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Prozac (fluoxetine)

Profile and Side Effects of Prozac (fluoxetine)


Updated July 16, 2014

Prozac is the world's most widely prescribed antidepressant; it has been used by more than 35 million people worldwide.
Paul S. Howell/Contributor/Hulton Archive/Getty Images


General Information

What are the side effects of Prozac? How long does it take to work? Is it addictive? If you have been prescribed Prozac, you may be wondering about the side effects, benefits and risks of taking this medication.

Prozac (fluoxetine) is an SSRI antidepressant manufactured by Eli Lilly. In 1987, Prozac was the first SSRI to enter the U.S. market as an approved treatment for depression. Fluoxetine is indicated for the treatment of:


Dosage Information

Prozac and its generic equivalent, fluoxetine, is manufactured in scored tablets and capsules of 10, 20 and 40 mg. It is also available in a liquid oral solution. Your doctor may begin therapy with a low dose that may be increased if your symptoms do not improve. Starting at a low dose can also minimize some of these side effects, because it gives your body time to adjust to the medication. Prozac (fluoxetine) is usually taken once daily and may be taken with food if stomach upset occurs.

Prozac Weekly is an extended-release medication that works by taking a weekly single dose that processes in the body over a seven-day period. Prozac Weekly is manufactured in a 90 mg capsule.

Side Effects of Prozac

Some of the common side effects associated with Prozac (fluoxetine) therapy include:

  • anxiety
  • headache
  • nausea
  • diarrhea
  • drowsiness
  • insomnia
  • decreased appetite
  • increased sweating
  • decreased sexual drive
  • ejaculatory and orgasmic delay or impairment

Some people experience a reduction in some of these side effects after being on the medication for a while. If they remain bothersome, though, you should consult with your doctor.

If you experience any of the following less common side effects, you should call your doctor right away:

  • agitation or irritability
  • restlessness
  • impulsiveness
  • hyperactivity
  • tremors
  • rash

You should get emergency medical attention if you experience any of the following rare, but serious, side effects:

  • Allergic reaction - difficulty breathing; swelling of your face, lips or tongue or difficulty swallowing.
  • Seizures
  • Problems with balance or coordination
  • Suicidal thoughts

These are not the only side effects that may be experienced with fluoxetine. You should report any bothersome side effects to your doctor or other healthcare professional.

How Long Does Prozac Take to Work?

Some people experience some improvement of symptoms within two or three weeks of starting Prozac. Full therapeutic effect, however, is generally achieved in about 8 weeks.

Is Prozac Addictive?

Prozac is not believed to be addictive or habit-forming.

What if I Miss a Dose?

Take the missed dose as soon as you remember unless it’s nearly time to take your next dose. Do not take extra Prozac to make up the missed dose.

Precautions and Contraindications

Pregnancy. There is evidence that taking Prozac during the third trimester of pregnancy may increase your baby’s risk of developing persistent pulmonary hypertension, a serious and potentially fatal lung disorder. If you are nursing or are pregnant, it is best to discuss the risks and benefits of Prozac therapy with your doctor.

NSAIDs or Aspirin. Use of Prozac with NSAIDs or aspirin may be associated with an increased risk of bleeding.

Liver Disease. Before taking Prozac, tell your doctor if you have impaired liver function. Depending on your condition, your doctor may need to adjust your dose and perform certain tests while on Prozac therapy.

Alcohol. Drinking alcohol with Prozac should be avoided.

This list is not all-inclusive. There are other drug interactions that should be avoided and medical issues your doctor may need to consider. Be sure to tell your doctor about all medications, including over-the-counter drugs and supplements, you are taking before beginning fluoxetine.

Serotonin Syndrome

Any SSRI antidepressant has a risk of producing a potentially life-threatening condition called "serotonin syndrome." This rare condition is usually the result of an interaction of two or more drugs that affect brain serotonin levels. Even some over-the-counter supplements, such as St. John’s Wort, can result in serotonin syndrome if mixed with SSRIs.

A particularly troublesome interaction is mixing SSRIs with a class of antidepressants called "monoamine oxidase inhibitors" (MAOIs), which should not be taken with SSRIs. It is recommended waiting two weeks before beginning any SSRI after stopping MAOI therapy. Prozac has a long elimination half life, and your doctor may advise you to wait a minimum of 5 weeks before beginning an MAOI after discontinuing Prozac.

SSRI Discontinuation Syndrome

Before discontinuing Prozac, talk with your doctor. Some people have reported withdrawal-like symptoms when decreasing or stopping SSRI therapy. It is believed that these symptoms are the result of the brain trying to stabilize serotonin levels after an abrupt change.

Symptoms that may occur during discontinuation of any SSRI therapy include:

  • Nausea
  • Headache
  • Muscle aches
  • Dizziness
  • Electric shock-like sensations in the neck and head

While all of these symptoms are not believed to be dangerous, they can be quite disconcerting. When discontinuing an SSRI, your doctor may give you a gradual reduction schedule to avoid these withdrawal-like symptoms.

FDA Black Box Warning

The association of increased suicidal thoughts, especially among adolescents, with SSRI treatment has been a center of attention and controversy in recent years. In response to the concerns suggested in case studies and some research, the U.S. Food and Drug Administration (FDA) issued a statement in 2007. The FDA proposed that makers of all antidepressant medications indicate a warning on their products about a possible increased risk of suicidal thinking and behavior in young adults, ages 18 to 24, during initial treatment.


Antidepressant Use in Children, Adolescents, and Adults. Revisions to Product Labeling. U.S. Food and Drug Administration. May 2, 2007.

RxList. Zoloft. 09 Oct 2008.

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