Fluoxetine is a type of antidepressant known as an SSRI (selective serotonin reuptake inhibitor).
Fluoxetine helps many people recover from depression, and it has fewer unwanted effects than older antidepressants.
Fluoxetine is available only on prescription. It comes as tablets and capsules.
- It usually takes 4 to 6 weeks for fluoxetine to work.
- Common side effects include feeling sick, headaches and trouble sleeping. They are usually mild and go away after a couple of weeks.
- Fluoxetine can affect an unborn baby. Tell your doctor straight away if you're trying to get pregnant or become pregnant while taking it.
- Fluoxetine can cause withdrawal symptoms. Don't stop taking it without talking to your doctor.
- Fluoxetine is called by the brand name Prozac.
Who can and can't take fluoxetine
Fluoxetine can be taken by adults for depression, obsessive compulsive disorder and bulimia.
Fluoxetine can be taken by children aged 8 or older for depression.
Check with your doctor before starting to take fluoxetine if you:
- have had an allergic reaction to fluoxetine or any other medicines in the past
- have a heart problem, as fluoxetine can speed up or change your heartbeat
- have ever taken any other medicines for depression. Some rarely used antidepressants can interact with fluoxetine to cause very high blood pressure even when they have been stopped for a few weeks
- are trying to become pregnant, are already pregnant or you are breastfeeding - fluoxetine is not usually recommended in pregnancy or while breastfeeding
- have an eye problem called glaucoma because fluoxetine can increase the pressure in your eye
If you have diabetes, fluoxetine can make it more difficult to keep your blood sugar stable. Monitor your blood sugar more often for the first few weeks of treatment with fluoxetine and adjust your diabetes treatment if necessary.
How and when to take
Take fluoxetine once a day. It doesn't upset the stomach so you can take it with or without food.
You can take fluoxetine at any time, as long as you stick to the same time every day. If you have trouble sleeping, it's best to take it in the morning.
How much will I take?
The usual dose of fluoxetine is 20mg a day in adults. However, you may be started at a lower dose which is gradually increased to a maximum dose of 60mg a day. Some people might need to take a lower dose of fluoxetine, or to take it less often. This includes people with liver problems, and elderly people.
The usual dose of fluoxetine in children is 10mg a day but this may be increased to 20mg a day.
What if I forget to take it?
If you occasionally forget to take a dose, don’t worry. Take your next dose the next day at the usual time. Never take 2 doses at the same time to make up for a forgotten one.
If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.
What if I take too much?
Ask your doctor for advice straight away as an overdose can lead to potentially serious symptoms such as:
- feeling sleepy
- heart problems
- lung problems
Like all medicines, fluoxetine can cause side effects in some people, but many people have no side effects or only minor ones. Some of the common side effects of fluoxetine will gradually improve as your body gets used to it.
Common side effects
These side effects happen in more than 1 in 100 people. Keep taking the medicine, but tell your doctor or pharmacist if these side effects bother you or don't go away:
- feeling sick
- being unable to sleep
- feeling tired or weak
Serious side effects
It happens rarely (in less than 1 in 100 people), but some people may have serious side effects when taking fluoxetine.
Tell a doctor straight away if you get:
- low sodium levels – warning signs include headache, trouble focusing, memory problems, not thinking clearly, weakness, seizures, or losing your balance
- thoughts about harming yourself or ending your life
- chest pain or pressure, or shortness of breath
- severe dizziness or passing out
- fits, feelings of euphoria, excessive enthusiasm or excitement, or a feeling of restlessness that means you can't sit or stand still
- putting on or losing weight without trying to
- changes in your periods such as heavy bleeding, spotting, or bleeding between periods
- painful erections that last longer than 4 hours – this may happen even when you are not having sex
Or, if you get any signs of abnormal bleeding including:
- bleeding from the gut – warning signs include vomiting blood or dark vomit, coughing up blood, blood in your pee, black or red poo
- bleeding from the gums or bruises that appear without a reason or that get bigger
- any bleeding that is very bad or that you cannot stop
Serious allergic reaction
In rare cases, it’s possible to have a serious allergic reaction to fluoxetine.
A serious allergic reaction is an emergency. Contact a doctor straight away if you think you or someone around you is having a serious allergic reaction.
The warning signs of a serious allergic reaction are:
- getting a skin rash that may include itchy, red, swollen, blistered or peeling skin
- tightness in the chest or throat
- having trouble breathing or talking
- unusual hoarseness
- swelling of the mouth, face, lips, tongue, or throat
These are not all the side effects of fluoxetine. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect to the UK safety scheme.
How to cope with side effects
You can reduce the chance of having a side effect if you take fluoxetine in the evening so that you're asleep when the level of medicine in your body is highest.
What to do about:
- feeling sick – try taking fluoxetine with or after food. It may also help to stick to simple meals and avoid rich or spicy food.
- being unable to sleep – take fluoxetine first thing in the morning
- diarrhoea – drink plenty of water or other fluids. It may also help to take oral rehydration solutions you can buy from a pharmacy to prevent dehydration. Don't take any other medicines to treat diarrhoea or vomiting without speaking to a pharmacist or doctor
Pregnancy and breastfeeding
Fluoxetine is generally not recommended in pregnancy or while breastfeeding.
No antidepressants are considered completely safe to take in pregnancy or while breastfeeding. Your doctor will only want to prescribe fluoxetine when the benefits of taking the medicine outweigh the risks.
Fluoxetine and similar antidepressants have been linked with a small risk of problems for the unborn baby when they're taken in early or late pregnancy.
Fluoxetine and breastfeeding
Fluoxetine is not usually recommended if your're breastfeeding. Fluoxetine passes into breast milk and has been linked with side effects in breastfed babies.
Cautions with other medicines
Some medicines and fluoxetine can interfere with each other and increase the chances of you having side effects.
Tell your doctor if you're taking these medicines before you start fluoxetine:
- any medicines that affect your heartbeat – as fluoxetine can speed up or change your heartbeat
- any other medicines for depression. Some rarely used antidepressants can interfere with fluoxetine to cause very high blood pressure even when they have been stopped for a few weeks
Mixing fluoxetine with herbal remedies and supplements
Do not take the herbal remedy, St John's wort, for depression while you are being treated with fluoxetine as this will increase your risk of side effects.
How does fluoxetine work?
When will I feel better?
How will it make me feel?
How long will I take it for?
Is it safe to take it for a long time?
What will happen if I come off fluoxetine?
Is fluoxetine better than other antidepressants?
Will it affect my contraception?
Will it affect my sex life?
Will I gain or lose weight?
Can I drive or ride a bike?
Can I drink alcohol with it?
Will recreational drugs affect it?
Is there any food or drink I need to avoid?
Are there other treatments that will help?