Taking the Antidepressant Fluoxetine (Prozac)

Fluoxetine is a drug prescribed to treat depression. It is the active ingredient in brand names like Prozac and Sarafem. In addition to depression, fluoxetine is prescribed to treat obsessive-compulsive disorder, binge eating disorder, some symptoms of bulimia, and panic disorder without agoraphobia. Sarafem specifically is prescribed to treat premenstrual dysphoric disorder.

What Is Fluoxetine?

This generic medication is a selective serotonin reuptake inhibitor, or SSRI. This class of medications controls how the neurotransmitter serotonin is absorbed by receptor cells. When less serotonin is absorbed, communication between neurons is easier and mood improves. Serotonin is one of the neurotransmitters responsible for changes in mood, as well as regulation of the risk/reward system.

Who Makes Fluoxetine, and When Was It Approved?

Prozac and Sarafem are manufactured by Eli Lilly and Company. It is also a key component of Prozac Weekly, a delayed-release version of Prozac, also manufactured by Eli Lilly. The original formula of Prozac was approved by the Food and Drug Administration in 1987. Since then, generic forms of fluoxetine have been approved, and new versions have been released, which help different types of depression or mood disorders.
Further Reading


Generic fluoxetine comes in capsules with 10 mg, 20 mg, or 40 mg dosages. Delayed-release capsules have 90 mg of fluoxetine, but other ingredients help the medication release in a slow, controlled way into the body, so the medication does not hit all at once. A liquid form of fluoxetine is available in 20 mg per 5 mL, and tablets have incremental measures of 10 mg, 20 mg, and 60 mg.

A dose of fluoxetine is typically taken once per day, starting with the lowest possible dose and increasing, with physician or therapist supervision, as necessary. Prozac Weekly can be taken once per week.

No one should take fluoxetine or other prescription medications without the supervision of a medical professional, like a physician or a psychiatrist. Self-dosing can lead to substance abuse and will not help ease depression or other mental health conditions.

What Does Fluoxetine Treat?

Fluoxetine was originally developed to treat major depression. Symptoms of major depression include:

  • Low mood
  • Feeling empty
  • Persistent sadness without cause
  • Feeling numb
  • Loss of interest in daily activities or hobbies
  • Changes in appetite and weight
  • Low energy
  • Difficulty concentrating
  • “Nervous energy,” or feeling very restless
  • Slowed movements or feeling “heavy”
  • Suicidal thoughts or behaviors

This medication treats similar symptoms involving low mood or mood swings around PMDD, bulimia, panic disorder, obsessive-compulsive disorder, chronic depression, or anxiety disorder.

Fluoxetine Side Effects

General side effects associated with fluoxetine include:

  • Unusual or abnormal dreams
  • Anxiety, restlessness, and nervousness
  • Loss of strength or muscle mass
  • Diarrhea
  • Dry mouth
  • Upset stomach or nausea
  • Flu-like symptoms
  • Difficulty falling asleep or getting restful sleep
  • Decreased sex drive
  • Sore throat
  • Rash
  • Sinus swelling
  • Tremors or shaking
  • Flushing of the skin
  • Yawning
  • Sleepiness, drowsiness, or increased need for sleep

Changes in weight are a potential side effect of fluoxetine, as with other SSRIs, and they typically involve weight gain. This could, in part, be due to a lifting of appetite as symptoms of depression are relieved. It could also be due to changes in physical energy that reduce the amount of exercise the person gets.
Side effects that should be immediately reported to a doctor include:

  • New or worsening anxiety
  • Extreme agitation or restlessness
  • Panic attacks
  • Trouble sleeping and insomnia
  • Irritability or aggressiveness that was not present before
  • Obsessing over, or acting on, dangerous impulses
  • Extreme increase in physical energy
  • Dramatically increased talkativeness
  • Decreased need for sleep

These could be signs of serotonin syndrome or potential bipolar disorder that was misdiagnosed as depression. Symptoms of serotonin syndrome include:

  • Hallucinations
  • Dizziness
  • Loss of coordination
  • Ataxia
  • Hypertension

In 2013, the FDA noted that there was an increased risk of abnormal heart rate in people who took fluoxetine. Some people who took this medication developed bradycardia, hypokalemia, and uncompensated heart failure, among other conditions. People with pre-existing heart conditions should consult their doctor before beginning fluoxetine.

One of the most dangerous potential side effects is the potential for increased suicidal thinking. Although fluoxetine should relieve symptoms of depression, including thoughts of worthlessness and death, the opposite experience occurs for some people. It is important to speak with a doctor about this if it does not go away within five weeks of starting a regular dose of the medication.

Overdose from Fluoxetine

Although it is rare, it is possible to overdose on fluoxetine. Symptoms include:

  • Difficulty focusing eyes, or bnormal pupil size
  • Irregular gait
  • Confusion or trouble with attention
  • Unresponsiveness or stupor
  • Tremors or muscle weakness
  • Extreme sleepiness or falling unconscious
  • Intense, abnormal excitement
  • Rapid heartbeat
  • Nausea, vomiting
  • Seizures


People who stop taking fluoxetine suddenly may experience withdrawal symptoms, including:

  • Anxiety
  • Stomach problems
  • Headaches
  • Difficulty with motor functions

For people who wish to discontinue fluoxetine, it is important to speak with a psychiatrist or physician about developing a tapering schedule to reduce the body’s dependence on the medication over time.

Interactions with Other Medications

Like other SSRIs, fluoxetine can interact negatively with other drugs, including other antidepressants and prescription medications.

It is important to avoid taking multiple SSRIs or other antidepressants together. The increase in serotonin can lead to serotonin syndrome. A combination of antidepressants like SSRIs with MAO inhibitors or tricyclic antidepressants can enhance each other’s effects, leading to dangerous side effects.

Other drugs that may interact with fluoxetine include:

  • Lithium
  • Tramadol
  • Methadone
  • Sedatives or tranquilizers
  • Benzodiazepines
  • Some antibiotics
  • Anticoagulants like warfarin
  • Opioid painkillers
  • Antipsychotics
  • Medications to treat migraines
  • Diuretics
  • John’s wort
  • Valerian
  • Tryptophan
  • Anti-seizure medications

It is also important to avoid drinking alcohol while taking fluoxetine, as the medication can enhance the effects of alcohol on the body. Moderate or occasional drinking should not be harmful, although speaking with a doctor about potential side effects is important.

Interactions with Physical Conditions

If a person has physical conditions that affect major organ systems, they may not be able to take fluoxetine safely, or they may have to take a reduced dose. Some conditions that interact with fluoxetine include:

  • Liver failure or cirrhosis
  • Kidney disease or failure
  • Diabetes
  • Glaucoma
  • Epilepsy or other seizure disorders
  • Bipolar disorder
  • Previous history of substance abuse

Women who are pregnant, who wish to become pregnant, or who are breastfeeding should consult a doctor about their condition and fluoxetine. There is very little risk to children of mothers taking this medication, although there is some risk that a baby could be born prematurely if the mother takes fluoxetine through the third trimester of pregnancy. There is also a small risk of heart conditions in babies whose mothers took fluoxetine throughout pregnancy, but the chance is about 1 percent. The drug can also pass through breastmilk and have an effect on the infant. However, the decision to continue or stop fluoxetine ultimately involves a discussion between a new mother and her doctor.

Embracing a Better Future

People who struggle with mood disorders like depression are more likely to struggle with substance abuse. Attempts to self-medicate mental health issues with alcohol or drugs can make depression or anxiety worse in the long-term. Fortunately, rehabilitation programs are able to help people who struggle with co-occurring disorders. It is important to treat both the substance abuse and mental health problem at the same time. With proper care, people can leave substance abuse in the past and embrace a healthy life in recovery.