and monitoring cardiac and vital signs.

> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or stop the medication without medical guidance, as symptoms of ADHD may return.

Side effects of Atomoxetine often differ between pediatric and adult populations. In clinical trials, the most frequently reported adverse effects include:

• Gastrointestinal Distress: Nausea and vomiting are very common, particularly during the first few weeks of treatment. Patients often describe a 'heavy' or 'queasy' feeling in the stomach shortly after ingestion.
• Decreased Appetite: Many patients experience a significant reduction in hunger, which can lead to weight loss. In children, this requires close monitoring of growth curves.
• Dry Mouth (Xerostomia): A persistent feeling of dryness in the mouth and throat.
• Fatigue and Somnolence: Unlike stimulants, Atomoxetine can cause tiredness or daytime sleepiness in some patients, especially when first starting the drug.
• Increased Heart Rate and Blood Pressure: Most patients experience a modest increase in pulse (about 6 bpm) and blood pressure (about 2-3 mmHg).

• Insomnia: Difficulty falling or staying asleep, though this is less common than with stimulant medications.
• Dizziness: A feeling of lightheadedness, particularly when standing up quickly (orthostatic hypotension).
• Mood Swings: Irritability, tearfulness, or minor emotional lability.
• Urinary Hesitancy: In adults, Atomoxetine can cause difficulty starting urination or a weak stream due to its effects on the internal urethral sphincter (mediated by norepinephrine).
• Sexual Dysfunction: Adults may report erectile dysfunction, decreased libido, or ejaculatory delay/failure.

• Priapism: A rare but serious condition involving a painful, long-lasting erection (over 4 hours). This is a medical emergency.
• Syncope: Fainting spells, often related to cardiovascular changes.
• Severe Skin Reactions: Including angioedema (swelling under the skin) and urticaria (hives).
• Raynaud's Phenomenon: Reduced blood flow to the fingers and toes, causing them to feel cold or turn blue/white.

> Warning: Stop taking Atomoxetine and call your doctor immediately if you experience any of these serious symptoms.

1. 1Suicidal Ideation: Especially in children and adolescents, watch for new or worsening thoughts of self-harm, deep depression, or unusual changes in behavior.
2. 2Hepatotoxicity (Liver Injury): Symptoms include jaundice (yellowing of the skin or eyes), dark urine, pain in the upper right abdomen, and unexplained flu-like symptoms. Atomoxetine can cause severe liver damage in rare cases.
3. 3Cardiovascular Events: Chest pain, shortness of breath, or palpitations. Patients with pre-existing heart conditions are at higher risk for sudden death or myocardial infarction (heart attack).
4. 4Psychotic or Manic Symptoms: New-onset hallucinations (hearing or seeing things that aren't there), delusions, or extreme mania in patients without a prior history of such issues.
5. 5Severe Allergic Reaction: Difficulty breathing, swelling of the face or throat, or a widespread blistering rash.

• Growth Suppression: Long-term use in children has been associated with a temporary slowing of growth (both height and weight). Most children eventually reach their predicted adult height, but healthcare providers should monitor growth parameters regularly.
• Cardiovascular Strain: Because Atomoxetine chronically elevates heart rate and blood pressure, the long-term impact on the cardiovascular system requires ongoing monitoring, particularly in patients with borderline hypertension.

Suicidal Ideation in Children and Adolescents: The FDA has issued a Black Box Warning for Atomoxetine regarding an increased risk of suicidal thinking and behavior in children and adolescents. In short-term studies, the risk was approximately 0.4% in patients taking Atomoxetine compared to 0% in the placebo group. No suicides occurred in these trials, but the risk of ideation is significant. Patients started on therapy must be observed closely for clinical worsening, suicidality, or unusual changes in behavior. This monitoring is most critical during the first few months of therapy or during dose adjustments.

Report any unusual symptoms or persistent side effects to your healthcare provider. Many side effects, particularly gastrointestinal ones, may diminish over time as your body adjusts to the medication.

Atomoxetine is a potent medication that affects the central nervous system and cardiovascular system. It is not a controlled substance, but it must be used under strict medical supervision. Patients should be screened for cardiovascular disease and psychiatric disorders before beginning treatment.

Suicidality in Children and Adolescents: Atomoxetine increased the risk of suicidal ideation (thoughts of suicide) in short-term studies of children and adolescents with ADHD. Anyone considering the use of Atomoxetine in a child or adolescent must balance this risk with the clinical need. Families and caregivers must be alerted to the need for daily observation and communication with the prescriber. Symptoms such as anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania, and mania have been reported in pediatric patients being treated with antidepressants and medications like Atomoxetine.

• Hepatotoxicity (Liver Risk): Post-marketing reports indicate that Atomoxetine can cause severe liver injury. In some cases, this has progressed to liver failure requiring a transplant. Patients should be instructed to contact their doctor immediately if they develop signs of liver dysfunction (e.g., pruritus, dark urine, jaundice, right upper quadrant tenderness, or unexplained 'flu-like' symptoms). The drug should be discontinued and not restarted in patients with evidence of liver injury.
• Cardiovascular Risks: Atomoxetine can increase blood pressure and heart rate. It should be used with extreme caution in patients with hypertension, tachycardia, or cardiovascular or cerebrovascular disease. Pre-existing structural cardiac abnormalities, cardiomyopathy, and serious heart rhythm abnormalities increase the risk of sudden death.
• Psychiatric Effects: Treatment-emergent psychotic or manic symptoms (e.g., hallucinations, delusional thinking, or mania) in children and adolescents without a prior history can be caused by Atomoxetine at normal doses.
• Aggressive Behavior: ADHD is often associated with hostility and aggression; however, these symptoms were also observed in clinical trials. Patients should be monitored for the appearance or worsening of aggressive behavior.
• Urinary Retention: In adults, the medication may cause urinary tract obstruction and retention. If symptoms of bladder outlet obstruction occur, consult a physician.

Healthcare providers typically perform the following monitoring:

1. 1Baseline Cardiac Screen: Blood pressure and heart rate measurement; physical exam for heart disease.
2. 2Growth Monitoring: Height and weight should be tracked in pediatric patients at least every 6 months.
3. 3Liver Function: While routine blood tests aren't always required, any sign of liver distress warrants immediate liver function tests (LFTs).
4. 4Mental Status: Regular screening for mood changes, anxiety, or suicidal thoughts.

Atomoxetine may cause dizziness or somnolence (drowsiness) in some patients. Until you know how this medication affects you, use caution when driving a car, operating heavy machinery, or performing hazardous tasks.

While there is no direct chemical interaction between Atomoxetine and alcohol, alcohol can worsen certain side effects like dizziness, drowsiness, and impaired judgment. Additionally, alcohol can affect mood and impulse control, which may counteract the benefits of ADHD treatment. It is generally advised to avoid or strictly limit alcohol consumption while taking Atomoxetine.

Unlike stimulants, Atomoxetine does not typically require a slow taper to avoid withdrawal symptoms. However, ADHD symptoms will likely return once the medication is stopped. Always consult your doctor before stopping the medication to ensure a safe transition.

> Important: Discuss all your medical conditions, especially heart problems or mental health history, with your healthcare provider before starting Atomoxetine.

• Monoamine Oxidase Inhibitors (MAOIs): Atomoxetine should not be taken with an MAOI (e.g., phenelzine, selegiline, tranylcypromine) or within 14 days of discontinuing an MAOI. Simultaneous use can cause a 'hypertensive crisis,' a life-threatening spike in blood pressure, as well as hyperthermia (dangerously high body temperature) and severe muscle rigidity.

• CYP2D6 Inhibitors: Because Atomoxetine is metabolized by the CYP2D6 enzyme, drugs that inhibit this enzyme can dramatically increase Atomoxetine levels. Common inhibitors include Fluoxetine (Prozac), Paroxetine (Paxil), and Quinidine. In patients taking these drugs, the Atomoxetine dose may need to be reduced significantly (e.g., starting at 40 mg and not increasing unless clinically necessary).
• Antihypertensive Agents: Atomoxetine may decrease the effectiveness of medications used to treat high blood pressure. Close monitoring of blood pressure is required.
• Pressor Agents: Drugs that also increase blood pressure (e.g., dopamine, dobutamine) should be used cautiously. There is a risk of additive effects on blood pressure.

• Albuterol (and other Beta-2 Agonists): Atomoxetine can potentiate the cardiovascular effects of albuterol (increased heart rate and blood pressure). This is particularly important for patients using nebulized albuterol or high-dose inhalers for asthma.
• Tricyclic Antidepressants (TCAs): Combining Atomoxetine with TCAs (like imipramine or amitriptyline) can increase the risk of cardiovascular side effects due to additive effects on norepinephrine reuptake.

• High-Fat Meals: While food does not stop the absorption of Atomoxetine, a high-fat meal can delay the time it takes to reach peak concentration (Tmax) by about 3 hours. This is usually not clinically significant but can be used to manage the 'peak' side effects.
• Caffeine: High intake of caffeine (coffee, energy drinks) may exacerbate the heart rate and blood pressure increases caused by Atomoxetine, leading to jitters, anxiety, or palpitations.

• St. John's Wort: May affect the metabolism of many drugs and could theoretically interact with the serotonergic or noradrenergic systems, although data specific to Atomoxetine is limited.
• Melatonin: Often used by ADHD patients for sleep; while generally safe, it may increase daytime drowsiness if combined with the sedative effects some experience with Atomoxetine.
• Stimulant Supplements: Avoid 'fat burners' or pre-workout supplements containing synephrine, ephedra, or high caffeine, as these can cause dangerous increases in heart rate when combined with Atomoxetine.

Atomoxetine is not known to interfere with most standard laboratory tests. However, it does not show up on standard 'amphetamine' drug screens because it is chemically distinct from stimulants. If you are undergoing a workplace drug test, you should still disclose your prescription to the testing facility.

Mechanism of Interaction Summary

| Interaction Type | Mechanism | Clinical Consequence |

|---|---|---|

| CYP2D6 Inhibition | Reduced clearance of Atomoxetine | Increased toxicity, higher side effect profile |

| Pharmacodynamic | Additive noradrenergic activity | Hypertensive crisis, tachycardia |

| Absorption | Gastric emptying delay (Food) | Delayed onset, reduced GI irritation |

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including over-the-counter cold medicines which may contain decongestants that increase blood pressure.

Atomoxetine is strictly contraindicated in the following scenarios:

1. 1MAOI Use: As noted, use within 14 days of a Monoamine Oxidase Inhibitor is forbidden due to the risk of fatal hypertensive crisis.
2. 2Narrow-Angle Glaucoma: Atomoxetine was associated with an increased risk of mydriasis (pupil dilation) in clinical trials. In patients with narrow-angle glaucoma, this can trigger an acute attack of angle-closure glaucoma, which is a medical emergency that can lead to permanent vision loss.
3. 3Pheochromocytoma: Patients with a history of pheochromocytoma (a rare tumor of the adrenal gland) or a history of such tumors should not take Atomoxetine. The drug can cause serious cardiovascular reactions and blood pressure spikes in these patients due to the release of catecholamines.
4. 4Severe Cardiovascular Disorders: Patients with advanced arteriosclerosis, symptomatic heart disease, or moderate to severe hypertension should avoid this medication as it can exacerbate these conditions.

These conditions require a careful risk-benefit analysis by a specialist:

• Pre-existing Psychosis or Bipolar Disorder: Atomoxetine may induce mania or worsen psychotic symptoms. Patients should be screened for bipolar disorder before starting ADHD treatment to avoid 'switching' the patient into a manic episode.
• Moderate Hypertension: Since Atomoxetine increases BP, patients with existing high blood pressure must be stabilized on antihypertensives before starting and monitored weekly.
• Urinary Retention History: Those with prostatic hypertrophy (enlarged prostate) may find that Atomoxetine makes urination significantly more difficult.

Patients who have demonstrated hypersensitivity (severe allergy) to Atomoxetine or any of the inactive ingredients in the capsule (such as starch or gelatin) must not take the medication. There is no known cross-sensitivity with stimulant medications (like Adderall or Ritalin), making Atomoxetine a safe alternative for those allergic to stimulants.

> Important: Your healthcare provider will evaluate your complete medical history, including heart health and eye health, before prescribing Atomoxetine.

Atomoxetine is classified as Pregnancy Category C (under the older FDA system). There are no adequate and well-controlled studies in pregnant women. Animal studies have shown some evidence of fetal toxicity at high doses. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

• First Trimester: Data is limited; however, the risk of untreated ADHD (impulsivity, accidents) must be weighed against the unknown risk of the drug.
• Registry: Pregnant women taking Atomoxetine are encouraged to enroll in the National Pregnancy Registry for Psychiatric Medications to help gather more data.

It is not known whether Atomoxetine or its metabolites are excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when Atomoxetine is administered to a nursing woman. The decision to breastfeed while taking Atomoxetine should be made in consultation with a pediatrician, considering the importance of the drug to the mother.

Atomoxetine is approved for ADHD in children aged 6 years and older.

• Effectiveness: Clinical trials show it is effective for both inattentive and hyperactive symptoms.
• Growth: As mentioned, weight and height must be monitored. If a child is not growing or gaining weight as expected, the healthcare provider may consider a 'drug holiday' or a dose reduction.
• Safety: The primary concern in this population is the Black Box Warning regarding suicidal ideation.

There is very limited data on the use of Atomoxetine in patients over 65. Because elderly patients are more likely to have decreased hepatic, renal, or cardiac function, and are more likely to be taking multiple medications (polypharmacy), they should be started on the lowest possible dose. Blood pressure and heart rate must be monitored closely due to the higher baseline risk of cardiovascular events in this age group.

In subjects with end-stage renal disease, Atomoxetine exposure was higher than in healthy subjects, but the difference was not considered clinically significant for those with mild to moderate impairment. No specific starting dose adjustment is required, but titration should be done slowly and with careful monitoring of blood pressure.

Hepatic impairment significantly increases Atomoxetine exposure.

• Moderate (Child-Pugh B): Start at 50% of the normal dose.
• Severe (Child-Pugh C): Start at 25% of the normal dose.

Failure to adjust the dose in these patients can lead to toxic accumulation of the drug.

> Important: Special populations require individualized medical assessment and more frequent follow-up appointments.

Atomoxetine is a highly selective inhibitor of the pre-synaptic norepinephrine transporter (NET). Its chemical structure is (R)-N-methyl-3-(2-methylphenoxy)-3-phenylpropylamine hydrochloride. It has a high affinity for the NET but low affinity for the serotonin (SERT) or dopamine (DAT) transporters. By blocking the NET, it prevents the reuptake of norepinephrine, thereby increasing the synaptic concentration of this neurotransmitter. In the prefrontal cortex, where dopamine transporters are scarce, Atomoxetine also results in increased dopamine levels because norepinephrine transporters can take up dopamine. Importantly, it does not affect dopamine in the striatum or nucleus accumbens, which explains its lack of abuse potential.

Atomoxetine does not act as a stimulant in the traditional sense. It does not cause a rapid increase in synaptic monoamines. Instead, its clinical effects develop over 2 to 4 weeks. It does not show a 'crash' or 'rebound' effect as the dose wears off, providing a smoother 24-hour symptom control compared to short-acting stimulants. It has minimal affinity for histaminergic, cholinergic, or alpha-adrenergic receptors, which limits certain types of side effects common in older psychiatric drugs.

| Parameter | Value |

|---|---|

| Bioavailability | 63% (Extensive Metabolizers) to 94% (Poor Metabolizers) |

| Protein Binding | 98.5% (primarily to Albumin) |

| Half-life | 5 hours (EMs) / 24 hours (PMs) |

| Tmax | 1 to 2 hours |

| Metabolism | Hepatic (CYP2D6) |

| Excretion | Renal (>80%), Fecal (<17%) |

• Molecular Formula: C17H21NO • HCl
• Molecular Weight: 291.82 g/mol
• Solubility: Soluble in water (27.8 mg/mL at 25°C).
• Structure: It is a white to practically white solid. It is the R-enantiomer of the compound.

Atomoxetine is classified as a Selective Norepinephrine Reuptake Inhibitor (SNRI). Within the field of ADHD treatment, it is categorized as a non-stimulant. It is chemically related to certain antidepressants (like fluoxetine) but is specifically optimized for its effects on the norepinephrine transporter to treat cognitive and behavioral symptoms of ADHD.