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Prozac: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Feb 28, 2023.

1. How it works

  • Prozac is a brand (trade) name for fluoxetine which may be used to treat some mood or eating disorders
  • Experts believe fluoxetine's effects are due to its ability to block the reuptake of serotonin by nerves, leading to an increase in serotonin concentrations in the nerve synapse (space between two nerves).
  • The activity of Prozac against other neurotransmitters appears much less than some other antidepressants.
  • Prozac belongs to a group of medicines called Selective Serotonin Re-uptake Inhibitors (SSRIs).

2. Upsides

  • May be used in the treatment of depression and to help maintain relief from depression in adults and children aged 8 to 18 years.
  • May be helpful for the relief of symptoms of obsessive-compulsive disorder (OCD) in adults and children aged 7 to 17 years.
  • May be useful in the treatment of the eating disorder, bulimia nervosa, to relieve moderate-to-severe symptoms such as binge eating and vomiting.
  • Has been used to treat panic disorder in adults, with or without agoraphobia (an extreme avoidance of situations that could cause panic).
  • May be used off-label to treat other conditions (this means it is not FDA-approved for this use; however, it is still a recognized use for the medicine)
  • Less likely to cause weight gain than some other antidepressants; may cause weight loss.
  • Less likely to cause sedation than some other antidepressants; may cause insomnia (sleeplessness).
  • Prozac may be used in combination with olanzapine for the treatment of depressive episodes associated with bipolar I disorder and for people with treatment-resistant depression who have not responded to two trials of antidepressants.
  • Available as a weekly dosing form that may be suitable for some people after an initial trial of Prozac daily capsules.
  • Prozac is available as a generic under the name fluoxetine.

3. Downsides

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:

  • A headache, a loss of energy, flu-like symptoms, nausea, diarrhea, weight loss, abnormal bleeding, increased sweating, or decreased libido. Anxiety, low sodium levels, and allergic reactions (including rash) can also occur. May also affect heart rhythm and trigger angle-closure glaucoma.
  • As with other antidepressants, Prozac may increase the risk of suicidal thoughts or behavior, especially in children and young adults.
  • May impair judgment and affect a person's ability to drive or operate machinery.
  • 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 Prozac immediately and seek urgent medical advice if this syndrome occurs.
  • May increase the risk of bleeding, especially if used with other drugs that also increase bleeding risk.
  • 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, or confusion. The dosage of fluoxetine should be tapered down slowly on withdrawal.
  • Rarely causes seizures.
  • May precipitate mania in people with undiagnosed bipolar disorder.
  • May interact with several other drugs including other antidepressants, tramadol, bupropion, diuretics, St John's Wort, and drugs that prolong the QT interval (such as pimozide or thioridazine).
  • May not be suitable for some people including those with glaucoma, bleeding disorders, a history of seizures, liver or kidney disease, the elderly, or certain heart conditions. People with diabetes may need the dosage of their medication adjusted.

Note: 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. View complete list of side effects

4. Bottom Line

  • Prozac may be used for the treatment of depression and other mood disorders. It is more likely to cause insomnia than drowsiness.

5. Tips

  • May be taken with or without food. Morning dosages may decrease the risk of insomnia.
  • Take Prozac exactly as directed by your doctor. Do not stop suddenly without your doctor's advice. Prozac is best tapered down slowly on discontinuation.
  • Be alert for worsening mood and suicide-related thoughts or behaviors. Seek medical advice if changes are apparent.
  • Do not drive or operate machinery if Prozac impairs your judgment or makes you sleepy.
  • 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.
  • Talk to your doctor immediately if you develop a rash or seek urgent medical advice with severe allergy-type symptoms such as swelling of the face or throat, or shortness of breath.
  • Do not take any other medicines, including those bought over-the-counter, without first consulting a doctor or pharmacist and asking if the medicine is safe to take with Prozac.
  • If you have diabetes, you may need to monitor your blood sugar levels more regularly on the initiation of Prozac and with any dosage change. Talk to your doctor if your blood sugar levels are not as well controlled as they use to be.
  • Talk with your doctor if you experience any unusual bruising or increased bleeding while taking Prozac; persistent headaches, confusion, weakness, or unsteadiness resulting in falls; an increase, irregularity, or slowing of your heart rate or shortness of breath; or a rash. Also report any eye pain, eye swelling, or visual disturbances; seizures; manic behavior such as recklessness, racing thoughts, increased energy, or severe difficulty sleeping.

6. 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 before 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.

7. Interactions

Medicines that interact with Prozac may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with Prozac. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with Prozac include:

  • anticoagulants (blood thinners), such as warfarin, or other drugs that have blood-thinning effects such as aspirin or NSAIDs
  • anticonvulsants, such as phenytoin, phenobarbital, or primidone
  • antipsychotics (such as butyrophenones, phenothiazines, or thioxanthenes) and atypical antipsychotics (eg, olanzapine, quetiapine, ziprasidone)
  • any medication that may cause drowsiness, such as benzodiazepines (eg, diazepam, lorazepam), first-generation antihistamines (such as doxylamine or promethazine), metoclopramide, or opioids (such as codeine, morphine)
  • diuretics, such as furosemide
  • lithium
  • medications that may affect the heartbeat by prolonging the QT interval, such as amiodarone, encainide, or flecainide
  • pimozide
  • other antidepressants, such as tricyclic antidepressants (eg, amitriptyline), monoamine oxidase inhibitors (eg, isocarboxazid, phenelzine, and tranylcypromine), and SSRIs (eg, paroxetine, sertraline)
  • other medications that affect serotonin, such as amphetamines, fentanyl, lithium, tramadol, triptans (eg, almotriptan, eletriptan, or sumatriptan), or St. John's Wort
  • other medications that are metabolized by the same enzymes (CYP2D6) such as tricyclic antidepressants, most antipsychotics, flecainide, propafenone, or vinblastine
  • thioridazine (do not administer at the same time as Prozac or for 5 weeks after Prozac has been discontinued)
  • others, such as HIV medications (fosamprenavir, ritonavir), procyclidine, or theophylline.

Avoid drinking alcohol or taking illegal or recreational drugs while taking Prozac.

Note that this list is not all-inclusive and includes only common medications that may interact with Prozac. You should refer to the prescribing information for Prozac for a complete list of interactions.


Further information

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

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2023 Revision date: February 28, 2023.