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Fluoxetine: uses, benefits and side effects

Blackboard with the chemical compounds of Fluxetine
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Quick facts

  • Fluoxetine was first discovered by the global pharmaceutical company Lilly in 1972. It became available for medical use in 1986.
  • 6.5 million items of fluoxetine were prescribed in the UK in 2017 - weighing nearly 6,000 kg in total (source: openprescribing.net).
  • Fluoxetine is the generic name for the brand-name medicines Prozac, Olena and Prozep.

What is fluoxetine?

Fluoxetine (floo-OX-eh-teen) is a commonly prescribed antidepressant of the selective serotonin reuptake inhibitor (SSRI) class.

It is often prescribed to treat depression, as well as panic attacks, obsessive-compulsive disorder (OCD) and bulimia nervosa.

Fluoxetine is only available on prescription, and comes as tablets, dispersible tablets, capsules, oral solution and oral suspension.

How does fluoxetine work?

Like other SSRIs, fluoxetine works by helping to restore the balance of serotonin in the brain. It’s thought that low levels of serotonin may contribute to depression, and fluoxetine responds to this by boosting the amount of circulating serotonin available in your system.

The effects of fluoxetine should be seen around four to six weeks after beginning treatment.

Fluoxetine dosage

Fluoxetine is available as 10mg film-coated tablets, 20mg and 60mg capsules, and also as a 20mg/5ml oral solution.

The usual dose for adults is 20mg a day, although you may be started at a lower dose which is gradually increased to a maximum daily dose of 60mg.

The amount of fluoxetine you need to take depends on the dose that your GP feels will best alleviate your symptoms or particular condition. 

How to take fluoxetine

Fluoxetine can be taken as a single dose or in divided doses, during or between meals.

It’s up to you when to take fluoxetine; just make sure you stick to the same time every day. If you’re having trouble sleeping, it’s best to take it in the morning.

Do not crush, break or chew the tablets - take them whole with a glass of water.

If you forget to take a dose, take it as soon as possible unless it’s almost time for your next dose. Do not take two doses together. Using LloydsDirect can help you keep on top of your doses.

For more advice on taking fluoxetine, be sure to check the Patient Information Leaflet (PIL) included in your medication packaging.

What are the side effects of fluoxetine?

Common side effects of fluoxetine (which happen in more than 1 in 100 people) include:

  • Vomiting, dry mouth, weight decrease
  • Dizziness, tremors, disturbance in attention
  • Agitation, anxiety, nervousness, sleep disorder

Serious side effects are rare (less than 1 in 100 people).

Tell your straight away GP if any of these side effects occur:

  • Brain fog (trouble focusing, memory problems, not thinking clearly and losing your balance can all be signs of low sodium levels)
  • Thoughts of self-harm or suicide
  • Severe dizziness
  • Chest pain
  • Shortness of breath
  • Changes in your menstrual cycle
  • Painful erections that last hours even when you’re not having sex
  • Any symptoms of abnormal bleeding (coughing blood, blood in your pee, bleeding gums or bruises on your body with no apparent reason)

If you feel as though your course of fluoxetine is causing unwanted side effects, your GP may decide to adjust your dose depending on the severity of the side effects.

1 in 100 people who take fluoxetine will experience side effects, including headaches and dizziness.

Fluoxetine interactions

When you stop taking fluoxetine, the active drug substances will persist in your body for up to six weeks. This means a new medication can still interact with the fluoxetine that remains in your system.

If you have been prescribed fluoxetine, you should not take:

  • Medicines for heart rhythm problems (e.g. Class IA and III antiarrhythmics)
  • MAOI-A antidepressants (including linezolid and methylthioninium chloride)
  • Mequitazine
  • Tamoxifen
  • Phenytoin
  • St John’s Wort

A full list of interactions with fluoxetine can be found here.

If you have recently taken or are taking any other medication before starting your fluoxetine course, let your GP or pharmacist know as soon as possible.

Fluoxetine contraindications

There are some instances where it may not be safe to take fluoxetine.

Speak to your GP if you are:

  • Hypersensitive to fluoxetine
  • Taking irreversible, non-selective MAOIs (such as iproniazid)
  • Taking metoprolol, which is used in instances of cardiac failure

Taking fluoxetine during pregnancy or while breastfeeding

You should not take fluoxetine if you are pregnant. Some studies suggest an increased risk for the baby to be born with cardiovascular problems.

It’s also not recommended to take fluoxetine if you are breastfeeding, because it passes into breast milk and has been linked with side effects in breastfed babies.

Fluoxetine and alcohol

If you are on a course of fluoxetine, drinking alcohol is not advisable. You may find that booze can cause unwanted side effects such as drowsiness and loss of coordination, so certainly err on the side of caution when you attend work drinks.

Speak with your GP or pharmacist if you intend to drink while taking fluoxetine.

What’s the easiest way to get fluoxetine?

Been authorised by your GP to take fluoxetine on repeat prescription? Cut out the stress and order with LloydsDirect today.