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Fluoxetine for the treatment of cataplexy in narcolepsy

What is cataplexy in narcolepsy?

Narcolepsy is a long-term condition which causes excessive sleepiness during the day and may disrupt your sleep at night. You can also have sleep attacks where you fall asleep at inappropriate times during the day without any warning.

Cataplexy is a condition associated with narcolepsy that results in sudden muscle weakness. This can be triggered by strong emotions such as:

  • laughter
  • anger
  • fright
  • surprise

Muscle weakness can vary in severity, and cataplexy attacks can differ in both type and how long they last for.

What is fluoxetine?

Fluoxetine belongs to a group of medicines called anti-depressants. It can be used to treat cataplexy in narcolepsy. Fluoxetine works by interfering with certain chemicals in the brain which may be involved in causing the symptoms of cataplexy.

Taking an unlicensed medicine

Fluoxetine for the treatment of narcolepsy is unlicensed. This means that the manufacturer of the medicine has not specified it can be used in this way. However it can work to treat this particular condition.

How do I take the medicine?

For the treatment of cataplexy, fluoxetine should be taken once a day, in the morning. Fluoxetine may be taken with or without food.

Keep taking the medicine until your doctor tells you not to. Stopping suddenly can cause problems and your doctor will want you to reduce your dose gradually if you need to stop treatment.

What should I do if I forget to take the medicine?

Do not take a double dose to make up for a missed dose as this is too much to take at one time.

If you forget to take the dose in the morning, don’t worry and take it as soon as you remember.

Try not to take fluoxetine within the 2 hours before your bedtime as your sleep may be disrupted. In this case, do not take the dose and wait until the next morning for your usual dose.

Missing a dose of fluoxetine can cause severe cataplexy attacks.

Are there any side effects?

Most medicines can cause unwanted side effects, although not everyone gets them. The following are examples of some of the side effects reported by patients taking fluoxetine. The unwanted effects often fade as your body adjusts to the new medicine. Speak with your GP or pharmacist if any of the following continue or become troublesome.

Side effect

What should I do if it happens?

Very common (more than 10 percent)
Feeling or being sick



Stick to simple foods – avoid rich or spicy foods.
Dry mouth Try chewing sugar-free gum or sucking sugar-free sweets.
Headache Drink plenty of water and take your usual painkiller, for example, paracetamol.
Common (between 1 percent and 10 percent)
Feeling restless or shaky These usually settle within a few days. If any becomes troublesome or severe, speak with your GP or consultant.
Feeling dizzy, tired or weak

Blurred vision

If this happens, do not drive or use tools or machinery until you feel better. Do not drink alcohol.
Flushing or sweating Take care not to become overheated during exercise or hot weather
Difficulty sleeping or yawning

Loss of appetite, or weight

Aches and pains

Reduced sexual drive or ability



Changes in taste

Difficulty in passing urine

If any of these become troublesome, speak with your GP.

For further information on side effects, please see the manufacturer’s leaflet that comes with the medicine.


If you experience any of the following symptoms, contact your GP for advice as soon as possible:

  • a rash or blisters on the skin
  • swelling on your face
  • difficulty breathing
  • any changes to your mood (such as feeling anxious, nervous or agitated)
  • behaviour, or thinking (feeling forgetful)
  • any suicidal thoughts, or thoughts about harming yourself

Can I take fluoxetine with other medicines?

Fluoxetine may interact with some medicines. It is important to let us know about any medicines that you are currently taking, so that we can check fluoxetine is suitable for you.

If you are buying any medicines over the counter from a pharmacy always mention that you have been prescribed fluoxetine. It is safe to take paracetamol with this medicine, but ask for advice before buying any anti-inflammatory painkillers such as ibuprofen or aspirin.


Seek advice when purchasing herbal or homeopathic remedies. In particular, do not take the herbal remedy St John’s wort.

How will my treatment be reviewed?

Your treatment will be reviewed on an ongoing basis in the Narcolepsy Clinic and the dose adjusted in response to your symptoms. Your consultant will want to check to make sure that the treatment is helping. You may need to have your blood pressure and heart rate checked regularly.

How do I get a repeat prescription?

Your GP will give you a repeat prescription for fluoxetine. Please make sure you request your repeat prescription early to help stop you running out or risk missing any doses of your medication.

If your GP won’t supply your fluoxetine, your consultant will provide repeat prescriptions, which will be sent in the post.

It can also be dispensed by the Rowland’s pharmacy at Sheffield Children’s Hospital outpatients on 0114 305 3367.

Is there anything else I need to know?

It can take 1 or 2 weeks after starting this treatment before the effect builds up, and up to 4 weeks before you feel the full benefit. It is important that you continue taking it, even if you think it is not helping.

You may have distressing thoughts while taking fluoxetine (especially if you are depressed), and think about harming yourself or ending your life. If this happens, it is very important that you tell your doctor about it as soon as possible.


Fluoxetine can make your skin more sensitive to sunlight. You should try to avoid strong sunlight, and use a sun cream with a high protection factor.

❌ Do not use sunbeds.


Fluoxetine can alter the levels of sugar in your blood. If you have diabetes you may need to check your blood sugar more regularly. Your GP can advise you about this.


❌ Do not drink alcohol while taking fluoxetine as it may increase symptoms of depression or anxiety, cause increased dizziness, drowsiness or co-ordination issues.


If you are old enough to drive, you must let the Driver and Vehicle Licensing Authority (DVLA) know if you are diagnosed with narcolepsy.

You may be allowed to drive again when your symptoms are well controlled with medication, but you will need to have regular reviews. Your consultant will advise you about this.

If you are a driver, please be aware that fluoxetine may affect your reactions and ability to drive. It is an offence to drive while your reactions are impaired. Even if your driving ability is not impaired, if you drive, you should carry some evidence with you which shows that the medicine has been prescribed for you. A repeat prescription form or the patient information leaflet from the packet is generally enough.

Pregnancy and breastfeeding 

❌ We do not recommend the use of this medicine if you are pregnant or breastfeeding.

You should let your consultant know if you are planning a pregnancy so that a management plan can be agreed. If you discover that you are pregnant, please contact your consultant for advice as soon as possible.

Sleep routine 

Taking fluoxetine is not a replacement for a good sleep routine. It is still important to aim to get around 9 to 11 hours of sleep at night, depending on your age. Try to go to bed when you’re tired and get up at about the same time each day.

Fluoxetine should be kept out of reach of children. If anyone other than you takes this medicine, you, they or their parent or carer should contact NHS 111 for advice. If they are unwell then they should call for an ambulance.


Do not use the medicine after the expiry date.

The expiry date is printed on the container. Any that have gone out of date should be returned to your local pharmacy to be properly disposed of.

Contact us

Medicines Helpline

If you have any questions or concerns about your medicines, please speak to the staff caring for you or call our pharmacy helpline.

Narcolepsy team secretaries

0114 271 7400 between 9am to 5pm, Monday to Friday.

Rowland’s Outpatient pharmacy

0114 305 3367 between 9am to 5pm, Monday to Friday.

Your comments and concerns

For advice, support or to raise a concern, contact our Patient Advice and Liaison Service (PALS) on 0114 271 7594 or email scn-tr.pals@nhs.net.
To make a complaint, contact the complaints department on 0114 271 7194.

Other resources

Narcolepsy UK
You might find this charity’s website useful for connecting with patients who suffer from the same condition as you, but any information found should not alter your current treatment. You should discuss any new advice with the doctor caring for your condition.

NHS 111
Offers medical help and advice from fully trained advisers supported by experienced nurses and paramedics. Available over the phone 24 hours a day on 111.

Provides online information and guidance on all aspects of health and healthcare, to help you make choices about your health.


Reproduced with the kind permission of Guy’s and St Thomas’ NHS Foundation Trust.

Is something missing from this resource that you think should be included? Please let us know

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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: SLP31

Resource Type: Article

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