fenfluramine hydrochloride at a glance
Medicine class
Other antiseizure treatment; serotonin-releasing agent
Licensed role
Add-on treatment for seizures associated with Dravet syndrome or Lennox–Gastaut syndrome
How it is supplied
Oral solution measured with the supplied oral syringe
Important monitoring
Regular echocardiograms and monitoring of appetite and weight are required
What is fenfluramine hydrochloride used for?
UK-licensed uses are:
Add-on treatment for seizures associated with Dravet syndrome in people aged 2 years and over.
Add-on treatment for seizures associated with Lennox–Gastaut syndrome in people aged 2 years and over.
How does fenfluramine hydrochloride work?
It releases serotonin and acts at several serotonin receptors and the sigma-1 receptor. These actions may reduce seizures, although the precise mechanism is not fully established.
fenfluramine hydrochloride preparations and strengths
Oral solution
Route: Oral
Strengths: 2.2 mg/mL
How to take fenfluramine hydrochloride
The oral solution may be taken with or without food and is compatible with a ketogenic diet and most gastric or nasogastric feeding tubes.
Measure it only with the supplied oral syringe.
Place the syringe tip against the inside of the cheek and press the plunger gently; do not aim towards the back of the throat.
Rinse the syringe and plunger with cold water, then air-dry. Do not use detergent or a dishwasher.
Leave the bottle adaptor in place after fitting it.
Record the opening date. Do not refrigerate or freeze the solution.
fenfluramine hydrochloride side effects
Common or expected effects
- Reduced appetite or weight loss
- Sleepiness, tiredness or lethargy
- Diarrhoea, vomiting or constipation
- Behaviour or mood changes, agitation or insomnia
- Poor coordination, reduced muscle tone or tremor
- Increased saliva
- Rash
Get urgent medical advice
- Serotonin syndrome
- Heart-valve disease or pulmonary arterial hypertension
- A prolonged seizure or important increase in seizure frequency
- Sudden reduced vision or eye pain suggesting angle-closure glaucoma
- Serious allergic reaction or bronchospasm
- New thoughts of self-harm or suicide
fenfluramine hydrochloride in pregnancy
Human pregnancy information is limited, so UK product information advises avoiding fenfluramine during pregnancy as a precaution. Seek prompt specialist advice if pregnant, possibly pregnant or planning pregnancy; do not alter treatment without prescriber guidance.
fenfluramine hydrochloride while breastfeeding
It is unknown whether fenfluramine or its metabolites pass into human milk, and risk to the child cannot be excluded. A specialist should weigh the benefit of breastfeeding against the benefit of continuing treatment.
fenfluramine hydrochloride interactions
A full medicines review is needed before treatment and whenever another medicine is started or stopped.
Monoamine oxidase inhibitors (MAOIs)
Concurrent or recent use is contraindicated because of serotonin syndrome risk.
SSRIs, SNRIs, tricyclic antidepressants, triptans and serotonergic antipsychotics
Combined serotonergic effects increase the risk of potentially life-threatening serotonin syndrome.
Alcohol and other central nervous system depressants
These can worsen sleepiness and impaired alertness.
Common questions about fenfluramine hydrochloride
Answers are fully visible for fast scanning and source review.
What is fenfluramine hydrochloride used for?
It is added to other antiseizure treatments for seizures associated with Dravet syndrome or Lennox–Gastaut syndrome in people aged 2 years and over.
Is fenfluramine hydrochloride used on its own?
Its UK licence is as an add-on to other antiseizure medicines, not as sole treatment.
Why are heart scans needed?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.