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Prozac

(fluoxetine)

Prozac (fluoxetine); not controlled

Full Prescribing Information DailyMed Drug Information

Summary

Prozac is a selective serotonin reuptake inhibitor approved for major depressive disorder from 8 years of age and for obsessive-compulsive disorder from 7 years. Response is judged over weeks of continuous dosing. Its half-life is the longest in the class, so it is effectively self-tapering and forgiving of a missed dose. Not controlled; brand and generic.

Forms & Strengths

  • Capsules, immediate release: 10 mg, 20 mg, 40 mg
  • Tablets: 10 mg, 20 mg, 60 mg
  • Oral solution: 20 mg/5 mL (4 mg/mL)
  • Capsule, delayed release, once weekly: 90 mg. A separate label; NEVER studied in children
  • Olanzapine and fluoxetine capsules: fluoxetine 25 mg or 50 mg with olanzapine 3, 6 or 12 mg

Dosing

  • Age:
    • MDD: 8 y/o and older
    • OCD: 7 y/o and older
    • Bipolar I depression, with olanzapine: 10 y/o and older
  • Onset: 4 weeks or longer in MDD; 5 weeks or longer in OCD
  • Duration: continuous with once-daily dosing
  • Initial Dose:
    • Pediatric MDD: 10 or 20 mg/day; 10 mg/day if lower weight
    • Pediatric OCD: 10 mg/day at any weight
    • Adults: 20 mg/day
  • Titration:
    • Pediatric MDD: to 20 mg/day after 1 week; OCD: to 20 mg/day after 2 weeks
    • Further increases only after several more weeks, never weekly
  • Max Dose:
    • Ceiling at any age or indication: 80 mg/day
    • Pediatric OCD: 60 mg/day, or 30 mg/day if lower weight
    • Pediatric MDD: no separate maximum; trials used 10 to 20 mg/day
  • Considerations: Give in the morning; a dose above 20 mg/day may be split between morning and noon. Use a lower or less frequent dose in cirrhosis.

Pharmacology

  • Mechanism: Blocks presynaptic serotonin reuptake at SERT, without the tricyclics' anticholinergic and sedative burden
  • Delivery / Release: immediate release; food does not affect bioavailability
  • Metabolism: hepatic via CYP2D6 to active norfluoxetine. Half-life 4 to 6 days on chronic dosing, norfluoxetine 4 to 16 days, steady state at 4 to 5 weeks
  • Class Positioning: a POTENT CYP2D6 inhibitor persisting up to 5 weeks after the last dose, unlike Zoloft. The only SSRI with a pediatric MDD indication

Indications

  • Major Depressive Disorder (ICD-10: F32.x, F33.x): 8 y/o and older
  • Obsessive-Compulsive Disorder (ICD-10: F42.x): 7 y/o and older
  • Bulimia Nervosa (ICD-10: F50.2): adults only, at 60 mg/day
  • Panic Disorder (ICD-10: F41.0): adults only
  • Bipolar I depression, with olanzapine only (ICD-10: F31.x): 10 y/o and older
  • Treatment-resistant depression, with olanzapine only: adults

Off-Label Uses

  • Pediatric anxiety disorders (ICD-10: F41.1, F40.10, F93.0): supported; AHRQ graded SSRIs moderate to high, with CBT outperforming fluoxetine (AHRQ 2017). On-label alternative: Cymbalta from 7 y/o
  • MDD in CHILDREN rather than adolescents (ICD-10: F32.x): graded low in adolescents, INSUFFICIENT in children (AACAP 2023)
  • Bulimia nervosa in adolescents (ICD-10: F50.2): insufficient at any dose

Contraindications & Warnings

  • Boxed Warning: SUICIDAL THOUGHTS AND BEHAVIORS in children, adolescents and young adults.
    • Monitor closely for worsening and emergent suicidality in the initial few months and at every dose change, up or down.
    • Observation must include DAILY observation at home. Dispense the smallest quantity consistent with good management.
  • Contraindicated:
    • An MAOI concurrently, within 5 WEEKS of stopping Prozac, or Prozac within 14 days of an MAOI. That 5-week exit washout is longer than the rest of the class, set by norfluoxetine's half-life.
    • Linezolid or intravenous methylene blue.
    • Pimozide and thioridazine; fluoxetine raises both via CYP2D6 and all three prolong QT.
  • Use with caution:
    • Seizure history; long QT, hypokalemia, hypomagnesemia, recent myocardial infarction, heart failure, bradyarrhythmias.
    • Narrow angles without a patent iridectomy; diabetes; cirrhosis, needing a lower dose.
    • Underweight patients; NSAIDs, aspirin, anticoagulants, diuretics; prior rash on fluoxetine.
  • Screen before starting:
    • Personal and family history of bipolar disorder, mania or hypomania; baseline height, weight and sexual function.
    • QT risk factors, and a medication list for CYP2D6 substrates, MAOIs and anticoagulants.

Drug Interactions

  • MAOIs (phenelzine, selegiline, linezolid, methylene blue): contraindicated. 14 days before starting Prozac, 5 WEEKS after stopping it
  • CYP2D6 substrates including atomoxetine (Strattera, TCAs, antipsychotics): start low, and treat anyone dosed within the previous 5 weeks as still on fluoxetine.
    • For atomoxetine, lengthen the titration interval to 4 weeks rather than lowering the target dose.
    • This pair, and Qelbree, stack two pediatric suicidality boxed warnings.
  • Bupropion (Wellbutrin XL): doubles 2D6 inhibition and stacks seizure cautions
  • Other serotonergic drugs (SSRIs, SNRIs, triptans, tramadol, lithium, AMPHETAMINES): serotonin syndrome. Stop all for agitation, hyperthermia, rigidity or myoclonus
  • Tricyclics, phenytoin, carbamazepine: levels rise for weeks; check when fluoxetine starts and stops
  • NSAIDs, aspirin, warfarin: bleeding; check the INR at both ends
  • QT-prolonging drugs (ziprasidone, erythromycin, amiodarone, methadone): avoid, or obtain an ECG before each increase

Administration

  • Give once daily in the morning; split a dose above 20 mg for daytime nausea rather than reducing it.
  • With or without food. Swallow capsules and tablets whole; the oral solution is the only form delivering below 10 mg.
  • Missed dose: resume at the next dose; do not double up.
  • Never use the 90 mg once-weekly capsule in a pediatric patient or in place of daily dosing.
  • Switching to an MAOI: allow 5 weeks off fluoxetine. From an MAOI: allow 14 days.

Side Effects

  • Common: nausea, insomnia, nervousness, somnolence, anxiety, diarrhea, anorexia, dry mouth, tremor, asthenia.
    • Pediatric trials add thirst, hyperkinesia, agitation, epistaxis, urinary frequency and menorrhagia.
  • Serious:
    • Suicidal thoughts and behavior: the boxed warning. Change the regimen, including stopping, if suicidality emerges.
    • Serotonin syndrome: stop every serotonergic agent immediately and treat supportively.
    • Mania or hypomania, in 2.6% of pediatric patients. Stop and reassess for bipolar disorder.
    • Rash and systemic hypersensitivity. Discontinue on any unexplained rash.
    • Hyponatremia and SIADH; QT prolongation and torsades; seizures.
    • Growth lag: 1.1 cm and 1.1 kg below placebo at 19 weeks.
    • Bleeding; angle-closure glaucoma; sexual dysfunction.

Monitoring & Labs

  • Suicidality: every visit for 3 months, at every dose change in either direction, then every 3 months. Instruct the family in DAILY home observation for the first month
  • Activation and mania: screen for bipolar history before the first dose, then ask about reduced sleep need, pressured speech and elevated mood every 3 months
  • Growth: plot height and weight at baseline, every 3 months for the first year, then every 6 months
  • Hyponatremia: check sodium for new headache, confusion or unsteadiness, or when a diuretic is started
  • Bleeding: ask about bruising and nosebleeds every 3 months; check the INR on warfarin
  • Response: do not judge efficacy before 4 weeks in MDD or 5 weeks in OCD; reassess every 6 months, with sexual function

Discontinuation & Taper

  • Effectively self-tapering: both fluoxetine and norfluoxetine fall gradually at the end of therapy, minimizing discontinuation symptoms.
  • The contrast that drives drug choice: Zoloft has a 26-hour half-life and must be reduced gradually. Where adherence is unreliable, fluoxetine is safer.
  • A gradual reduction is still preferred; reactions include dysphoric mood, irritability, dizziness, electric shock sensations and insomnia. If they follow a decrease, resume the previous dose.
  • Drug holidays are not appropriate; steady state takes 4 to 5 weeks, so a break resets the clock.
  • Interactions outlast the drug: for 5 weeks an MAOI and thioridazine stay contraindicated.

Pregnancy & Lactation

  • Pregnancy: decades of data have not established increased risk of major birth defects or miscarriage.
    • Later exposure may raise the risk of persistent pulmonary hypertension of the newborn; third-trimester exposure has produced respiratory distress, feeding difficulty, hypotonia and irritability.
    • Weigh rather than abstain: women who stopped antidepressants in pregnancy relapsed more often.
  • Lactation: present in human milk; agitation, irritability, poor feeding and poor weight gain reported.
    • Milk levels run HIGHER than most other SSRIs, relative infant dose roughly 2.4% to 7%, with no adverse developmental effects to 5 years (LactMed 2026).
    • Zoloft is the lower-exposure choice when starting an SSRI while nursing.
  • Exposure Registry: National Pregnancy Registry for Antidepressants, 1-844-405-6185, womensmentalhealth.org

Counseling Points

  • Counsel the family on:

    • Nothing much happening for two weeks. Name the review point aloud: 4 weeks for depression, 5 for OCD.
    • Taking it in the morning, and splitting a dose above 20 mg if nausea is the problem.
    • A missed dose being forgiving here, and a dose increase taking weeks to show for the same reason.
    • Never accepting a 90 mg once-weekly capsule; it has never been studied in children.
    • Telling every future prescriber about fluoxetine taken within the last 5 weeks.
    • Daily home observation for the first month for out-of-character behaviour.

  • Advise them to call for:

    • New or worsening talk of self-harm, or any abrupt mood change after a dose change.
    • Days without needing sleep, much faster speech, or a jump in energy.
    • Any rash or hives, particularly with fever or joint swelling.
    • Shivering, twitching, stiffness, racing heart, sweating and confusion together.
    • Nosebleeds that will not stop, unexplained bruising, or black stools.
    • Fainting, irregular heartbeat, or a seizure.

References

  1. DailyMed. Prozac (fluoxetine) capsule. Dista Products Company. 2023. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c88f33ed-6dfb-4c5e-bc01-d8e36dd97299
  2. DailyMed. Fluoxetine delayed release capsule, 90 mg weekly. Dr. Reddy's. 2026. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=887fc670-db67-4cfe-967b-46b38375dae5
  3. LactMed. Fluoxetine. 2026. https://www.ncbi.nlm.nih.gov/books/NBK501186/
  4. AHRQ. Anxiety in children. CER No. 192, 17-EHC023-EF. 2017. https://www.ncbi.nlm.nih.gov/books/NBK476277/
  5. AACAP. Depressive disorders practice guideline. 2023. PMID 36273673. https://www.jaacap.org/article/S0890-8567(22)01852-4/fulltext
  6. FDA. NDC Directory, openFDA, generic name fluoxetine. 2026. https://api.fda.gov/drug/ndc.json?search=generic_name:%22fluoxetine%22&limit=1000
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