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Fluoxetine Patient Tips

How it works

Experts believe fluoxetine's effects are due to its ability to block the uptake of serotonin by nerves, leading to an increase in serotonin concentrations in the nerve synapse (space between two nerves). Its activity against other neurotransmitters is much less potent than other antidepressants. Fluoxetine belongs to a group of medicines called Selective Serotonin Reuptake Inhibitors (SSRIs).


Used in the treatment of depression, obsessive-compulsive disorder, bulimia and premenstrual dysphoric disorder (PMDD).


If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • As with other antidepressants, fluoxetine may increase the risk of suicidal thoughts or behavior in children and young adults.
  • May impair judgement and affect ability to drive or operate machinery.
  • May cause loss of energy, flu-like symptoms, nausea, diarrhea, increased sweating or decreased libido.
  • Interaction or overdosage may cause serotonin syndrome (symptoms include mental status changes [such as agitation, hallucinations, coma, delirium], fast heart rate, dizziness, flushing, muscle tremor or rigidity and stomach symptoms [such as nausea, vomiting, diarrhea]). Another serious syndrome, called Neuroleptic Malignant Syndrome, has also been reported; symptoms include high body temperature, muscle rigidity, and mental disturbances. Discontinue fluoxetine immediately and seek urgent medical advice if this syndrome occurs.
  • May increase risk of bleeding, especially if used with other drugs that also increase bleeding risk.
  • May also cause anxiety, nervousness or insomnia.
  • Significant weight loss has also been reported.
  • May precipitate a manic episode in people with undiagnosed bipolar disorder.
  • May cause a lowering of total body sodium (hyponatremia); elderly people or people taking diuretics or already dehydrated are more at risk.
  • May cause a discontinuation syndrome if abruptly stopped; symptoms include irritability, low mood, dizziness, electric shock sensations, headache and confusion.
  • Rarely causes seizures.
  • Seek medical advice if rash develops while taking fluoxetine: discontinue if a severe allergic reaction to fluoxetine occurs and seek urgent medical advice.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

Bottom Line

Fluoxetine is an antidepressant that is unlikely to cause drowsiness but may cause insomnia.


  • May be taken with or without food. Morning dosages may decrease risk of insomnia.
  • Be alert for changes in behavior including agitation, depressed mood, and suicide-related events and seek medical advice if changes are apparent.
  • Do not drive or operate machinery until full effects of fluoxetine are known as may impair judgement and affect ability to drive or operate machinery.
  • Seek urgent medical advice if symptoms consistent with serotonin syndrome (such as agitation, hallucinations, fast heart rate, dizziness, flushing, nausea, diarrhea) or Neuroleptic Malignant syndrome (including high body temperature, muscle rigidity, or mental disturbances) develop.

Response and Effectiveness

    Peak plasma concentrations occur within six to eight hours of a single dose. A reduction in depressive or other symptoms may be noticed within two to four weeks; however, it may take up to six to eight weeks for full effects are seen.
  • Persists for a long time in the body, so it may take a while to see an improvement in mood or a reduction in side effects with dose changes.


Fluoxetine [package insert]. Revised 12/2015. Teva Pharmaceuticals USA Inc. Accessed 02/2016

  • Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use fluoxetine only for the indication prescribed.

  • Disclaimer: Every effort has been made to ensure that this information is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. This drug information does not endorse drugs, diagnose patients or recommend therapy. It is an informational resource designed as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of this information. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.

Copyright 1996-2017 Revision Date: 2016-02-18 00:00:00