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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Escitalopram vs FluoxetineDETAILED OVERVIEW
What is Fluoxetine?
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.
ATC code
N06AB03
Prescription
Prescription only (Rx)
Mechanism
Selective serotonin reuptake inhibitor (SSRI), SERT inhibition
Half-life
4-6 days (parent), norfluoxetine ~16 days
Onset
4-6 weeks (full antidepressant response)
Anecdotal reports describe Fluoxetine (Prozac) as one of the more well-tolerated, long-lasting SSRIs, with a lighter, more energizing subjective profile compared to sedating alternatives. Its ultra-long half-life (4-6 days for active metabolites) is forgiving for missed doses, making it a frequent Rx choice for elderly patients prone to skipping medications. Common early-treatment tradeoffs include activation, insomnia, emotional blunting, and SSRI-class sexual side effects. Community accounts note pro-cognitive properties – preclinical and clinical reports suggest improvements in long-term memory, executive function, attention, and impulsivity, with stronger effects in neurodegenerative contexts. Caution: discontinuation syndrome is milder than shorter-acting SSRIs due to self-tapering, but MAOi combinations are strictly contraindicated (serotonin syndrome risk).
⚠ Not clinical evidence – based on user accounts.
Data console
Lab data
Findling RL, DelBello MP, Zuddas A . Vortioxetine for Major Depressive Disorder in Adolescents: 12-Week Randomized, Placebo-Controlled, Fluoxetine-Referenced, Fixed-Dose Study.. J Am Acad Child Adolesc Psychiatry.
Cipriani A, Furukawa TA, Salanti G et al. . Comparative efficacy of 21 antidepressants for MDD. Lancet. 2018;391(10128):1357-1366..
Tollefson GD, Rampey AH Jr, Potvin JH et al. . Fluoxetine in obsessive-compulsive disorder: pooled-trial efficacy and tolerability. Arch Gen Psychiatry. 1994;51(7):559-67..
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
Vortioxetine for Major Depressive Disorder in Adolescents: 12-Week Randomized, Placebo-Controlled, Fluoxetine-Referenced, Fixed-Dose Study.
Findling RL, DelBello MP, Zuddas A
Comparative efficacy of 21 antidepressants for MDD
Cipriani A, Furukawa TA, Salanti G et al.
Fluoxetine in obsessive-compulsive disorder: pooled-trial efficacy and tolerability
Tollefson GD, Rampey AH Jr, Potvin JH et al.
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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.