Medication approval journey

fluoxetine (Prozac)

Approved for Major depressive disorder, acute and maintenance

FDA approvedSSRI antidepressantTaper risk: moderate

Before changing anything

Stopping abruptly causes withdrawal effects that can be severe

Stopping or reducing an SSRI too fast commonly causes withdrawal symptoms — dizziness, electric-shock sensations, insomnia, agitation. These are often more severe and far longer-lasting than the "one to two weeks" many people are told. Any change should be a slow, prescriber-supervised taper.

How long the trials actually ran

We could not establish a longest trial length for fluoxetine. That is a gap in what we can show you — not evidence that the trials ran long.

The label carries a clinical studies section describing the trials the approval rested on.

The gap between how long the trials ran and how long people actually take these medications is the single most important thing on this page. It is not evidence that longer use is unsafe or ineffective. It is evidence that longer use was not what got tested.

The boxed warning

The strongest warning the FDA puts on a label, reproduced word for word — not our summary of it.

WARNING: SUICIDAL THOUGHTS AND BEHAVIORS Antidepressants increased the risk of suicidal thoughts and behavior in children, adolescents, and young adults in short-term studies. These studies did not show an increase in the risk of suicidal thoughts and behavior with antidepressant use in patients over age 24; there was a reduction in risk with antidepressant use in patients aged 65 and older [see Warnings and Precautions (5.1) ] . In patients of all ages who are started on antidepressant therapy, monitor closely for worsening and for emergence of suicidal thoughts and behaviors. Advise families and caregivers of the need for close observation and communication with the prescriber [see Warnings and Precautions (5.1) ] . Fluoxetine is not approved for use in children less than 7 years of age [see Warnings and Precautions (5.1) and Use in Specific Populations (8.4) ] . When using fluoxetine and olanzapine in combination, also refer to Boxed Warning section of the package insert for Symbyax. WARNING: SUICIDAL THOUGHTS AND BEHAVIORS See full prescribing information for complete boxed warning. Increased risk of suicidal thinking and behavior in children, adolescents, and young adults taking antidepressants ( 5.1 ). Monitor for worsening and emergence of suicidal thoughts and behaviors ( 5.1 ). When using fluoxetine and olanzapine in combination, also refer to Boxed Warning section of the package insert for Symbyax.
Symbyax Sarafem

FDA label effective August 20, 2026read the full label on DailyMed

How many Americans take fluoxetine

Survey-based federal estimates, published with a lag of about two years. They count prescriptions filled, not outcomes.

29,517,275
prescriptions in the United States (2024)
6,177,251
people filling them (2024)

Prescriptions are up 24% since 2014. Whatever you decide about fluoxetine, you are deciding alongside about 6,177,251 other people this year.

Source: ClinCalc DrugStats (Medical Expenditure Panel Survey (MEPS), Agency for Healthcare Research and Quality), CC BY-SA 4.0, release 2026.08.

What people report to the FDA about fluoxetine

Read this before the numbers.

Anyone can file an adverse event report — patients, doctors, manufacturers — and nobody verifies that the drug caused what was reported. There is no denominator: tens of millions of prescriptions generate reports at an unknowable rate, and reporting rises with news coverage, not necessarily with harm. Counts below are report volumes, not rates, and cannot be compared between drugs. The FDA itself says not to use this data to make medical decisions — we show it because you deserve to see what is in the public record, with its limits stated plainly.

131,850
reports mentioning fluoxetine, all time
94,043
filed as serious (a report-level flag covering every drug and outcome in the report)

Most-reported reactions

  • Drug ineffective8,385
  • Nausea7,751
  • Fatigue7,713
  • Headache6,586
  • Depression6,136
  • Anxiety5,974
  • Dizziness5,412
  • Diarrhoea5,372
  • Off label use5,201
  • Pain5,185

“Drug ineffective” ranking this high is worth noticing: a report of not being helped counts as an adverse event too, and people file them in large numbers.

Source: FDA Adverse Event Reporting System (FAERS), via openFDA, data through 2026-07-30.

Known interactions, from the label

The FDA label’s interactions section, verbatim. A pharmacist checking your actual medication list beats any published list — including this one.

Read the label’s interactions section

7 DRUG INTERACTIONS As with all drugs, the potential for interaction by a variety of mechanisms (e.g., pharmacodynamic, pharmacokinetic drug inhibition or enhancement, etc.) is a possibility. Monoamine Oxidase Inhibitors (MAOIs): ( 2.9 , 2.10 , 4.1 , 5.2 ) Drugs Metabolized by CYP2D6: Fluoxetine is a potent inhibitor of CYP2D6 enzyme pathway ( 7.7 ) Tricyclic Antidepressants (TCAs): Monitor TCA levels during coadministration with fluoxetine or when fluoxetine has been recently discontinued ( 5.2 , 7.7 ) CNS Acting Drugs: Caution should be used when taken in combination with other centrally acting drugs ( 7.2 ) Benzodiazepines: Diazepam – increased t½, alprazolam - further psychomotor performance decrement due to increased levels ( 7.7 ) Antipsychotics: Potential for elevation of haloperidol and clozapine levels ( 7.7 ) Anticonvulsants: Potential for elevated phenytoin and carbamazepine levels and clinical anticonvulsant toxicity ( 7.7 ) Serotonergic Drugs: ( 2.9 , 2.10 , 4.1 , 5.2 ) Drugs that Interfere with Hemostasis (e.g. NSAIDs, Aspirin, Warfarin): May potentiate the risk of bleeding ( 7.4 ) Drugs Tightly Bound to Plasma Proteins: May cause a shift in plasma concentrations ( 7.6 , 7.7 ) Olanzapine: When used in combination with fluoxetine, also refer to the Drug Interactions section of the package insert for Symbyax ( 7.7 ) Drugs that Prolong the QT Interval: Do not use fluoxetine with thioridazine or pimozide. Use with caution in combination with other drugs that prolong the QT interval ( 4.2 , 5.11 , 7.7 , 7.8 )

7.1 Monoamine Oxidase Inhibitors (MAOI) [See Dosage and Administration (2.9 , 2.10) , Contraindications (4.1) , and Warnings and Precautions (5.2) ].

7.2 CNS Acting Drugs Caution is advised if the concomitant administration of fluoxetine and such drugs is required. In evaluating individual cases, consideration should be given to using lower initial doses of the concomitantly administered drugs, using conservative titration schedules, and monitoring of clinical status [see Clinical Pharmacology (12.3) ] .

7.3 Other Serotonergic Drugs The concomitant use of serotonergic drugs (including other SSRIs, SNRIs, triptans, tricyclic antidepressants, opioids, lithium, buspirone, amphetamines, tryptophan, and St. John's Wort) with fluoxetine increases the risk of serotonin syndrome. Monitor patients for signs and symptoms of serotonin syndrome, particularly during treatment initiation and dosage increases. If serotonin syndrome occurs, consider discontinuation of fluoxetine and/or concomitant serotonergic drugs [see Warnings and Precautions (5.2) ].

7.4 Drugs that Interfere with Hemostasis (e.g., NSAIDS, Aspirin, Warfarin) Serotonin release by platelets plays an important role in hemostasis. Epidemiological studies of the case-control and cohort design that have demonstrated an association between use of psychotropic drugs that interfere with serotonin reuptake and the occurrence of upper gastrointestinal bleeding have also shown that concurrent use of an NSAID or aspirin may potentiate this risk of bleeding. Altered anticoagulant effects, including increased bleeding, have been reported when SNRIs or SSRIs are coadministered with warfarin. Patients receiving warfarin therapy should be carefully monitored when fluoxetine is initiated or discontinued [see Warnings and Precautions (5.7) ] .

7.5 Electroconvulsive Therapy (ECT) There are no clinical studies establishing the benefit of the combined use of ECT and fluoxetine. There have been rare reports of prolonged seizures in patients on fluoxetine receiving ECT treatment.

7.6 Potential for Other Drugs to affect Fluoxetine Drugs Tightly Bound to Plasma Proteins — Because fluoxetine is tightly bound to plasma proteins, adverse effects may result from displacement of protein-bound fluoxetine by other tightly-bound drugs [see Clinical Pharmacology (12.3) ] .

7.7 Potential for Fluoxetine to affect Other Drugs Pimozide — Concomitant use in patients taking pimozide is contraindicated. Pimozide can prolong the QT interval. Fluoxetine can increase the level of pimozide through inhibition of CYP2D6. Fluoxetine can also prolong the QT interval. Clinical studies of pimozide with other antidepressants demonstrate an increase in drug interaction or QT prolongation. While a specific study with pimozide and fluoxetine has not been conducted, the potential for drug interactions or QT prolongation warrants restricting the concurrent use of pimozide and fluoxetine Thioridazine — Thioridazine should not be administered with fluoxetine or within a minimum of 5 weeks after fluoxetine has been discontinued, because of the risk of QT Prolongation [see Contraindications (4.2) , Warnings and Precautions (5.11) , and Drug Interactions (7.8)]. In a study of 19 healthy male subjects, which included 6 slow and 13 rapid hydroxylators of debrisoquin, a single 25 mg oral dose of thioridazine produced a 2.4-fold higher Cmax and a 4.5-fold higher AUC for thioridazine in the slow hydroxylators compared with the rapid hydroxylators. The rate of debrisoquin hydroxylation is felt to depend on the level of CYP2D6 isozyme activity. Thus, this study suggests that drugs which inhibit CYP2D6, such as certain SSRIs, including fluoxetine, will produce elevated plasma levels of thioridazine. Thioridazine administration produces a dose-related prolongation of the QT interval, which is associated with serious ventricular arrhythmias, such as Torsades de Pointes-type arrhythmias, and sudden death. This risk is expected to increase with fluoxetine-induced inhibition of thioridazine metabolism. Drugs Metabolized by CYP2D6 — Fluoxetine inhibits the activity of CYP2D6, and may make individuals with normal CYP2D6 metabolic activity resemble a poor metabolizer. Coadministration of fluoxetine with other drugs that are metabolized by CYP2D6, including certain antidepressants (e.g., TCAs), antipsychotics (e.g., phenothiazines and most atypicals), and antiarrhythmics (e.g., propafenone, flecainide, and others) should be approached with caution. Therapy with medications that are predominantly metabolized by the CYP2D6 system and that have a relatively narrow therapeutic index (see list below) should be initiated at the low end of the dose range if a patient is receiving fluoxetine concurrently or has taken it in the previous 5 weeks. Thus, his/her dosing requirements resemble those of poor metabolizers. If fluoxetine is added to the treatment regimen of a patient already receiving a drug metabolized by CYP2D6, the need for decreased dose of the original medication should be considered. Drugs with a narrow therapeutic index represent the greatest concern (e.g., flecainide, propafenone, vinblastine, and TCAs). Due to the risk of serious ventricular arrhythmias and sudden death potentially associated with elevated plasma levels of thioridazine, thioridazine should not be administered with fluoxetine or within a minimum of 5 weeks after fluoxetine has been discontinued [see Contraindications (4.2)]. Tricyclic Antidepressants (TCAs) — In 2 studies, previously stable plasma levels of imipramine and desipramine have increased greater than 2- to 10-fold when fluoxetine has been administered in combination. This influence may persist for 3 weeks or longer after fluoxetine is discontinued. Thus, the dose of TCAs may need to be reduced and plasma TCA concentrations may need to be monitored temporarily when fluoxetine is coadministered or has been recently discontinued [see Warnings and Precautions (5.2) and Clinical Pharmacology (12.3) ]. Benzodiazepines — The half-life of concurrently administered diazepam may be prolonged in some patients [see Clinical Pharmacology (12.3)] . Coadministration of alprazolam and fluoxetine has resulted in increased alprazolam plasma concentrations and in further psychomotor performance decrement due to increased alprazolam levels. Antipsychotics — Some clinical data suggests a possible pharmacodynamic and/or pharmacokinetic interaction between SSRIs and antipsychotics. Elevation of blood levels of haloperidol and clozapine has been observed in patients receiving concomitant fluoxetine. Anticonvulsants — Patients on stable doses of phenytoin and carbamazepine have developed elevated plasma anticonvulsant concentrations and clinical anticonvulsant toxicity following initiation of concomitant fluoxetine treatment. Lithium — There have been reports of both increased and decreased lithium levels when lithium was used concomitantly with fluoxetine. Cases of lithium toxicity and increased serotonergic effects have been reported. Lithium levels should be monitored when these drugs are administered concomitantly [see Warnings and Precautions (5.2)]. Drugs Tightly Bound to Plasma Proteins — Because fluoxetine is tightly bound to plasma proteins, the administration of fluoxetine to a patient taking another drug that is tightly bound to protein (e.g., Coumadin, digitoxin) may cause a shift in plasma concentrations potentially resulting in an adverse effect [see Clinical Pharmacology (12.3)]. Drugs Metabolized by CYP3A4 — In an in vivo interaction study involving coadministration of fluoxetine with single doses of terfenadine (a CYP3A4 substrate), no increase in plasma terfenadine concentrations occurred with concomitant fluoxetine. Additionally, in vitro studies have shown ketoconazole, a potent inhibitor of CYP3A4 activity, to be at least 100 times more potent than fluoxetine or norfluoxetine as an inhibitor of the metabolism of several substrates for this enzyme, including astemizole, cisapride, and midazolam. These data indicate that fluoxetine’s extent of inhibition of CYP3A4 activity is not likely to be of clinical significance. Olanzapine — Fluoxetine (60 mg single dose or 60 mg daily dose for 8 days) causes a small (mean 16%) increase in the maximum concentration of olanzapine and a small (mean 16%) decrease in olanzapine clearance. The magnitude of the impact of this factor is small in comparison to the overall variability between individuals, and therefore dose modification is not routinely recommended. When using fluoxetine and olanzapine and in combination, also refer to the Drug Interactions section of the package insert for Symbyax.

7.8 Drugs that Prolong the QT Interval Do not use fluoxetine in combination with thioridazine or pimozide. Use fluoxetine with caution in combination with other drugs that cause QT prolongation. These include: specific antipsychotics (e.g., ziprasidone, iloperidone, chlorpromazine, mesoridazine, droperidol); specific antibiotics (e.g., erythromycin, gatifloxacin, moxifloxacin, sparfloxacin); Class 1A antiarrhythmic medications (e.g., quinidine, procainamide); Class III antiarrhythmics (e.g., amiodarone, sotalol); and others (e.g., pentamidine, levomethadyl acetate, methadone, halofantrine, mefloquine, dolasetron mesylate, probucol or tacrolimus). Fluoxetine is primarily metabolized by CYP2D6. Concomitant treatment with CYP2D6 inhibitors can increase the concentration of fluoxetine. Concomitant use of other highly protein-bound drugs can increase the concentration of fluoxetine [see Contraindications (4.2) , Warnings and Precautions (5.11) , Drug Interactions (7.7) , and Clinical Pharmacology (12.3) ].

FDA label for fluoxetine, effective August 20, 2026DailyMed.

Who pays for fluoxetine

Two claims datasets and one survey, covering different populations with different instruments — they cannot be reconciled by arithmetic, and where their sum crowds the all-payer estimate, that is a finding about the estimates rather than a percentage.

Medicare Part D · claims · 2024Medicaid · claims floor · 2024All-payer · survey · 2024Commercially insured adults · not publishedChildren · no per-drug data
Medicare Part D
Read the under-65 group correctly before the numbers: Medicare before 65 means the disabled and dual-eligible population — among the sickest, highest-need people in the program — and reading their utilization as typical adult use would be a category error. The beneficiary total sums brand-level rows, so treat it as an upper bound on distinct people. 1,487,371 beneficiaries filled 7,496,788 claims in 2024 1,146,172 aged 65 and over, and 341,199 under 65.
Medicaid
At least 6,359,320 prescriptions in 2024 — a floor, because 143 of 1,157 national data rows are suppressed for privacy and contribute zero. Medicaid covers more children than any insurer in the country and publishes no age split — how much of this number is pediatric use is not knowable from public data.
All payers (survey estimate)
The MEPS-based estimate above puts the whole country at 29,517,275 prescriptions and 6,177,251 people in 2024. Subtracting the public programs from it would produce a number for everyone else — and we do not print that number, because subtracting a survey from claims counts manufactures precision that does not exist.
The population nobody counts
The commercially insured working-age adult — statistically, the likeliest person to be reading this page — is the one population with no public per-drug count anywhere. Private claims data exists and is sold, but nothing a patient can check is published. For children the record is thinner still: no public source counts pediatric use of fluoxetine specifically; the closest the public record comes is condition-level treatment rates for children, which we have traced for one condition in how childhood ADHD got counted.

Sources: Medicare Part D Prescribers — by Geography and Drug, data.cms.gov, National rows, data year 2024 (published with ~17-month lag). Medicaid State Drug Utilization Data 2024, data.medicaid.gov, national aggregate rows. Retrieved 2026-09-01.

The approval, step by step

  1. Step 1

    What the approval was actually based on

    Which studies did the FDA rely on, how long did they run, and who was in them?

    Efficacy for PROZAC was established for the: Acute and maintenance treatment of Major Depressive Disorder in adults, and children and adolescents (8 to 18 years) in 7 short-term and 2 long-term, placebo-controlled trials [see Clinical Studies 14.1].

    FDA-approved labelling, 14 CLINICAL STUDIESread the label on DailyMed

    Our reading

    A stronger package than most: nine trials, two of them long-term, and the FDA gave it priority review. Fluoxetine is the drug in this class with the most approval-era evidence behind it, which is worth knowing if you are comparing options rather than comparing a drug against nothing.

  2. Step 2

    The approval

    When was it approved, under what application, and by whose review?

    Approved
    December 29, 1987
    Application
    NDA018936
    Review
    PRIORITY
    Original sponsor
    Eli Lilly and Company
    Holds it now
    Eli Lilly and Company
    Label submissions since
    89

    Source: openFDA Drugs@FDA, original application ORIG-1

  3. Step 3

    What was added after it was on the market

    Which warnings arrived only after millions of people were already taking it?

  4. Step 4

    What independent research has found since

    What has been learned by people who were not selling it?

  5. Step 5

    What still is not known

    Which questions you might reasonably have has nobody answered yet?

    • The boxed warning about suicidal thoughts in under-25s arrived in 2005, eighteen years after approval. What changed — the drug, or what was measured?
    • What does "long-term" mean in the two long-term trials, and does it match how long you have been taking it?

The legal and safety record

Settled and adjudicated matters only, from primary sources — including the litigation that was decided for the manufacturer, and the cases this drug is verifiably not part of.

Read the fluoxetine legal and safety record

Deciding about fluoxetine?

Open fluoxetine (Prozac) in Resolv

The app has the full approval journey, the resources behind it, and people working through the same questions.

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