Fluoxetine. Drug and Patient Information. Dosage. Overdose. Generic or Brand Fluoxetine. For Professionals and Consumers.

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Fluoxetine is prescribed for the treatment of depression, that is, a continuing depression that interferes with daily functioning. The symptoms of major depression often include changes in appetite, sleep habits, and mind/body coordination; decreased sex drive; increased fatigue; feelings of guilt or worthlessness; difficulty concentrating; slowed thinking; and suicidal thoughts.

Fluoxetine is also prescribed to treat obsessive-compulsive disorder. An obsession is a thought that won’t go away; a compulsion is an action done over and over to relieve anxiety. Fluoxetine is also used in the treatment of bulimia (binge-eating followed by deliberate vomiting). It has also been used to treat other eating disorders and obesity.

In addition, Fluoxetine is used to treat panic disorder, including panic associated with agoraphobia (a severe fear of being in crowds or public places). People with panic disorder usually suffer from panic attacks–feelings of intense fear that develop suddenly, often for no reason. Various symptoms occur during the attacks, including a rapid or pounding heartbeat, chest pain, sweating, trembling, and shortness of breath.

Fluoxetine is a member of the family of drugs called “selective serotonin re-uptake inhibitors.” Serotonin is one of the chemical messengers believed to govern moods. Ordinarily, it is quickly reabsorbed after its release at the junctures between nerves. Re-uptake inhibitors such as Fluoxetine slow this process, thereby boosting the levels of serotonin available in the brain.

Brand name: Prozac

Generic Name: Fluoxetine


Most important fact about Fluoxetine

Serious, sometimes fatal, reactions have been known to occur when Fluoxetine is used in combination with other antidepressant drugs known as MAO inhibitors, including Nardil and Parnate; and when Fluoxetine is discontinued and an MAO inhibitor is started. Never take Fluoxetine with one of these drugs or within at least 14 days of discontinuing therapy with one of them; and allow 5 weeks or more between stopping Fluoxetine and starting an MAO
inhibitor. Be especially cautious if you have been taking Fluoxetine in high doses or for a long time.

If you are taking any prescription or nonprescription drugs, notify your doctor before taking Fluoxetine.

How should you take Fluoxetine?

Fluoxetine should be taken exactly as prescribed by your doctor.

Fluoxetine usually is taken once or twice a day. To be effective, it should be taken regularly. Make a habit of taking it at the same time you do some other daily activity.

It may be 4 weeks before you feel any relief from your depression, but the drug’s effects should last about 9 months after a 3-month treatment regimen. For obsessive-compulsive disorder, the full effect may take 5 weeks to appear.

If you miss a dose of Fluoxetine

Take the forgotten dose as soon as you remember. If several hours have passed, skip the dose. Never try to “catch up” by doubling the dose.

Storage instructions for Fluoxetine

Store at room temperature.

What side effects may occur when taking Fluoxetine?

Side effects cannot be anticipated.

If any develop or change in intensity, inform your doctor as soon as possible. Only your doctor can determine if it is safe for you to continue taking Fluoxetine.

More common side effects of Fluoxetine may include:

Abnormal dreams, abnormal ejaculation, abnormal vision, anxiety, diminished sex drive, dizziness, dry mouth, flu-like symptoms, flushing, gas, headache, impotence, insomnia, itching, loss of appetite, nausea, nervousness, rash, sinusitis, sleepiness, sore throat, sweating, tremors, upset stomach, vomiting, weakness, yawning

Less common side effects of Fluoxetine may include:

Abnormal taste, agitation, bleeding problems, chills, confusion, ear pain, emotional instability, fever, frequent urination, high blood pressure, increased appetite, loss of memory, palpitations, ringing in the ears, sleep disorders, weight gain

In children and adolescents, less common side effects may also include:

Agitation, excessive menstrual bleeding, frequent urination, hyperactivity, mania or hypomania (inappropriate feelings of elation and/or rapid thoughts), nosebleeds, personality changes, and thirst

A wide variety of other very rare reactions have been reported during Fluoxetine therapy. If you develop any new or unexplained symptoms, tell your doctor without delay.

Why should Fluoxetine not be prescribed?

If you are sensitive to or have ever had an allergic reaction to Fluoxetine or similar drugs such as Paxil and Zoloft, you should not take this medication. Make sure that your doctor is aware of any drug reactions that you have experienced.

Do not take Fluoxetine while using an MAO inhibitor.

You should also not use Fluoxetine if you are taking Mellaril (thioridazine).

Likewise, do not start taking Mellaril within 5 weeks of stopping Fluoxetine.

Special warnings about Fluoxetine

Unless you are directed to do so by your doctor, do not take this medication if you are recovering from a heart attack or if you have liver disease or diabetes.

Fluoxetine may cause you to become drowsy or less alert and may affect your judgment. Therefore, driving or operating dangerous machinery or participating in any hazardous activity that requires full mental alertness is not recommended.

While taking Fluoxetine, you may feel dizzy or light-headed or actually faint when getting up from a lying or sitting position. If getting up slowly doesn’t help or if this problem continues, notify your doctor.

If you develop a skin rash or hives while taking Fluoxetine, discontinue use of the medication and notify your doctor immediately.

Fluoxetine should be used with caution if you have a history of seizures. You should discuss all of your medical conditions with your doctor before taking this medication.

Fluoxetine can occasionally cause decreased appetite and weight loss, especially in depressed people who are already underweight and in those with bulimia. If you notice changes in your weight or appetite, tell your doctor.

Possible food and drug interactions when taking Fluoxetine

Combining Fluoxetine with MAO inhibitors or Mellaril (thioridazine) is dangerous.

Do not drink alcohol while taking this medication.

If Fluoxetine is taken with certain other drugs, the effects of either could be increased, decreased, or altered.

It is especially important to check with your doctor before combining Fluoxetine with the following:
this calming agent (this anxiety treatment)
Carbamazepine (Tegretol)
Clozapine (Clozaril)
this tranquilizer (this sedative)
Digitoxin (Crystodigin)
Drugs that impair brain function, such as sleep aids and narcotic
Flecainide (Tambocor)
Haloperidol (Haldol)
Lithium (Eskalith)
Other antidepressants (Elavil)
Phenytoin (Dilantin)
Pimozide (Orap)
Vinblastine (Velban)
Warfarin (Coumadin)

Special information if you are pregnant or breastfeeding

The effects of Fluoxetine during pregnancy have not been adequately studied. If you are pregnant or plan to become pregnant, inform your doctor immediately. This medication appears in breast milk, and breastfeeding is not recommended while you are taking Fluoxetine.

Recommended Fluoxetine dosages


The usual starting dose is 20 milligrams per day, taken in the morning. Your doctor may increase your dose after several weeks if no improvement is observed. People with kidney or liver disease, the elderly, and those taking other drugs may have their dosages adjusted by their doctor.

Dosages above 20 milligrams daily should be taken once a day in the morning or in 2 smaller doses taken in the morning and at noon.

The usual daily dose for depression ranges from 20 to 60 milligrams. For obsessive-compulsive disorder the customary range is 20 to 60 milligrams per day, though a maximum of 80 milligrams is sometimes prescribed. For bulimia nervosa, the usual dose is 60 milligrams, taken in the morning. Your doctor may have you start with less and build up to this dosage. The usual dose for premenstrual dysphoric disorder is 20 milligrams a day.

For depression, it may take up to 4 weeks before the full effects of the medication are seen. For obsessive-compulsive disorder, treatment can take 5 weeks or more to be effective.

If you are taking a 20-milligram daily dose of Fluoxetine for depression, the doctor may switch you to a delayed-release formulation called Fluoxetine Weekly. To make the change, you’ll be asked to skip your daily dose for 7 days, then take your first weekly capsule.


The usual starting dose for depression is 10 or 20 milligrams a day. After 1 week at 10 milligrams a day, the doctor may increase the dose to 20 milligrams. It may take up to 4 weeks before the full effects of the medication are seen.

For obsessive-compulsive disorder, the usual starting dose is 10 milligrams a day. After 2 weeks, the doctor may increase the dose to 20 milligrams. If no improvement is seen after several weeks, the dosage may be increased as needed, up to a maximum of 60 milligrams a day. Treatment may take 5 weeks or more to be effective.

Children who are underweight, have kidney or liver problems, or are taking multiple medications may need their dosages adjusted by their doctor.

Overdosage of Fluoxetine

Any medication taken in excess can have serious consequences. An overdose of Fluoxetine can be fatal. In addition, combining Fluoxetine with certain other drugs can cause symptoms of overdose. If you suspect an overdose, seek medical attention immediately.

Common symptoms of Fluoxetine overdose include:

Nausea, rapid heartbeat, seizures, sleepiness, vomiting.

Other symptoms of Fluoxetine overdose include:

Coma, delirium, fainting, high fever, irregular heartbeat, low blood pressure, mania, rigid muscles, sweating, stupor.