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This is an information resource — not medical advice.

PillCodex provides general educational information about medications. This content is not a substitute for professional medical advice, diagnosis, or treatment. Never start, stop, or change a medication based on what you read here. Always speak to your doctor, pharmacist, or qualified healthcare provider with questions about your medications.

🚨 If you are experiencing a medical emergency or think you may have taken too much of a medication, call emergency services (911 in the US) or go to your nearest emergency room immediately.

SSRI (Selective Serotonin Reuptake Inhibitor)🔒 Prescription only

What Is Fluoxetine (Prozac) Used For?

Brand names: Prozac, Sarafem

Fluoxetine (Prozac) was the first widely-used SSRI and remains one of the most prescribed antidepressants in the world. It has the longest half-life of all SSRIs.

What is Fluoxetine used for?

  • Major depressive disorder
  • OCD (obsessive-compulsive disorder)
  • Panic disorder
  • Bulimia nervosa
  • Premenstrual dysphoric disorder (PMDD)
  • Bipolar depression (combined with olanzapine)

How does Fluoxetine work?

Fluoxetine blocks the reuptake of serotonin into neurons after it is released, increasing the amount of serotonin available in the brain. More serotonin improves communication between brain cells associated with mood regulation.

Dosage information

💊Available forms
  • 10mg capsules
  • 20mg capsules
  • 40mg capsules
  • 60mg capsules
  • 20mg/5ml liquid
  • +1 more
📏Typical dosage

Usually started at 20mg once daily in the morning. May be increased to 40–60mg. Taken in the morning as it can cause insomnia. Takes 4–8 weeks for full effect.

⚠️ Dosage varies by individual. Always follow your doctor's or pharmacist's instructions — never self-dose based on general information.

Side effects

Common

  • Insomnia (especially if taken at night)
  • Nausea (usually improves after 1–2 weeks)
  • Headache
  • Dry mouth
  • Decreased appetite
  • Sexual side effects
  • Sweating
  • Anxiety at start of treatment

⚠️ Serious — contact your doctor

  • Increased suicidal thoughts in those under 25 (black box warning)
  • Serotonin syndrome when combined with other serotonergic drugs
  • Bleeding risk
  • Mania in patients with undiagnosed bipolar disorder
  • QT prolongation at high doses

Important warnings

Black box warning: monitor for suicidal thoughts especially in young people in first weeks
Always take in the morning — can cause significant insomnia if taken at night
Do NOT combine with MAO inhibitors — wait at least 14 days after stopping fluoxetine before starting an MAOI (fluoxetine stays in the body for weeks)
Causes significantly more drug interactions than other SSRIs due to enzyme inhibition

Drug interactions

These substances may interact with Fluoxetine. This is not a complete list — always tell your doctor and pharmacist ALL medications and supplements you take.

MAO inhibitors (very dangerous, long washout needed)Thioridazine and pimozide (contraindicated — heart rhythm)Tramadol and triptans (serotonin syndrome)Many medications metabolised by CYP2D6 (fluoxetine is a strong inhibitor)WarfarinNSAIDs

Pregnancy & breastfeeding

🤰 Use with caution — discuss risks and benefits carefully with your doctor

Always consult your doctor or obstetrician before taking any medication during pregnancy or while breastfeeding.

Frequently asked questions

What is fluoxetine (Prozac) used for?

Fluoxetine treats major depression, OCD, panic disorder, bulimia nervosa, and PMDD. It is one of the most studied antidepressants in the world.

How long does fluoxetine stay in your system?

Fluoxetine has an exceptionally long half-life of 1–6 days, and its active metabolite lasts 4–16 days. It can take 4–6 weeks to fully leave the system after stopping — this is why discontinuation syndrome is milder than other SSRIs.

Why should I take fluoxetine in the morning?

Fluoxetine is stimulating compared to other antidepressants and commonly causes insomnia if taken at night. Taking it in the morning significantly reduces this problem.

Does fluoxetine cause weight gain?

Short-term, fluoxetine often reduces appetite and may cause slight weight loss. Long-term use can cause modest weight gain in some people, though it tends to be less than other antidepressants.

Can I stop fluoxetine suddenly?

Fluoxetine's long half-life means discontinuation syndrome is much milder than with other SSRIs. However, still taper gradually under your doctor's guidance to minimise any symptoms.

Related medications

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This is an information resource — not medical advice.

PillCodex provides general educational information about medications. This content is not a substitute for professional medical advice, diagnosis, or treatment. Never start, stop, or change a medication based on what you read here. Always speak to your doctor, pharmacist, or qualified healthcare provider with questions about your medications.

🚨 If you are experiencing a medical emergency or think you may have taken too much of a medication, call emergency services (911 in the US) or go to your nearest emergency room immediately.

Information on this page is sourced from general pharmaceutical references and is provided for educational purposes only. Drug information may change — always verify with your pharmacist or prescriber. PillCodex.com is not affiliated with any pharmaceutical company.