Fluoxetine

PROZAC

Open Fluoxetine in the interactive console ↗

Pronunciation: floo-OX-e-teen (PROE-zak)

Fluoxetine ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Fluoxetine ballicule

Fluoxetine PROZAC mascot mnemonic cartoon — Visual mnemonic: Fluoxetine mascot
**“Prolonged sack of Flustered ox”**
Fluffer inHibitor (fluoxetine, fluvoxamine, fluconazole)
#20 → 20 mg usual starting dose

What it isSerotonin reuptake inhibitor with 5-HT2C antagonism; depression, OCD, bulimia, panic disorder and PMDD.

Why this oneLong persistence makes missed doses and discontinuation easier, but delayed interaction washout is the price.

What limits itActivation, insomnia and sexual dysfunction often limit it. CYP2D6 inhibition compromises tamoxifen; allow the extended MAOI washout.

Fluoxetine molecular structure (skeletal formula) — Molecular structure: Fluoxetine

FDA-approved for

depression (1987)
OCD (1994)
bulimia nervosa (1994)
panic disorder (2000)
PMDD (2000)

Off-label

premature ejaculation
fibromyalgia

FDA label

Read the full label on DailyMed ↗

BOXED WARNING Increased risk of suicidal thoughts and behaviors in children, adolescents, and young adults.

FDA dosing	Population	Start	Target	Max
Major depressive disorder	Adults	20 mg QD (AM)	20 mg QD	80 mg/day
Major depressive disorder	Peds (children/adolescents)	10–20 mg QD	20 mg QD	20 mg QD
Obsessive compulsive disorder	Adults	20 mg QD (AM)	20–60 mg/day	80 mg/day
Obsessive compulsive disorder	Peds (children/adolescents)	10 mg QD	20–60 mg/day	60 mg/day
Bulimia nervosa	Adults	60 mg QD (AM)	60 mg QD	60 mg/day
Panic disorder	Adults	10 mg QD, then 20 mg QD after 1 week	20 mg/day	60 mg/day
Bipolar I depression (with oral olanzapine)	Adults	20 mg fluoxetine + 5 mg olanzapine QHS	fluoxetine 20–50 mg + olanzapine 5–12.5 mg	75 mg fluoxetine / 18 mg olanzapine (safety limit)
Bipolar I depression (with oral olanzapine)	Peds 10–17y	20 mg fluoxetine + 2.5 mg olanzapine QHS	per efficacy/tolerability	50 mg fluoxetine / 12 mg olanzapine (safety limit)
Treatment-resistant depression (with oral olanzapine)	Adults	20 mg fluoxetine + 5 mg olanzapine QHS	fluoxetine 20–50 mg + olanzapine 5–20 mg	75 mg fluoxetine / 18 mg olanzapine (safety limit)

Titration Increase after several weeks if response inadequate (pediatric MDD: after 1 week at 10 mg; pediatric OCD: after 2 weeks)

Renal Undefined

Hepatic Use a lower or less frequent dose (e.g., in cirrhosis)

Instructions

Administer in the morning; doses >20 mg/day may be given once in AM or split (morning and noon)
When combined with olanzapine, dose once daily in the evening
Taper rather than stop abruptly to reduce discontinuation symptoms
Do not use an MAOI within 14 days before, or for 5 weeks after, fluoxetine

Available strengths

cap 10, 20, 40 mg
tab 10, 20, 60 mg

Contraindications

MAOIs (concurrently or within 14 days of stopping MAOI); allow 5 weeks after stopping fluoxetine before starting an MAOI due to risk of serotonin syndrome
Pimozide (QT prolongation; fluoxetine raises pimozide levels via CYP2D6)
Thioridazine (QT prolongation; do not use within 5 weeks of stopping fluoxetine)

Cautions

Serotonin syndrome
Suicidal thoughts and behaviors
Allergic reactions and rash
Activation of mania/hypomania; screen for bipolar disorder
Seizures
Altered appetite and weight
Increased risk of bleeding (with NSAIDs/aspirin/warfarin)
Angle-closure glaucoma
Hyponatremia / SIADH
QT prolongation
Long half-life — dose changes take weeks to reflect in plasma
Sexual dysfunction

Adverse reactions

Nausea
Insomnia
Headache
Anxiety
Nervousness
Somnolence
Tremor
Diarrhea
Anorexia
Dry mouth
Asthenia
Decreased libido
Sweating

Pregnancy Published data have not established an increased risk of major birth defects or miscarriage; possible increased postpartum hemorrhage and poor neonatal adaptation/PPHN with third-trimester exposure.

Lactation Fluoxetine and norfluoxetine present in human milk; monitor the infant for agitation, irritability, poor feeding, and poor weight gain.

Cost

Fluoxetine (PROZAC)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $/mo	CostPlus
10 mg	tab	30 qd	$2.09	offered
20 mg	tab	30 qd	$2.51	offered
60 mg	tab	30 qd	$5.45	offered
10 mg	cap	30 qd	$1.06	offered
20 mg	cap	30 qd	$0.88	offered
40 mg	cap	30 qd	$1.56	offered

Available combined with: olanzapine / fluoxetine

Generic entry2001

⚠ BOXED WARNING

Suicidal thoughts and behaviors in patients under 25

Classes and tags

Clinical profile

Therapeutic safety burden2 / 4

Overdose danger2 / 4

Weight-gain liability1 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryC

Defining liabilityLong half-life and CYP2D6 inhibition create persistent interactions; activation and serotonin toxicity are possible.

Serotonin and MAOI

Provisional washout figures

SRI significance3 / 4

MAO-A inhibition0 / 4

Serotonin release0 / 4

Elevating mechanismSRI

Non-elevating actionNone recorded

Exposure dependenceTherapeutic exposure; severe toxicity requires meaningful MAO-A inhibition

Washout BEFORE an MAOI35 days

Evidence confidenceHigh

InterpretationClinically significant SRI; norfluoxetine requires a prolonged washout before an MAOI. A second SRI generally represents therapeutic duplication/additive adverse effects, not the classic life-threatening interaction.