Reviewed on 6/27/2022

What Is Fluoxetine and How Does It Work?

Fluoxetine is a prescription medication used to treat the symptoms of major depressive disorder, obsessive-compulsive disorder, bulimia nervosa, panic disorder, and premenstrual dysphoric disorder.

Fluoxetine may improve your mood, sleep, appetite, and energy level and may help restore your interest in daily living. It may also decrease fear, anxiety, unwanted thoughts, and the number of panic attacks. It may also reduce the urge to perform repeated tasks (compulsions such as hand-washing, counting, and checking) that interfere with daily living. Fluoxetine may lessen premenstrual symptoms such as irritability, increased appetite, and depression. It may decrease binging and purging behaviors in bulimia.

  • Fluoxetine is available under the following different brand names: Prozac, Sarafem, Prozac Weekly, Selfemra

What Are Side Effects Associated with Using Fluoxetine?

Common side effects of Fluoxetine include:

  • sleep problems, 
  • strange dreams
  • headache, 
  • dizziness, 
  • drowsiness, 
  • vision changes, 
  • tremors or shaking, 
  • anxiety, 
  • nervousness, 
  • pain, 
  • weakness, 
  • yawning
  • tiredness, 
  • upset stomach, 
  • loss of appetite, 
  • nausea, 
  • vomiting, 
  • diarrhea, 
  • dry mouth
  • sweating, 
  • hot flashes
  • changes in weight or appetite, 
  • stuffy nose
  • sinus pain, 
  • sore throat
  • flu symptoms, 
  • decreased sex drive, 
  • impotence, and
  • difficulty having an orgasm

Serious side effects of Fluoxetine include:

  • hives, 
  • difficulty breathing, 
  • swelling of face, lips, tongue, or throat, 
  • fever, 
  • sore throat, 
  • burning eyes, 
  • skin pain, 
  • red or purple skin rash with blistering and peeling, 
  • mood or behavior changes, 
  • anxiety, 
  • panic attacks, 
  • trouble sleeping, 
  • impulsiveness, 
  • irritableness, 
  • agitation, 
  • hostility, 
  • aggression, 
  • restlessness, 
  • hyperactivity (mentally or physically), 
  • increase depression, 
  • thoughts of suicide or self-harm, 
  • blurred vision, 
  • tunnel vision
  • eye pain or swelling, 
  • seeing halos around lights, 
  • fast, uneven, or pounding heartbeats, 
  • fluttering in your chest, 
  • shortness of breath, 
  • sudden dizziness, 
  • headache, 
  • confusion, 
  • slurred speech, 
  • severe weakness, 
  • vomiting, 
  • loss of coordination, 
  • feeling unsteady, 
  • very stiff (rigid) muscles, 
  • high fever, 
  • sweating, 
  • confusion, 
  • tremors, 
  • lightheadedness
  • hallucinations, 
  • shivering, 
  • twitching
  • nausea, 
  • vomiting, and 
  • diarrhea

Rare side effects of Fluoxetine include:

  • none 

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; sudden dizziness, lightheartedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Are Dosages of Fluoxetine?

Adult dosage


  • 10 mg
  • 20 mg
  • 40 mg


  • 10 mg
  • 20 mg
  • 60 mg

Capsule, delayed-release

  • 90 mg

Oral solution

  • 20 mg/5mL

Pediatric Dosage


  • 10 mg
  • 20 mg
  • 40 mg


  • 10 mg
  • 20 mg
  • 60 mg

Oral Solution

  • 20 mg/5mL

Major Depressive Disorder

  • Initial: 20 mg orally once daily
  • May consider gradually increasing the dose after several weeks by 20 mg/day, not to exceed 80 mg each day
  • Prozac Weekly: 90mg orally once per week
  • Children older than 8 years of age: 10-20 mg orally once daily initially
  • Start at 10mg/day in lower-weight children
  • May gradually increase the dose after 1 week; not to exceed 20mg per day

Obsessive-Compulsive Disorder

  • Initial: 20 mg orally once daily
  • May consider gradually increasing the dose after several weeks by 20 mg/day (20 mg-60 mg/day recommended range), not to exceed 80mg each day
  • Children older than 7 years of age: 10 mg orally once daily initially.  May increase dose after 2 weeks to 20 mg daily; further increases may be considered after several weeks
  • Adolescents and high-weight children: typical dose range 20-60 mg daily
  • Lower weight children: Typical dosage range 20-30 mg daily

Bulimia Nervosa

  • Initial or maintenance: may titrate dose to 60 mg orally once daily over several days

Panic Disorder

  • Initial: 10 mg orally once daily 
  • May consider gradually increasing the dose after several weeks; not to exceed 60mg daily, doses over 60mg/day are not evaluated

Premenstrual Dysphoric Disorder

  • Continuous (Sarafem): 20 mg orally once daily initially; may gradually increase the dose; not to exceed 80mg/day or
  • Intermittent (Sarafem): 20 mg orally once daily starting 14 days before menstruation and through the first full day of menses (repeat each cycle)

Fibromyalgia (Off-label)

  • 20-80 mg orally each day

Dosing considerations

Efficacy may increase with concomitant amitriptyline

Migraine (Off-label)


  • 20-40 mg orally each day

Hot Flashes Caused by Hormonal Chemotherapy (Off-label)

  • 20 mg/day orally for 4 weeks

Raynaud Phenomenon (Off-label)

  • 20-60 mg/day orally

Dosing Modifications

Upon therapy discontinuation, taper gradually over 4-6 months to minimize the incidence of withdrawal symptoms and allow for detection of re-emerging symptoms; if withdrawal symptoms are intolerable, following a dose reduction, resume the previously prescribed dose and/or decrease the dose at a more gradual rate.

Renal impairment: Use caution; drug accumulation may occur with severe renal impairment.

Hepatic impairment (cirrhosis): Decreased clearance of parent drug and active metabolite (norfluoxetine); lower or less frequent dose recommended.

Geriatric dosage considerations

  • Initial 10 mg orally per day, may gradually increase the dose by 10-20 mg after several weeks as tolerated
  • Do not take it at night unless sedation occurs

What Other Drugs Interact with Fluoxetine?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them.  Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first

  • Fluoxetine has severe interactions with at least 14 other drugs.
  • Fluoxetine has serious interactions with at least 116 other drugs.
  • Fluoxetine has moderate interactions with at least 286 other drugs.
  • Fluoxetine has minor interactions with at least 39 other drugs.

This information does not contain all possible interactions or adverse effects.  Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all the products you use.  Keep a list of all your medications with you, and share this information with your doctor and pharmacist.  Check with your health care professional or doctor for additional medical advice, or if you have health questions or concerns.

What Are Warnings and Precautions for Fluoxetine?


  • Hypersensitivity
  • Concomitant pimozide or thioridazine (within 5 weeks of administering Fluoxetine)
  • Breastfeeding
  • Coadministration with MAOIs
    • Coadministration may cause serotonin syndrome
    • Coadministration of MAOIs with fluoxetine or within 5 weeks of discontinuing fluoxetine
    • Initiating fluoxetine within 14 days of administering an MAOI
    • Starting fluoxetine in a patient who is being treated with linezolid or IV methylene blue is contraindicated because of an increased risk of serotonin syndrome
    • If linezolid or IV methylene blue must be administered, discontinue fluoxetine immediately and monitor for CNS toxicity; may resume fluoxetine 24 hr after last linezolid or methylene blue dose or after 5 weeks of monitoring, whichever comes first

Effects of drug abuse

  • None

Short-Term Effects

  • See "What Are Side Effects Associated with Using Fluoxetine?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Fluoxetine?"


  • Clinical worsening and suicidal ideation may occur despite medication in adolescents and young adults (aged 18-24 years)
  • Development of potentially life-threatening serotonin syndrome reported with SNRIs and SSRIs alone but particularly with concomitant use of other serotonergic drugs (including triptans, tricyclic antidepressants, fentanyl, lithium, tramadol, tryptophan, buspirone, amphetamines, and St. John's wort) if concomitant use with these types of drugs is clinically warranted, inform patients of potential increased risk for serotonin syndrome, particularly during treatment initiation and dose increases (see Contraindications and Drug Interactions)
  • Risk of bleeding (GI and other) when used in combination with NSAIDs, aspirin, or drugs affecting coagulation; may impair platelet aggregation
  • Activation of mania/hypomania (screen for bipolar disorder)
  • Fluoxetine therapy has been associated with occurrence of rash and allergic reaction, including vasculitis; discontinue if they occur
  • Bone fractures have been associated with antidepressant therapy; consider possibility of bone fracture when patient presents with bone pain
  • May cause or exacerbate sexual dysfunction
  • Use caution in patients with risk for QT prolongation, including congenital long QT syndrome, history of prolonged QT, or history of prolonged QT; QT prolongation and ventricular arrhythmia, including torsade de pointes
  • Hyponatremia reported with use; consider discontinuation if symptomatic hyponatremia occurs
  • Use caution in patients with a history of seizure disorders
  • May prolong QT interval and cause ventricular arrhythmia, including torsade de pointes
  • May cause nervousness, anxiety, insomnia, or anorexia
  • Risk of mydriasis; may trigger angle closure attack in patients with angle closure glaucoma with anatomical narrow angles without a patent iridectomy
  • Hypoglycemia reported; may alter glycemic control in patients with diabetes
  • Conflicting evidence reported regarding use of SSRIs during pregnancy and increased risk of persistent pulmonary hypertension of the newborn, or PPHN (see Pregnancy)
  • Risk of complications in neonates exposed to SNRIs/SSRIs late in third trimester (feeding difficulties, irritability, and respiratory problems)
  • Wait 1 week after discontinuation of Prozac before starting Prozac Weekly
  • Gradually decrease dose when discontinuing
  • Has long half-life, decrease in dose will not be fully reflected in plasma for several weeks
  • Conditions that predispose to QT prolongation and ventricular arrhythmia; such conditions include concomitant use of drugs that prolong the QT interval; hypokalemia or hypomagnesemia; recent myocardial infarction, uncompensated heart failure, bradyarrhythmia, and other significant arrhythmias
  • Consider ECG assessment and periodic ECG monitoring if initiating treatment with fluoxetine in patients with risk factors for QT prolongation and ventricular arrhythmia; consider discontinuing fluoxetine and obtaining a cardiac evaluation if patients develop signs or symptoms consistent with ventricular arrhythmia

Sexual dysfunction

  • Use may cause symptoms of sexual dysfunction in both male and female patients; inform patients that they should discuss any changes in sexual function and potential management strategies with their healthcare provider
  • Use of SSRIs, may cause symptoms of sexual dysfunction; in male patients, SSRI use may result in ejaculatory delay or failure, decreased libido, and erectile dysfunction
  • In female patients, SSRI/SNRI use may result in decreased libido and delayed or absent orgasm
  • Important for prescribers to inquire about sexual function prior to initiation of therapy and to inquire specifically about changes in sexual function during treatment because sexual function may not be spontaneously reported
  • When evaluating changes in sexual function, obtaining a detailed history (including timing of symptom onset) is important because sexual symptoms may have other causes, including underlying psychiatric disorder
  • Discuss potential management strategies to support patients in making informed decisions about treatment

Pregnancy and Lactation

  • A pregnancy exposure registry monitors pregnancy outcome in women exposed to antidepressants during pregnancy; healthcare providers are encouraged to register patients by calling the National Pregnancy Registry for Antidepressants at 1-844-405-6185 or visiting online at https://womensmentalhealth.org/clinical-and-researchprograms/pregnancyregistry/antidepressants
  • Available data from published epidemiologic studies and post-marketing reports over several decades have not established an increased risk of major birth defects or miscarriage; some studies have reported an increased incidence of cardiovascular malformations; however, these studies results do not establish a causal relationship
  • There are risks associated with untreated depression in pregnancy and risks of persistent pulmonary hypertension of the newborn (PPHN) and poor neonatal adaptation with exposure to selective serotonin reuptake inhibitors (SSRIs), during pregnancy
  • Women who discontinue antidepressants during pregnancy are more likely to experience a relapse of major depression than women who continue antidepressants; this finding is from a prospective, longitudinal study that followed 201 pregnant women with a history of major depressive disorder who were euthymic and taking antidepressants at beginning of pregnancy
  • Consider the risk of untreated depression when discontinuing or changing treatment with antidepressant medication during pregnancy and postpartum.
  • Neonates exposed to drug and other SSRI or SNRIs late in the third trimester have developed complications requiring prolonged hospitalization, respiratory support, and tube feeding; such complications can arise immediately upon delivery; reported clinical findings have included respiratory distress, cyanosis, apnea, seizures, temperature instability, feeding difficulty, vomiting, hypoglycemia, hypotonia, hypertonia, hyperreflexia, tremors, jitteriness, irritability, and constant crying
  • These findings are consistent with either a direct toxic effect of SSRIs and SNRIs or possibly a drug discontinuation syndrome; it should be noted that, in some cases, the clinical picture is consistent with serotonin syndrome
  • Persistent pulmonary hypertension of the newborn
    • Potential risk of PPHN when used during pregnancy
    • Initial public health advisory, in 2006, was based on a single published study; since then, there have been conflicting findings from new studies, making it unclear whether the use of SSRIs during pregnancy can cause PPHN
    • The FDA has reviewed the new study results and has concluded that, given the conflicting results from different studies, it is premature to reach any conclusion about a possible link between SSRI use in pregnancy and PPHN
    • FDA recommendation: The FDA advises health-care professionals not to alter their current clinical practice of treating depression during pregnancy and to report any adverse events to the FDA MedWatch program
    • A meta-analysis of 7 observational studies, found exposure to SSRIs in late pregnancy (later than 20 weeks gestation) more than doubled the risk of PPHN that could not be explained by other etiologies (congenital malformations, meconium aspiration) (BMJ 2014;348:f6932)
    • Data from published literature report the presence of fluoxetine and norfluoxetine in human milk; there are reports of agitation, irritability, poor feeding, and poor weight gain in infants exposed to fluoxetine through breast milk
    • There are no data on effect of fluoxetine or its metabolites on milk production; developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for therapy and any potential adverse effects on breastfed child from drug or underlying maternal condition
    • Infants exposed to drug should be monitored for agitation, irritability, poor feeding, and poor weight

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