What Is Prozac? Uses, Side Effects, and What To Know About Prozac and Anxiety

By: Patricia Weiser, PharmD

Prozac (generic name: fluoxetine) is a prescription antidepressant in a group of medications called selective serotonin reuptake inhibitors (SSRIs). Fluoxetine is used to treat depression, obsessive-compulsive disorder (OCD), panic disorder and certain other conditions. 

If you’re considering fluoxetine, a health care provider can help you understand what it may treat, how long it may take to work, possible side effects and whether it fits into your treatment plan.

What is Prozac?

Prozac is a brand name for fluoxetine. Generic fluoxetine is also available. A generic medication contains the same active ingredient as the brand-name version and is designed to work the same way in the body.

Fluoxetine belongs to a class of antidepressants called SSRIs. These medications are thought to work by increasing serotonin signaling in the brain. Serotonin is a chemical messenger that nerve cells use to communicate and plays a role in mood and other body functions.

Fluoxetine requires a prescription. It should be used only under the guidance of a qualified medical professional who can consider your symptoms, medical history, other medications and possible side effects.

How to take Prozac

Fluoxetine is taken by mouth and is available in several forms, including capsules, tablets, liquid and a delayed-release capsule.

Daily doses of fluoxetine can vary depending on the condition being treated, generally ranging from 10 mg to 80 mg per day. It is usually taken once daily in the morning, with or without food. A prescriber may adjust your dose over time based on how well the medication is working for you. A once-weekly 90 mg delayed-release capsule is also an option for certain patients.

What is Prozac used for?

Prozac has several FDA-approved uses:

Fluoxetine by itself is not FDA-approved for depressive episodes associated with bipolar I disorder or treatment-resistant depression. For these uses, fluoxetine is combined with another medication called olanzapine.

Premenstrual dysphoric disorder (PMDD) is another FDA-approved use of fluoxetine. This use was approved under the brand name Sarafem, which is now available as a generic medication.

Can Prozac be used for anxiety?

Yes, fluoxetine may sometimes be prescribed for anxiety-related symptoms or conditions. For example, fluoxetine is FDA approved  to treat panic disorder, and may be prescribed off label for certain other anxiety disorders, such as social anxiety disorder. . 

Fluoxetine is separately FDA-approved for premenstrual dysphoric disorder (PMDD), which may include symptoms such as anxiety or tension. An off-label use means a medication is being prescribed for a condition it isn’t specifically FDA-approved to treat. This is fairly common and doesn’t mean the medication itself is unapproved.

If you’re curious about prozac and how it may help if you’re experiencing anxiety, it’s best to reach out to your healthcare provider or schedule an appointment with a psychiatrist or psychiatric provider. 

BetterHelp has an online psychiatry platform that allows you to connect with a psychiatrist within a few days and no referral is required. BetterHelp accepts insurance and works with most major insurer plans. 

*Based on finalized paid psychiatry visits with a copay. Insurance availability, coverage, and costs vary by state, plan, provider network, and provider availability.

How does Prozac work?

As an SSRI, fluoxetine works mainly by changing how the brain handles serotonin. Normally, serotonin is released between nerve cells and then taken back up by the cell that released it. This process is called reuptake.

Fluoxetine blocks some of that reuptake. As a result, serotonin stays available between nerve cells longer, increasing serotonin signaling. The initial effect on serotonin happens relatively quickly, but the changes that lead to symptom and mood improvement take more time.

How long does Prozac take to work?

Fluoxetine doesn’t provide its full benefit right away. An initial antidepressant effect may begin within about two to four weeks, while the full benefit may take four to five weeks or longer. The timeline can also vary depending on the condition being treated and the individual.

You may notice some changes before the medication reaches its full effect. Early results alone don’t necessarily show how well fluoxetine will ultimately work, so changes in treatment should be discussed with a healthcare provider rather than made on your own.

Common Prozac side effects

Not everyone experiences side effects from fluoxetine. Some early side effects may also lessen over time as your body adjusts.

Common side effects may include:

• Nausea
• Diarrhea or indigestion
• Dry mouth
• Trouble sleeping
• Drowsiness or tiredness
• Anxiety or nervousness
• Sweating more than usual
• Tremor or shaking
• Changes in appetite or weight
• Sexual side effects, such as changes in sex drive or erectile dysfunction
• Unusual dreams
• Yawning

Fluoxetine can also cause serious side effects, although these are less common. Examples include serotonin syndrome, seizures, serious allergic reactions, unusual bleeding, low sodium levels, mania or hypomania and changes in the heart’s electrical activity.

Fluoxetine also carries a boxed warning about an increased risk of suicidal thoughts and behaviors in children, adolescents and young adults taking antidepressants. New or worsening symptoms should be taken seriously and discussed promptly with a health care professional.

If you have thoughts of suicide, contact the 988 Suicide & Crisis Lifeline at 988.

How does Prozac make you feel?

There isn’t one specific way fluoxetine makes everyone feel. Many people feel the same at first, as symptoms of the condition being treated may take several weeks to improve.

Fluoxetine can be somewhat activating, and some people experience nervousness, anxiety, agitation or trouble sleeping, particularly early in treatment or after a dose increase, while other people may feel tired or drowsy from fluoxetine. Many side effects that occur early in treatment lessen with time, but experiences vary.

When to talk to a healthcare professional?

Before taking fluoxetine, make sure your prescriber and pharmacist know about the other prescription medicines, over-the-counter products and supplements you use. Fluoxetine can interact with several medications, including some that affect serotonin, bleeding risk or heart rhythm. It’s also important to discuss relevant health conditions and whether you are pregnant, planning a pregnancy or breastfeeding.

Contact a health care professional if side effects are severe, concerning or don’t improve. Seek prompt medical attention for symptoms that could indicate a serious reaction, such as trouble breathing or swelling, seizures, fainting or an irregular heartbeat, unusual bleeding or symptoms of serotonin syndrome.

You should also check with a prescriber before stopping fluoxetine or changing your dose. Stopping suddenly can cause symptoms such as mood changes, irritability, dizziness, anxiety, sweating, headache, tiredness or sleep problems.

This article is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Medication decisions should be made with a licensed healthcare professional who can consider your individual symptoms, health history, current medications, and treatment goals. Do not start, stop, or change any medication without guidance from a qualified healthcare professional. If you are experiencing a medical emergency or symptoms that feel urgent or life-threatening, call emergency services or seek immediate medical care.