Fluoxetine (Prozac) 101: What You Need to Know

Mary Lucas, RN

Medically reviewed by Mary Lucas, RN

Written by Our Editorial Team

Last updated 10/14/2020

Clinical depression is more than just being a little sad. It’s a mental illness that can make it difficult to get out of bed or participate in things you once thought were fun. 

Left untreated, depression can carry you down a dark path.

Though it can be hard to ask for help, knowing you are not alone is some comfort. An estimated 16.1 million Americans suffer from major depressive disorder, just one kind of depression. 

It’s a relatively common issue, and there are solutions available to help fight it. 

TL;DR: What You Need to Know About Fluoxetine

  • Fluoxetine (Prozac®) is an antidepressant approved to treat depression, obsessive compulsive disorder, panic disorder and bulimia. 

  • It’s one of several drugs known as selective serotonin reuptake inhibitors, or SSRIs. 

  • Fluoxetine may interact with other medications you’re on — with serious health implications — so tell your doctor about all drugs you’re taking before starting fluoxetine. 

  • The list of potential fluoxetine side effects is long, but many go away as your body gets used to the medication. 

  • It may take several weeks to see results from taking fluoxetine. 

  • Do not stop fluoxetine abruptly, or you may suffer withdrawal symptoms. 

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What Is Fluoxetine?

Fluoxetine is an antidepressant medication used to treat multiple mental health conditions. It’s also known by several different  brand names, including Prozac

It’s approved by the Food and Drug Administration (FDA) to treat major depressive disorder, panic disorder, obsessive compulsive disorder and the eating disorder bulimia nervosa. 

It’s also sometimes prescribed off-label in the treatment of posttraumatic stress disorder, dysthymia (a milder form of depression) and body dysmorphic disorder.  

Fluoxetine, and Prozac specifically, was the first antidepressant of its class approved for use by the FDA. It’s one of several drugs in the medication class known as selective serotonin reuptake inhibitors, or SSRIs.

How Does Fluoxetine Work? 

SSRIs work by blocking the reabsorption of serotonin, a neurotransmitter, into neurons. This leaves more serotonin circulating freely in your brain. 

Serotonin is crucial in mood regulation and behavior, affecting everything from emotion to memory and sexuality

Other drugs in the SSRI class include: sertraline (Zoloft®), citalopram (Celexa®), paroxetine (Paxil®), and escitalopram (Lexapro®) — all approved by the FDA to treat depression and other mental health disorders.

Fluoxetine comes in tablets, capsules, delayed-release capsules and liquid. 

Prozac tablets and capsules are generally taken once or twice per day, at the same time each day, while the delayed-released capsules are taken once a week.

Other brands may have different administration regimens, so always follow your healthcare provider’s instructions on when and how to take the medication. 

As with most SSRIs, your healthcare provider may start you out at a small dose, and slowly increase the amount you take to lessen the risk of short-term side effects.

It can take weeks to feel the full benefits of fluoxetine. Once you begin to feel relief from your symptoms, it’s important to continue taking the medication. 

Stopping it may result not only in a return of your original symptoms, but also withdrawal symptoms such as mood changes, dizziness, agitation and irritability, anxiety, sweating, confusion, headache, tiredness and trouble sleeping.

Who Is Fluoxetine For? 

Fluoxetine is for people who have been diagnosed with the conditions it’s been approved to treat. 

However, people experiencing symptoms of major depressive disorder or panic disorder may have yet to receive a diagnosis. The first step to receiving help — whether from an SSRI like fluoxetine or something else — is talking with a healthcare professional. 

Fluoxetine may not be right for people taking certain other prescription drugs. 

The list of medications that may interact negatively with fluoxetine is long, but includes monoamine oxidase inhibitors (MAO inhibitors), fentanyl, lithium, some migraine medications, the supplement St. John’s wort and others. 

The adverse effects from medication interactions can be serious, so it’s important to tell your healthcare provider about all other medicines you take before beginning with fluoxetine.

Children, adolescents and young adults may also want to weigh the risks of fluoxetine heavily. Clinical studies have shown people up to the age of 24 may experience increased suicidal thoughts and tendencies while taking antidepressants like this. 

Those people in particular will want to check in with their healthcare provider frequently if they decide the potential benefits of fluoxetine are worth the risks.

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Fluoxetine Side Effects 

As with any prescription drug, fluoxetine comes with a list of possible side effects. Some of these effects of fluoxetine may dissipate as your body gets accustomed to the medication. 

Common side effects of fluoxetine include abnormal dreams, abnormal ejaculation, flu syndrome, anxiety, asthenia, diarrhea, dry mouth, anorexia, dyspepsia, impotence, insomnia, libido decreased, pharyngitis, nausea, nervousness, rash, tremor, sinusitis (sinus infection), somnolence (drowsiness), sweating, vasodilatation and yawning.

More serious side effects can occur with fluoxetine.

If you experience any of the following, or other concerning effects, contact your healthcare provider immediately: restlessness, hives or rash, chills or fever, joint and muscle pain, cold sweats, confusion, sweating, thirst, behavior changes, racing heart rate, convulsions, dry mouth and excessive thirst, drowsiness, difficulty concentrating, manic behavior, trouble breathing, unusual body or facial movements, unusual weakness, or shivering and shaking.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.