Fluoxetine, Oral Capsule

Medically reviewed by University of Illinois-Chicago, Drug Information Group on May 17, 2017Written by University of Illinois-Chicago, Drug Information Group

Important warnings

FDA warning: Suicidal thoughts and actions

  • This drug has a black box warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients about drug effects that may be dangerous.
  • Fluoxetine can increase the risk of suicidal thinking and behavior. This risk is especially high in children, adolescents, and young adults. The risk is higher during the first few months of treatment with this drug. You’re also at higher risk if you have a personal or family history of bipolar illness or suicidal thoughts or actions. Your doctor and family should watch you closely when you start taking this drug and during dosage changes. They should watch for changes in your behavior or signs of worsening depression.

Other warnings

  • Serotonin syndrome warning: This drug can cause a life-threatening condition called serotonin syndrome. This syndrome happens when medications cause too much serotonin to build up in your body. Symptoms can include agitation, hallucinations (seeing or hearing something that isn’t there), problems with coordination, and a racing heart rate. They can also include overactive reflexes, fever, nausea, vomiting, or diarrhea. Call your doctor right away if you have any signs of this condition.
  • Mania warning: This drug may cause mania. Symptoms include greatly increased energy, extreme irritability, talking more or faster than usual, racing thoughts, or severe trouble sleeping.
  • Low salt levels warning: This drug may cause you to have dangerously low salt levels in your blood. Symptoms include headache, weakness, confusion, trouble concentrating, memory problems, and feeling unsteady. Call your doctor right away if you have any symptoms of this condition.

What is fluoxetine?

Fluoxetine is a prescription drug. It comes as a capsule, delayed-release capsule, tablet, and solution. All forms are taken by mouth. (A delayed-release capsule is released into your body more slowly.)

Fluoxetine oral capsule is available as the brand-name drugs Prozac and Prozac Weekly. It’s also available as a generic drug. Generic drugs usually cost less than brand-name versions. In some cases, they may not be available in every strength or form as brand-name drugs.

Fluoxetine oral capsule may be used as part of a combination therapy. This means you may need to take it with other medications. For the treatment of depressive episodes related to bipolar I disorder and treatment-resistant depression, this drug must be used with olanzapine.

Why it's used

Fluoxetine oral capsule is used to treat the following conditions:

  • Depression. This includes major depression, depressive episodes associated with bipolar I disorder, and treatment-resistant depression.
  • Obsessive-compulsive disorder. This condition causes bothersome thoughts that won’t go away (obsessions) and the need to do certain actions over and over (compulsions).
  • Bulimia nervosa. This condition is an eating disorder marked by binge eating followed by extreme behaviors to avoid gaining weight (purging, fasting, or excessive exercise).
  • Panic attacks. These are sudden episodes of extreme fear and worry even though no threat exists.
  • Mood-related symptoms of premenstrual dysphoric disorder. These symptoms include mood swings or episodes of excessive sadness, irritability, or anger.

How it works

Fluoxetine oral capsule belongs to a class of drugs called selective serotonin reuptake inhibitors (SSRIs). A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Fluoxetine works by increasing the amount of serotonin (a natural substance) in your brain. Serotonin helps maintain mental health balance. An increase in serotonin helps to treat symptoms of depression, obsessive-compulsive disorder, bulimia nervosa, and panic attacks. It also treats the mood-related symptoms of premenstrual dysphoric disorder.

Fluoxetine side effects

Fluoxetine oral capsule doesn’t cause drowsiness, but it can cause other side effects.

More common side effects

The more common side effects of fluoxetine can include:

  • strange dreams
  • decreased sex drive and trouble having an orgasm
  • decreased appetite
  • anxiety and nervousness
  • weakness
  • diarrhea
  • dry mouth
  • indigestion
  • flu
  • erectile dysfunction (trouble getting or keeping an erection)
  • trouble sleeping
  • nausea
  • sore throat
  • rash
  • watery nasal discharge
  • sleepiness
  • sweating and hot flashes
  • tremors (uncontrollable rhythmic movement in one part of your body)
  • yawning

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Serotonin syndrome. Symptoms can include:
    • agitation (feeling aggravated or restless)
    • hallucinations (seeing or hearing something that isn’t there)
    • problems with coordination
    • racing heart rate
    • overactive reflexes
    • fever
    • nausea
    • vomiting
    • diarrhea
  • Abnormal bleeding. Symptoms can include:
    • bruising or bleeding more easily than normal
  • Mania. Symptoms can include:
    • greatly increased energy
    • severe trouble sleeping
    • racing thoughts
    • reckless behavior
    • unusually grand ideas
    • excessive happiness or irritability
    • talking more or faster than normal
  • Seizures
  • Low salt levels in your blood. Symptoms can include:
    • headache
    • weakness
    • confusion
    • trouble concentrating
    • memory problems
    • feeling unsteady

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we can not guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Fluoxetine may interact with other medications

Fluoxetine oral capsule can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with fluoxetine are listed below.

Drugs you should not use with fluoxetine

Do not take these drugs with fluoxetine. Doing so can cause dangerous effects in your body. Examples of these drugs include:

  • Monoamine oxidase inhibitors (MAOIs), such as isocarboxazid, phenelzine, and tranylcypromine. You shouldn’t take fluoxetine if you take an MAOI or if you’ve stopped taking an MAOI within the last 2 weeks. Don’t take an MAOI within 5 weeks of stopping fluoxetine. Taking these drugs too close together could cause serious and life-threatening side effects. Symptoms include high fever, constant muscle spasms that you can’t control, and stiff muscles. They also include fast changes in your heart rate and blood pressure, confusion, and unconsciousness.
  • Thioridazine. You shouldn’t take these drugs together. Don’t take thioridazine within 5 weeks of stopping fluoxetine. Taking these drugs together can cause serious heart rhythm problems. These problems can cause you to die suddenly.
  • Pimozide. You shouldn’t take these drugs together. Fluoxetine can cause the levels of pimozide to increase in your body. This raises your risk for heart rhythm problems.

Interactions that increase your risk of side effects

Increased side effects: Taking fluoxetine with certain medications raises your risk of side effects. This is because fluoxetine and these other medications can cause the same side effects. These drugs include serotonergic drugs, such as:

  • selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine and sertraline
  • serotonin-norepinephrine reuptake inhibitors (SSNRIs) such as duloxetine and venlafaxine
  • tricyclic antidepressants (TCAs) such as amitriptyline and clomipramine
  • the opioids fentanyl and tramadol
  • the anxiolytic buspirone
  • triptans
  • lithium
  • tryptophan
  • St. John’s wort
  • amphetamines

Taking these drugs with fluoxetine may increase your risk of serotonin syndrome, which can be fatal. If you take any of these drugs, your doctor will start you on a lowered dosage of fluoxetine and monitor you for signs of serotonin syndrome. Symptoms can include agitation, sweating, muscle twitches, and confusion.

Increased side effects from other drugs: Taking fluoxetine with certain medications raises your risk of side effects from these drugs. Examples of these drugs include:

  • Tryptophan. Taking these drugs together may cause you to have agitation, restlessness, and stomach problems.
  • Benzodiazepines, such as triazolam and midazolam. Taking these drugs together may cause more sedation and drowsiness.
  • Warfarin. Taking these drugs together may cause an increase in bleeding. Your doctor will monitor you closely.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs). Taking these drugs together may cause an increase in bleeding. Your doctor will monitor you closely.
  • Aspirin. Taking these drugs together may cause an increase in bleeding. Your doctor will monitor you closely.
  • Drugs broken down by the enzyme CYPD2D6, such as aripiprazole, dextromethorphan, methadone, paliperidone, and risperidone. Taking these drugs with fluoxetine may increase your risk of serotonin syndrome, heart rhythm problems, and involuntary muscle movements.
  • Lithium. Your doctor should monitor your lithium blood levels if you need to take these drugs together.
  • Phenytoin. Taking these drugs together may cause confusion, dizziness, and fever. You may also have changes in your behavior. These changes include anger, irritability, or sadness.
  • Carbamazepine. Taking these drugs together can cause blurred vision, vertigo, or tremors.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we can not guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

Fluoxetine warnings

This drug comes with several warnings.

Allergy warning

This medication can cause a severe allergic reaction. Symptoms can include:

  • hives
  • rash alone or with a fever and joint pain
  • trouble breathing
  • swelling of your throat or tongue

If you develop these symptoms, call 911 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Warnings for people with certain health conditions

For people with blood clotting disorders: This drug may cause you to bleed more easily. If you take another drug to thin your blood, it could cause dangerous bleeding.

For people with diabetes: This drug may cause low blood sugar levels. Once you stop taking this drug, it may cause your blood sugar levels to increase.

For people with bipolar I disorder: You shouldn’t take this drug alone to treat depression associated with bipolar I disorder. This drug may increase your risk of a mixed or manic episode.

For people with liver disease: If you have liver problems or a history of liver disease, your body may not be able to process this drug as well. This may increase the levels of this drug in your body and cause more side effects. Your doctor may lower your dose or have you take this drug less often.

Warnings for other groups

For pregnant women: This drug is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should only be used if the potential benefit justifies the potential risk.

If you become pregnant while taking this drug, call your doctor right away.

For women who are breastfeeding: This drug may pass into breast milk and may cause side effects in a child who is breastfed. Talk to your doctor if you breastfeed your child. You may need to decide whether to stop breastfeeding or stop taking this medication.

For seniors: Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dosage or have you take the medication less often.

For children:

  • Bulimia nervosa, premenstrual dysphoric disorder, panic disorder, and treatment-resistant depression: This drug hasn’t been studied in children for these conditions. It shouldn’t be used in people younger than 18 years.
  • Major depressive disorder: This drug hasn’t been studied in children for this condition. It shouldn’t be used in children younger than 8 years.
  • Obsessive-compulsive disorder: This drug hasn’t been studied in children for this condition. It shouldn’t be used in children younger than 7 years.
  • Depressive episodes associated with bipolar I disorder: This drug hasn’t been studied in children for this condition. It shouldn’t be used in children younger than 10 years.

How to take fluoxetine

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

Dosage for bulimia nervosa

Generic: Fluoxetine

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg
  • Form: oral delayed-release capsule
  • Strength: 90 mg

Brand: Prozac

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg

Brand: Prozac Weekly

  • Form: oral delayed-release capsule
  • Strength: 90 mg

Adult dosage (ages 18–64 years)

Typical dosage: 60 mg per day taken in the morning.

Child dosage (ages 0–17 years)

This drug hasn’t been studied in children for this condition. It shouldn’t be used in people younger than 18 years.

Senior dosage (ages 65 years and older)

Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dosage or reduce how often you take the drug.

Dosage for premenstrual dysphoric disorder (PMDD)

Generic: Fluoxetine

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg
  • Form: oral delayed-release capsule
  • Strength: 90 mg

Adult dosage (ages 18–64 years)

  • Typical dosage: 20 mg per day taken every day. Or your doctor may give you this drug intermittently. You may start taking it 14 days before you expect your menstrual period to begin and stop taking it the first day of your period. You’ll take it once per day.
  • Maximum dosage: 80 mg per day.

Child dosage (ages 0–17 years)

This drug hasn’t been studied in children for this condition. It shouldn’t be used in people younger than 18 years.

Senior dosage (ages 65 years and older)

Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dosage or reduce how often you take the drug.

Dosage for major depressive disorder

Generic: Fluoxetine

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg
  • Form: oral delayed-release capsule
  • Strength: 90 mg

Brand: Prozac

    Form: oral capsule

  • Strengths: 10 mg, 20 mg, 40 mg

Brand: Prozac Weekly

  • Form: oral delayed-release capsule
  • Strength: 90 mg

Adult dosage (ages 18–64 years)

  • Typical dosage: 20–80 mg per day.
  • Maximum dosage: 80 mg per day.
  • Initial dosage: 20 mg per day taken in the morning.
  • Alternative dosage: You may be a candidate for taking this drug once per week. In this case, your doctor will stop your daily dose of the immediate-release capsules and switch you over to the delayed-release capsules. You’ll take 90 mg once per week. You’ll start taking it 7 days after your last daily dose of fluoxetine.

Child dosage (ages 8–17 years)

  • Typical dosage: 10–20 mg per day.
  • Initial dosage: After you take 10 mg per day for one week, your doctor may increase your dosage to 20 mg per day.

Child dosage (ages 0–7 years)

This drug hasn’t been studied in children for this condition. It shouldn’t be used in children younger than 8 years.

Senior dosage (ages 65 years and older)

Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dose or reduce how often you take the drug.

Dosage for obsessive-compulsive disorder

Generic: Fluoxetine

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg
  • Form: oral delayed-release capsule
  • Strength: 90 mg

Brand: Prozac

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg

Brand: Prozac Weekly

  • Form: oral delayed-release capsule
  • Strength: 90 mg

Adult dosage (ages 18–64 years)

  • Typical dosage: 20–80 mg per day.
  • Maximum dosage: 80 mg per day.
  • Initial dosage: 20 mg per day taken in the morning.
  • Alternative dosage: You may be a candidate for taking this drug once per week. In this case, your doctor will stop your daily dose of the immediate-release capsules and switch you over to the delayed-release capsules. You’ll take 90 mg once per week. You’ll start taking it 7 days after your last daily dose of fluoxetine.

Child dosage (ages 13–17 years and higher weight adolescents)

  • Typical dosage: 20–60 mg per day.
  • Initial dosage: 20 mg per day taken in the morning.

Child dosage (ages 7–12 and lower weight adolescents)

  • Typical dosage: 20–30 mg per day.
  • Initial dosage: 10 mg per day.

Child dosage (ages 0–6 years)

This drug hasn’t been studied in children for this condition. It shouldn’t be used in children younger than 7 years.

Senior dosage (ages 65 years and older)

Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dosage or reduce how often you take the drug.

Dosage for panic disorder

Generic: Fluoxetine

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg
  • Form: oral delayed-release capsule
  • Strength: 90 mg

Brand: Prozac

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg

Brand: Prozac Weekly

  • Form: oral delayed-release capsule
  • Strength: 90 mg

Adult dosage (ages 18–64 years)

  • Typical dosage: 20 mg per day.
  • Initial dosage: 10 mg per day.

Child dosage (ages 0–17 years)

This drug hasn’t been studied in children for this condition. It shouldn’t be used in people younger than 18 years.

Senior dosage (ages 65 years and older)

Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dosage or reduce how often you take the drug.

Dosage for depressive episodes associated with bipolar I disorder

Generic: Fluoxetine

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg
  • Form: oral delayed-release capsule
  • Strength: 90 mg

Brand: Prozac

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg

Brand: Prozac Weekly

  • Form: oral delayed-release capsule
  • Strength: 90 mg

Adult dosage (ages 18–64 years)

Fluoxetine must be taken in combination with the drug olanzapine.

  • Initial dosage: 20 mg of fluoxetine with 5 mg of olanzapine taken once per day.
  • When changing your dosage: Your doctor may increase your dosage of fluoxetine up to 50 mg per day. They may increase your dosage of olanzapine up to 12.5 mg per day.

Child dosage (ages 10–17 years)

Fluoxetine must be taken in combination with the drug olanzapine.

  • Initial dosage: 20 mg of fluoxetine with 2.5 mg of olanzapine taken once per day in the evening.

Child dosage (ages 0–9 years)

This drug hasn’t been studied in children for this condition. It shouldn’t be used in children younger than 10 years.

Senior dosage (ages 65 years and older)

Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dosage or reduce how often you take the drug.

Dosage for treatment-resistant depression

Generic: Fluoxetine

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg
  • Form: oral delayed-release capsule
  • Strength: 90 mg

Brand: Prozac

  • Form: oral capsule
  • Strengths: 10 mg, 20 mg, 40 mg

Brand: Prozac Weekly

  • Form: oral delayed-release capsule
  • Strength: 90 mg

Adult dosage (ages 18–64 years)

Fluoxetine must be taken in combination with the drug olanzapine.

  • Initial dosage: 20 mg of fluoxetine with 5 mg of olanzapine taken once per day.
  • When changing your dosage: Your doctor may increase your dosage of fluoxetine up to 50 mg per day. They may increase your dosage of olanzapine up to 20 mg per day.

Child dosage (ages 0–17 years)

This drug hasn’t been studied in children for this condition. It shouldn’t be used in people younger than 18 years.

Senior dosage (ages 65 years and older)

Seniors may have a higher risk of side effects from this drug. Because of this risk, your doctor may lower your dosage or reduce how often you take the drug.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we can not guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.

Take as directed

Fluoxetine oral capsule is used for short and long-term treatment of bulimia nervosa, premenstrual dysphoric disorder, major depression, and obsessive-compulsive disorder. It’s used for short-term treatment of panic attacks. It’s also used for short-term treatment of depressive episodes associated with bipolar I disorder and treatment-resistant depression with the drug olanzapine.

This drug comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all: If you don’t take this drug, the symptoms of your condition may not improve.

Don’t stop taking this drug without talking to your doctor first. Stopping this drug too quickly may cause serious symptoms. These can include:

  • anxiety
  • irritability
  • mood swings
  • restlessness
  • changes in your sleep habits
  • headache
  • sweating
  • nausea
  • dizziness

If you miss doses or don’t take the drug on schedule: Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much: You could have dangerous levels of the drug in your body. Symptoms of an overdose of this drug can include:

  • tiredness
  • vomiting
  • fast heart rate
  • nausea
  • dizziness
  • agitation
  • tremors

If you think you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 911 or go to the nearest emergency room right away.

What to do if you miss a dose: Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working: The symptoms of your condition should improve. However, you might not feel better right when you start taking this drug. It can take 1–4 weeks to start working.

Important considerations for taking fluoxetine

Keep these considerations in mind if your doctor prescribes fluoxetine for you.

General

  • You can take this drug with or without food.
  • Take this drug at the time(s) recommended by your doctor.
  • Don’t open the oral capsules or oral delayed-release capsules.

Storage

  • Store this drug at room temperature. Keep it between 59°F and 86°F (15°C and 30°C).
  • Keep this drug away from light.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t harm your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

You and your doctor should monitor certain health issues. This can help make sure you stay safe while you take this drug. These health issues include:

  • Mental health and behavioral problems. You and your doctor should watch for any unusual changes in your behavior and mood. This drug can cause new mental health and behavior problems. It may also worsen problems you already have.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained here in is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

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