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What is fluoxetine?

Fluoxetine is pronounced ‘flew-ox-e-teen’.

Fluoxetine (also called Prozac®) is mainly used to help treat the symptoms of depression (by reducing the time it takes to recover), anxiety, and OCD. It can also help social anxiety, PTSD, panic, PMS and seasonal affective disorder.

It is often known as a selective serotonin reuptake inhibitor (SSRI).

It is made as capsules, a dispersible tablet and a liquid.

What does fluoxetine help?

Fluoxetine can help with:

  • feeling low
  • nervous
  • very shy
  • panicky
  • having to do things exactly the right way and checking all the time

In lower doses (such as 10mg a day), it can help anxiety, worries and distress.


For depression, about 2 in 3 people get better with a first antidepressant.

If that does not work or it has too many side effects, then switching to another antidepressant means about 1 in 2 of those people get better.

There are other options after that such as other medicines and therapies.

How and when should I take fluoxetine?

Swallow the capsules with some water whilst sitting or standing. This is to make sure that they reach the stomach and do not stick in your throat.

For the liquid, use a medicine spoon, dropper or oral syringe.

For a dispersible tablet, disperse in half a glass of water and drink.

It is best taken with or after food, in the morning.

How long will I have to wait before it works?

This will depend on what you are taking it for.

With depression, the effect usually starts in 1 or 2 weeks, and builds over the next couple of weeks.

For some other conditions it may take up to 3 months to work.

How long will I need to take fluoxetine for?

This will depend on what you are taking it for.

What if I do not want to take fluoxetine anymore?

Do not stop taking fluoxetine suddenly.

It is better not to do this without talking it over first with other people such as your family, prescriber, nurse, pharmacist or other healthcare professional.

It normally works out much better if you stop medication in a planned way at a time when your stress levels are lower, rather around exam times, mid-winter and life events.

Your symptoms can return if treatment is stopped too early. This may happen some weeks or even months after you stop taking fluoxetine.

You might also get some discontinuation symptoms such as ‘flu-like symptoms, and sleep disturbance (such as more vivid dreams). They can start 1 to 2 weeks after stopping, usually only last a few weeks (but can be a bit longer).

What should I do if I forget to take a dose?

Start again as soon as you remember if within about 12 hours of your next dose. After this just take the next dose as normal.

Do not try to catch up by taking 2 doses at once as you may get more side-effects.

Can I cycle or drive while I am taking fluoxetine?

You may feel a bit light-headed at first when taking fluoxetine.

Until this wears off, or you know how fluoxetine affects you, be careful cycling and, do not drive or operate machinery.

What are the side effects of fluoxetine?

Very common

More than 1 in 10 people might get these:

  • Feeling sick or being sick, or stomach pain. It may help to take your dose after eating some food. It will usually wear off in a few weeks. If it does not wear off, please tell your prescriber.
  • Not being able to sleep at night. To avoid this, make you take the dose early in the day. Let your prescriber know as a change in dose may help.
  • Changes with sex. Finding it hard to have an orgasm or having no desire for sex. Discuss this with your prescriber.


Fewer than 1 in 10 people may get these:

  • Headaches. If your head is painful, paracetamol usually helps.
  • Not feeling hungry. You will usually get your appetite back in a few weeks. If not, let your prescriber know next time you meet.
  • Diarrhoea or going to the toilet more than usual. Drink plenty of water and get advice from your pharmacist. If it lasts for more than a day or so, contact your prescriber.
  • Feeling more anxious or nervous. This usually only lasts for a few weeks while you get used to your SSRI. If not, tell your prescriber next time you meet.

Rare side effects

Please see your prescriber if you get any of these rare side effects:

  • Thoughts of harming yourself. Feeling anxious, restless, poor sleep and feeling you might want to harm yourself. See your doctor in the next day, especially if you are under 20 years old, started the medicine in the last few weeks, have had a dose change or may have bipolar depression.
  • Serotonin Syndrome. You may feel: confused, agitated, restless, sweaty, feverish, fast heart beat, twitching, shivering and shaky. It may happen if you have just started, had a dose increase, overdose, or start to take any other medicines. See your doctor in the next few hours if this happens.
  • Rash or itching seen anywhere on the skin. If this happens, stop taking your SSRI and contact your prescriber in the next day.
  • Hyponatremia or SIADH. You do not pass much urine, are tired, confused, muscle cramps and you can get a headache. This can be dangerous so contact your prescriber now.

Some side effects are the brain getting used to a medicine and these usually wear off in a few days or weeks. Starting slower may help. If you think you might have a side effect, you should ask your prescriber, pharmacist or other healthcare professional.

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Please note: this is a generic information sheet relating to care at Sheffield Children’s NHS FT. These details may not reflect treatment at other hospitals. This information is not intended as a substitute for professional medical care. Always follow your healthcare professionals’ instructions. If this resource relates to medicines, please read it alongside the medicine manufacturer’s patient information leaflet. If this information has been translated into another language from English, efforts have been made to maintain accuracy, but there may still be some translation errors. If you are unsure about any of the guidance in this resource or have specific questions about how it relates to your child, always ask your healthcare professional for further advice.

Resource number: MH76

Resource Type: Article

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