HeadMeds gives young people in the United Kingdom general information about medication. HeadMeds does not give you medical advice. Please talk to your Doctor or anyone else who is supporting you about your own situation because everyone is different. Please read more important details about our site.

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Fluoxetine

Return to Fluoxetine overview
  1. Use and Action
  2. Warnings and side effects
  3. Sex, drink, weight and everything else
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Taking Fluoxetine, Haloperidol, Diazepam, Olanzapine
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Fluoxetine can be used to treat the following conditions

Headmeds fills the medicines information gaps for young people - things you might want to know about meds like will it affect my sex life? Can I still study? Can I drink?
Headmeds does not give medical advice so this is just general information.
Each medicine has a balance of good and bad effects, and each person gets their own individual effects.
You might want to know just one thing about your medicine, but on each page we have given you the ‘safety headlines’. Please read them as they are important.
We have included lots of information about each medicine - but if you want all the details, please look at the patient information leaflet - which is inside every pack. These leaflets are also at www.medicines.org.uk - where there will be the most up-to-date information.

Safety headlines

  • If you have taken more fluoxetine than it said on the label, you must see a doctor quickly – even if you do not feel any different.
  • Fluoxetine can make some people think about hurting themselves or committing suicide. You must go straight to hospital with your tablets if you have any of these thoughts.
  • Fluoxetine can also cause rare but serious side effects: allergic reactions (difficulty breathing, swelling of your face or throat, itching skin lumps), rashes or blotches on your skin, and a rare condition called serotonin syndrome (see ‘Warnings and Side Effects’). Go to a hospital if you get any of these symptoms with your medicine.
  • Do not take fluoxetine if you have taken a monoamine oxidase inhibitor antidepressant (MAOI) like moclobemide, phenelzine, isocarboxazid or tranylcypromine in the last 14 days.
  • Stopping fluoxetine suddenly can sometimes cause side effects, which are usually mild, but for a few people can be severe. Also, if you stop taking fluoxetine too soon, there is more chance that your mental health symptoms will come back. See your doctor if you want to stop fluoxetine or have side effects after stopping it.
  • You might not be able to concentrate very well, and may feel sleepy, in the first few days after taking fluoxetine – do not drive a car, ride a bike or operate machines until you see how this affects you.
  • If you are pregnant, or thinking of becoming pregnant, please read the pregnancy section (see ‘Sex, drink, weight and everything else’) because fluoxetine may affect the developing baby.

Basic details

Fluoxetine is a type of antidepressant called a Selective Serotonin Re-uptake Inhibitor

A Selective Serotonin Re-uptake Inhibitor (SSRI) helps make more serotonin available in your brain.

Fluoxetine can be used to help with low mood and anxiety

  • It will sometimes be prescribed alongside a ‘talking’ therapy”.

The capsules contain gelatin,  the liquid contains a small amount of sugar and alcohol

  • The capsules contain gelatine, which some people do not like to eat because of religious or cultural beliefs.
  • The liquid contains a small amount of sugar (sucrose).
  • The liquid also contains a small amount of alcohol, but it would not affect your blood alcohol levels.

Fluoxetine can be used for a number of conditions

  • Low mood (depression)
  • Anxiety
  • Eating disorders such as bulimia nervosa and binge eating disorder
  • Bipolar depression
  • Panic Disorder
  • Generalised Anxiety Disorder
  • Obsessive Compulsive Disorder
  • Body Dysmorphic Disorder
  • Social anxiety
  • Phobias

Fluoxetine can help to adjust the chemicals your brain needs 

  • Serotonin is a naturally occurring chemical messenger (or “neurotransmitter”) that has important roles in areas of the brain that control mood and thinking.
  • There is evidence that in people with depression, there are changes in the brain that compromise the function of serotonin as a messenger.
  • Medicines like fluoxetine are called selective serotonin reuptake inhibitors (SSRIs) because they stop serotonin being taken back up into nerve cells. This increases the levels of serotonin between the cells to send messag.
  • At first, the nerve cells sense this increase in serotonin levels and start to release less serotonin in order to keep the levels the same.
  • However, due to the way the nerve cells regulate their own activity, the amount of serotonin released by the nerve cells increases slowly over time. The eventual increase in serotonin levels helps to lift the depression and anxiety.
  • This is the leading theory as to why it takes time for the beneficial effects of SSRIs like fluoxetine to develop. However, there are other theories, and we do not yet have a full understanding of what happens in depression or how antidepressants work

Fluoxetine is taken once a day

  • You will get the best effect from fluoxetine if you take it regularly every day.
  • Make sure that you know your dose. If it is not written on the label, check it with your pharmacist or doctor.
  • Young people aged 8-18 may start taking fluoxetine at a lower dose using the liquid, and then move on to the capsules if the dose increases.
  • It is usually best to take fluoxetine in the morning. This is to reduce the chance of it causing difficulty sleeping (insomnia). However, it is important to choose a time each day that you can always remember. This could be when you wake up, a mealtime, or when you brush your teeth.
  • You can take it before or after food.
  • Swallow the capsule with a drink of water - if you chew it, it tastes bitter.

If you forget to take a dose then just take it as soon as possible, but do not double dose

What to do if you miss a dose:

  • If you remember later during the day, take it as soon as possible.
  • You may find it difficult to sleep if you take it towards bedtime.
  • If you forget to take it by the time of your next dose, just take the next dose.
  • Do not take a double dose.

What might happen?

  • If you forget to take it for a few days, you may start getting withdrawal symptoms and should talk to your doctor about it.

You must go to A&E if you take too much 

What to do if you take too much:

  • If you have taken more fluoxetine than it said on the label, you must get help quickly – even if you do not feel any different.
  • Go to A&E. Take your medicine with you, to show to the doctors. Tell them how much you have taken.
  • Get a friend or family member to go with you, if you can, just in case you feel ill on the way.
  • You might get any of the following signs:
  • feeling sick or being sick
  • having fits
  • an irregular heartbeat or a heart attack
  • lung problems
  • a change in the way you feel, ranging from agitation to falling into a coma.

You are also at risk of getting ‘Serotonin syndrome’. This is when you can get a high fever, agitation, confusion, trembling, shivering and excessive sweating or weird movements of your muscles. This is rare, but you should watch out for it.

It can take 2-3 weeks for fluoxetine to start helping  

  • Antidepressants like fluoxetine can start to work on depression within the first two weeks of treatment, and the improvement continues over the following few weeks.
  • For anxiety, antidepressants like fluoxetine can take slightly longer to work. For some people, anxiety briefly increases at the start of treatment, but the anxiety does decrease with continued treatment.
  • See ‘Fluoxetine can help to adjust the chemicals your brain needs’ for the theory as to why it takes time for the benefit of fluoxetine to develop.
  • Some side effects of fluoxetine tend to happen at the start of treatment, but go away after a few days, such as feeling or being sick (nausea or vomiting).
  • To get the best effect, you need to take your fluoxetine every day and give it a chance to work for you.
  • Your doctor might start you on a low dose and then increase it slowly over two to four weeks to your full dose.

Most people take fluoxetine for at least 6 months 

  • You and your doctor should talk about how long you need to take fluoxetine.
  • It could take a long time to work for you, but hopefully it will be worth sticking with it.
  • Keep taking fluoxetine as you get better, which can take a few months, and then keep taking the fluoxetine for another 6 to 12 months as advised by your doctor. If your illness has come back, then you should keep taking fluoxetine for at least two years after getting better.
  • This will help keep you well. If you stop taking the fluoxetine too soon, there is more chance that your mental health symptoms will come back.
  • If you get side-effects that you cannot live with, then talk to your doctor about other options.
  • See your doctor if you want to stop fluoxetine to make sure it is not too soon to stop it. Also, the fluoxetine dose may need to be reduced gradually to reduce the chance of side effects when it is stopped.
  • If you have bipolar disorder, it is likely that the doctor will advise for the fluoxetine to be stopped sooner. This is because, in bipolar disorder, there is a risk of your mood becoming too high if an antidepressant is used for too long.

Reference sources

  • Prozac capsules and liquid SPC last updated 13/3/13
    http://www.medicines.org.uk/emc/medicine/504/SPC/Prozac+20mg+hard+capsules%2c+and+20mg+per+5ml+oral+liquid/
    Accessed 6/3/14
  • Prozac capsule PIL last updated 11/3/13
    http://www.medicines.org.uk/emc/medicine/2513/XPIL/Prozac+20mg+hard+capsules/ Accessed 6/3/14
  • Taylor D, Paton C, Kapur S. Maudsley Prescribing Guidelines in Psychiatry, 11th edition. Oxford: John Wiley & Sons, 2012
  • British National Formulary (BNF) 66th edition. London: BMJ Group / Pharmaceutical Press, 2013
  • British National Formulary for Children (BNFc) 2013-2014. London: BMJ Group / Pharmaceutical Press, 2013
  • WADA Prohibited List 2014. Available at http://www.wada-ama.org/Documents/World_Anti-Doping_Program/WADP-Prohibited-list/2014/WADA-prohibited-list-2014-EN.pdf
  • Neal MC. Medical Pharmacology at a Glance (7th Edition). Oxford: John Wiley & Sons, 2012
  • Royal Pharmaceutical Society of Great Britain. Medicines Ethics and Practice (37th edition). London: RPS, 2013
  • www.choiceandmedication.org (accessed 23/10/2016; content usually available for free via your mental health trust)
  • National Institute for Health and Care Excellence. Depression in adults: The treatment and management of depression in adults. Clinical Guideline Number 90. London: National Institute for Health and Care Excellence; 2009.
  • Cowen P, Harrison P, Burns T. Shorter Oxford Textbook of Psychiatry, 6th edition. Oxford: Oxford University Press, 2012.
  • www.choiceandmedication.org (content usually available for free via your mental health trust).
  • National Institute for Health and Care Excellence. Depression in adults: The treatment and management of depression in adults. Clinical Guideline Number 90. London: National Institute for Health and Care Excellence; 2009.
  • Cowen P, Harrison P, Burns T. Shorter Oxford Textbook of Psychiatry, 6th edition. Oxford: Oxford University Press, 2012.