What Is Prozac (Fluoxetine) Used For?
Prozac is the brand name for fluoxetine, an SSRI antidepressant approved in the US for depression, OCD, panic disorder and bulimia.
By withClaro Editorial · 2026-11-02 · 4 min read
Clinical section reviewed by Dr. Jason Tan, Consultant Psychiatrist, on October 27, 2026.
More about Prozac
Comparisons
Key takeaways
- Prozac is the brand name for fluoxetine, an SSRI approved for depression, OCD, panic disorder and bulimia, and for children with depression from age 8.
- The usual adult dose for depression is 20 mg once a day in the morning, with a maximum of 80 mg.
- Fluoxetine stays in the body far longer than other SSRIs, so dose changes take weeks to show fully.
- Prozac isn't a controlled substance, and stopping should still be gradual, planned with your prescriber.
Prozac is used for depression, obsessive compulsive disorder (OCD), panic disorder and bulimia. It is the brand name of fluoxetine, an antidepressant of the SSRI class, and the third most prescribed SSRI in the US after sertraline and escitalopram: about 29.5 million prescriptions in 2024, by ClinCalc estimates.
What is Prozac used for?
The FDA label approves Prozac for four conditions:
| Condition | From age | Starting dose in the label |
|---|
| Depression | 8 | 20 mg for adults |
| OCD | 7 | 20 mg for adults |
| Panic disorder | adults | 10 mg for a week, then 20 mg |
| Bulimia | adults | 60 mg |
Two more uses are approved in combination: with olanzapine, it is also approved for depression in bipolar I disorder and for depression that has not responded to two other antidepressants. The NHS adds that it is sometimes used for menopause symptoms.
How does Prozac work?
Medically reviewed by Dr. Jason Tan on October 27, 2026, this section only.
Fluoxetine blocks the reuptake of serotonin, so more of it stays available between nerve cells. The label says the full effect may take 4 weeks or longer for depression and 5 weeks or longer for OCD. The clinical view:
Antidepressants change how the brain uses chemical messengers, but how this lifts mood is not fully understood.
The chemical change starts within hours, yet the full effect on mood takes weeks. Current thinking points to early changes in how the brain processes emotion, then slower changes in receptors, in brain circuits that handle emotion, and in how the brain forms new connections.
The idea that depression comes from a shortage of serotonin is now considered too simple. That leaves the mechanism unclear, as with many effective medicines. Trials show antidepressants help more than placebo, with the clearest benefit in moderate to severe depression. ## How well does Prozac work compared with other antidepressants?
A 2018 review in The Lancet of 522 trials in adults with depression found all 21 antidepressants it studied more effective than placebo. Fluoxetine was among the better tolerated, one of only two with fewer dropouts than placebo, but among the four least effective in head-to-head trials. The differences between drugs were small and the evidence for many comparisons was moderate to very low. That review covered short-term depression treatment only, not OCD, panic disorder or bulimia.
What side effects does Prozac cause?
In the depression trials, the most common side effects were nausea, 21% against 9% on placebo, insomnia, 16% against 9%, nervousness, 14% against 9%, and sleepiness, 13% against 6%; decreased appetite, diarrhea, dry mouth, tremor, sweating, yawning and sexual side effects were also on the label's list. The NHS says some ease after a couple of weeks, but some can last longer. Like every US antidepressant, Prozac carries an FDA boxed warning about suicidal thoughts in people 24 and younger, and it asks that people of any age be watched closely when they start, especially in the first weeks and after a dose change. If you're having thoughts of harming yourself, contact emergency services or a crisis line straight away. In the US, call or text 988. In the UK, call Samaritans on 116 123. Elsewhere, find a crisis line near you.
What doses does Prozac come in?
Prozac capsules come in 10 mg, 20 mg and 40 mg. For depression in adults, the label starts at 20 mg once a day in the morning and allows up to 80 mg. In the label's trials comparing 20, 40 and 60 mg, 20 mg was enough for most people with depression, and the dose is then adjusted to you. Panic disorder starts at 10 mg for a week, then goes to 20 mg, and bulimia uses 60 mg. More in Prozac dosage.
How long does Prozac stay in your system?
Longer than any other SSRI. Fluoxetine has a half-life of 1 to 3 days after a single dose and 4 to 6 days with daily use, and its active breakdown product, norfluoxetine, lasts 4 to 16 days. Steady levels take 4 to 5 weeks to build, so a dose change takes weeks to show fully. After the last dose, it stays active for weeks: the label asks for a 5-week gap before starting an MAOI antidepressant, which is the clearest guide to how long it lingers.
That long tail can soften stopping, but the NHS says not to stop suddenly, because it may cause withdrawal symptoms; your doctor will lower the dose over weeks or months. More in Prozac withdrawal.
What is the generic name for Prozac?
The generic name is fluoxetine, and pharmacy labels often say fluoxetine hydrochloride. The FDA first approved Prozac on December 29, 1987. Generic fluoxetine contains the same active ingredient at the same strength.
What drug class is Prozac?
Prozac is a selective serotonin reuptake inhibitor, or SSRI, the same class as Zoloft and Lexapro. The FDA label does not list it as a controlled substance. The NHS says SSRIs are usually prescribed first, because their side effects are generally easier to manage.
For the other types of antidepressant, see the list of antidepressants.
What should you tell your prescriber before starting Prozac?
Some conditions and medications change how Prozac is used, so it is worth naming them at the first appointment. Before you start, tell your prescriber about:
- other antidepressants you have taken and how they went
- other medications, especially blood thinners, migraine triptans and St John's wort
- heart rhythm problems, liver problems, seizures or a history of mania
- pregnancy, plans for pregnancy or breastfeeding; don't stop Prozac on your own if you become pregnant
Download on the App Store Prozac takes weeks to settle, and its effects on sleep, energy and mood change along the way. The withClaro app lets you log mood, sleep, energy and side effects each day, linked to your dose, and turns it into a report for your prescriber.
Related articles
Sources
- ClinCalc DrugStats: The Top 300 Drugs of 2024
- PROZAC (fluoxetine) prescribing information, US Food and Drug Administration via DailyMed
- NHS: Fluoxetine
- Cipriani et al., 2018, The Lancet: Comparative efficacy and acceptability of 21 antidepressant drugs
- Drugs@FDA: Prozac, application 018936
- Royal College of Psychiatrists: Antidepressants
- NHS: Antidepressants, overview and types
Claro articles are for self-monitoring and educational purposes only. They are not a medical device, therapist, or diagnostic tool, and do not replace care from your prescribing clinician. If you are in crisis, contact your care team, emergency services, the Samaritans (UK: 116 123), or the Crisis Text Line (US: text HOME to 741741).