ApprovedFDA approvedATC · N06AB03Rx · Prescription only (Rx)

Fluoxetine

The first SSRI (Eli Lilly Prozac, FDA 1987). Ultra-long half-life (4-6 days), FDA-approved for pediatric MDD.

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Fluoxetine vial

WHAT IS FLUOXETINE?

Detailed overview

Fluoxetine is the SSRI-class pioneer (Eli Lilly Prozac, FDA 1987), the first clinically successful serotonin-selective drug. Ultra-long PK (parent 4-6 days, active metabolite norfluoxetine 4-16 days) means slow steady-state (4-5 weeks) but milder discontinuation syndrome (auto-taper). The ONLY SSRI with FDA approval for PEDIATRIC MDD (age 8+), plus OCD and bulimia nervosa. Stark 2003 (PMID 14692046) trial documented pediatric MDD efficacy. Generic, affordable. Strong CYP2D6 inhibitor causing clinically significant interactions.

Data console

Lab data

/lab/molecular-data.jsonLIVE
> ATC codeN06AB03
> PrescriptionPrescription only (Rx)
> MechanismSelective SERT inhibition. Moderate 5-HT2C antagonism (may …
> Half-life4-6 days (parent); norfluoxetine 4-16 days
> Onset4-6 weeks (full antidepressant response)
> BioavailabilityNot characterized as absolute (no IV formulation); 60-80% relative to oral solution – FDA Prozac label

Safety

Side effects, stop signs, contraindications

Side effects · 7

  • Serotonin syndrome (potentially life-threatening): agitation, hyperthermia, myoclonus, hyperreflexia, diarrhea – risk increases with MAOIs, triptans, tramadol, or other serotonergic agents.
  • FDA boxed warning: increased suicidal thoughts and behavior in children, adolescents, and young adults (<25), especially in the first weeks of treatment and at dose changes – close monitoring required.
  • GI and activating effects: nausea, diarrhea, anorexia (tends toward weight loss), plus insomnia and nervousness, which are more common with fluoxetine than other SSRIs (dose in the morning).
  • Sexual dysfunction (15-30%): decreased libido, delayed ejaculation/orgasm, anorgasmia – common, often persistent, and a frequent reason for poor adherence.
  • Induction of mania or hypomania in patients with unrecognized bipolar disorder – screening for bipolarity is advised before starting.
  • Hyponatremia / SIADH (mainly in the elderly and with diuretics) and increased bleeding tendency (impaired platelet serotonin), especially with NSAIDs, aspirin, or anticoagulants.
  • QT prolongation (dose-dependent) and rare seizures at high doses; discontinuation syndrome that, due to the 4-6 day half-life, is milder and later-onset than with short-acting SSRIs.

Contraindications · 2

  • MAOi within 14 days (or 5 weeks after fluoxetine stop – due to long half-life)
  • Concurrent pimozide, thioridazine

Related Pharmaceuticals

Same therapeutic category

Studies

Related research and clinical findings

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Have a question about Fluoxetine?

Educational drug info from official sources (PubMed, FDA, EMA). Does NOT replace medical consultation or the SmPC. Talk to your doctor!

MolekulaX Editorial Team·Source-verified · PubMed · FDA · EMA
Updated: June 19, 2026

The information here is for educational and scientific purposes only. Medication use requires medical consultation and a prescription. The indications, dose ranges, and side effects listed here do NOT replace the official Summary of Product Characteristics (SmPC) or consultation with a physician. Do not start or stop any medication on your own. In an emergency, call your local emergency number.