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How does this medication work? What will it do for me?

Atomoxetine belongs to a family of medications known as selective norepinephrine reuptake inhibitors. It is used to treat attention deficit hyperactivity disorder (ADHD). It helps to increase attention and decrease restlessness and impulsiveness in children and adults.

Other measures (e.g., psychological, educational, and social therapies) are used along with atomoxetine as part of an overall treatment program for ADHD. An improvement in ADHD symptoms generally occurs within 1 to 4 weeks of starting atomoxetine. This medication is not a stimulant.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

How should I use this medication?

The dose of atomoxetine depends on the needs of the person taking the medication. The daily dose of atomoxetine is based on body weight and is taken once daily or twice daily. The dose is started low and increased gradually. Doses above 100 mg daily are not recommended. Atomoxetine may be taken with or without food. Swallow the capsules whole, and do not open the capsules.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important that this medication be taken exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, and keep it out of the reach of children.

What form(s) does this medication come in?

Mylan-Atomoxetine is no longer being manufactured for sale in Canada. For brands that may still be available, search under atomoxetine. This article is being kept available for reference purposes only. If you are using this medication, speak with your doctor or pharmacist for information about your treatment options.

Who should NOT take this medication?

Do not take atomoxetine if you:

  • are allergic to atomoxetine or any ingredients of the medication
  • have an overactive thyroid gland
  • have advanced hardening of the arteries
  • have heart disease
  • have moderate-to-severe high blood pressure
  • have narrow-angle glaucoma
  • have a pheochromocytoma (a type of tumour of the adrenal glands)
  • have taken a type of medication known as an MAO inhibitor (e.g., phenelzine, tranylcypromine, moclobemide) within the past 2 weeks - do not start treatment with an MAO inhibitor until at least 2 weeks after discontinuing atomoxetine treatment

Do not give this medication to children under 6 years of age.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • constipation
  • decreased appetite
  • dry mouth
  • dizziness
  • erectile dysfunction (trouble getting or keeping an erection) or reduced sex drive
  • fatigue
  • low blood pressure (fainting or feeling lightheaded after getting up from a sitting or lying position)
  • nausea
  • painful menstruation (periods)
  • trouble sleeping
  • upset stomach
  • vomiting
  • weight loss

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • agitation
  • aggressive behaviour or hostility
  • difficulty urinating, emptying bladder
  • hallucinations (hearing or seeing things that aren't there)
  • increased blood pressure
  • palpitations (feeling your heart beat quickly or irregularly)
  • poor circulation in the extremities (e.g., cold or numb fingers or toes, discolouration, sores that won't heal)
  • signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
  • symptoms of liver damage (e.g., yellow skin or eyes, abdominal pain, loss of appetite, pale stools, dark urine)
  • symptoms of mania (e.g., unusually excited, overactive, uninhibited behavior, paranoia, delusions)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • an erection lasting longer than 4 hours
  • symptoms of a serious allergic reaction (e.g., hives, swelling of the face and throat, difficulty breathing)
  • thoughts of suicide or hurting yourself

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Behavioural and emotional changes: Atomoxetine may cause some people to experience unusual feelings of aggression, hostility, or anxiety. They may have hallucinations or have impulsive or disturbing thoughts of harming themselves. If you experience these side effects (or notice them in a family member who is taking this medication), contact your doctor immediately. Your doctor will monitor you closely for these side effects while you are taking this medication.

Blood pressure: People with low blood pressure or high blood pressure should be closely monitored by their doctor while they are taking this medication. This medication can increase blood pressure or can cause dizziness or fainting for people who have low blood pressure. If you have low blood pressure or high blood pressure, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Drowsiness/reduced alertness: Atomoxetine may affect the mental or physical abilities needed to drive or operate machinery. Avoid driving, operating machinery, or performing other hazardous tasks until you have determined how this medication affects you.

Exercise: If you participate in strenuous exercise or activities, consult your doctor before taking atomoxetine.

Growth and weight gain: This medication can cause children to lose weight and can slow their growth rate. Your doctor will monitor for slowed growth while they are taking this medication. Children who are not growing or gaining weight as expected may need to stop their treatment with this medication, as recommended by their doctor.

Heart problems: This medication can increase heart rate and blood pressure. It may also increase the risk of sudden death for people with heart problems. If you have heart problems, including an irregular heartbeat or a family history of sudden death related to heart disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Atomoxetine is generally not recommended for people with known structural heart abnormalities (such as abnormal size, missing or poorly functioning heart valves, or problems with blood vessels connected to the heart).

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. People with kidney problems may need lower doses of this medication. People with kidney problems should discuss with their doctor how this medication may affect their medical conditions, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. People with decreased liver function may require lower doses of this medication. In rare cases, atomoxetine may cause liver injury. Anyone taking atomoxetine should report yellow eyes or skin, dark urine, itching, upper-right abdominal pain, or unexplained flu-like symptoms to their doctor.

Long-term use: If you use this medication for a long period of time, you will need regular heart checkups by your doctor.

Suicidal or agitated behaviour: People taking this medication may feel agitated (restless, anxious, aggressive, emotional, and feeling not like themselves), or they may want to hurt themselves or others. If you experience these side effects or notice them in a family member who is taking this medication, contact your doctor immediately. You should be closely monitored by your doctor for emotional and behaviour changes while taking this medication.

Stopping the medication: Check with your doctor before stopping this medication.

Urinary Tract Problems: Atomoxetine can cause problems with bladder emptying and urinary tract function. If you experience difficulty starting to urinate or increased frequency of needing to urinate, contact your doctor.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if atomoxetine passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of this medication have not been established for young children. Atomoxetine should not be used by children under 6 years of age.

What other drugs could interact with this medication?

There may be an interaction between atomoxetine and any of the following:

  • abiraterone
  • amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
  • antiarrhythmics (e.g., amiodarone, disopyramide, dofetilide, flecainide, procainamide, quinidine, sotalol)
  • antipsychotics (e.g., aripiprazole, chlorpromazine, clozapine, haloperidol, thioridazine)
  • blood pressure medications
  • fast acting bronchodilators (e.g., salbutamol, terbutaline)
  • long acting bronchodilators (e.g., formoterol, salmeterol)
  • bupropion
  • caffeine
  • cinacalcet
  • darifenacin
  • darunavir
  • decongestant cold medications (e.g., phenylephrine, pseudoephedrine)
  • decongestant eye drops and nose sprays (e.g., naphazoline, oxymetazoline, xylometazoline)
  • dexmethylphenidate
  • duloxetine
  • linezolid
  • macrolide antibiotics (e.g., clarithromycin, erythromycin)
  • methadone
  • methylene blue
  • mirabegron
  • modafinil
  • monoamine oxidase inhibitors (MAOI; e.g., phenelzine, tranylcypromine, moclobemide, selegiline)
  • quinine
  • quinolone antibiotics (e.g., ciprofloxacin, ofloxacin,)
  • selective serotonin reuptake inhibitors (SSRIs; e.g., fluoxetine, paroxetine, sertraline)
  • theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
  • tyrosine kinase inhibitors (e.g., imatinib, lapatinib, nilotinib, pazopanib, sunitinib)

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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