Fenfluramine is the generic name (non-brand name) of a seizure medicine with the brand name Fintepla® from Zogenix.

Fenfluramine is approved for use:

  • In the US, the FDA has approved fenfluramine to treat seizures associated with Dravet syndrome and Lennox-Gastaut syndrome in persons 2 years of age and older.


2.2 mg/mL

Fenfluramine is usually started at a dose of 0.2 mg/kg/day divided into 2 equal doses and may be increased by 0.2 mg/kg/d every 4 days to a maximum dose of 0.7 mg/kg/d (maximum 25.9 mg/day).  

The dose should be reduced in patients on stiripentol, as co-therapy with stiripentol increases the blood levels of fenfluramine. If using with stiripentol, the fenfluramine should be started at 0.2 mg/kg/d and increased gradually as needed over approximately 3 weeks to a maximum dose of 0.4 mg/kg/day (to a maximum 17 mg/day). 

Follow your prescribing provider's instructions for how much to take and when to make changes.  


Updated: 17/10/2023

Brand Name(s)


Used to Treat

Dravet Syndrome
Lennox-Gastaut Syndrome


Package Insert

Frequently Asked Questions

    How to take and store Fenfluramine?

    How To Take:

    Take fenfluramine exactly as your healthcare provider prescribes it. Do not change your dose without talking to your provider first. Stopping a seizure medicine suddenly can cause seizures that will not stop (status epilepticus).

    Fenfluramine is usually taken 2 times a day. Always use an accurate measuring spoon or syringe to make sure the amount is correct. Do not use a regular teaspoon.

    Fenfluramine is best taken with food to reduce the chance of stomach upset.

    Take only the amount that your provider tells you to take. If you take an extra dose, call your provider for advice. If you take a larger amount or overdose, call the poison control center (800-222-1222) or call your hospital emergency room.

    Ensure your healthcare provider knows what other medications are being taken together with fenfluramine. Other medications used to treat behavior, mood, or sleep problems may affect serotonin levels in the brain. Use of these medications together with fenfluramine can increase the risk of a potentially serious reaction called serotonin syndrome. Symptoms of serotonin syndrome include confusion, agitation, increased heart rate or blood pressure, tremor, muscle stiffness or twitching, fever, and diarrhea.

    How To Store:

    Store at room temperature (below 86oF, 30oC).

    Keep away from light and moisture.

    Keep all medicines out of reach of children.

    What if I forget?

    Taking the right amount of seizure medicine on time every day is the most important way to control seizures. Try these steps to help you remember when to take fenfluramine.

    • If you miss a dose, take it as soon as you remember it.
    • If it is almost time for the next dose, check with your health care provider for advice.
    • To avoid missed doses, set an alarm on your watch or on phone.
    • Use an app or seizure diary to reminder you of when to take medicines.
    • Write down any missed doses in your seizure calendar. Share this with your healthcare provider at each visit.
    How does Fenfluramine affect the brain?

    Brain cells normally talk to each other using electrical signals and chemicals. Fenfluramine works by binding to serotonergic receptors, as well as by positively modulating a receptor called sigma 1, which itself further modulates how brain cells communicate with each other. Exactly how this reduces seizures is not clearly known. 

    What are the most common side effects of Fenfluramine?
    • Decreased appetite
    • Diarrhea
    • Weight loss
    • Feeling tired or sleepy

    Previously, fenfluramine was used in much higher doses, and in combination with another medication called phentermine for weight loss. This combination was associated with heart problems including abnormalities of the heart valves and pulmonary hypertension. Importantly, clinical trials of fenfluramine have not found any heart problems, when fenfluramine is used at the doses prescribed. However, persons taking fenfluramine should undergo regular heart follow-up with echocardiograms. 

    Suicidal thoughts and behavior: In 2008, the Food and Drug Administration (FDA) reviewed data from drug studies that showed a possible relationship between many seizure medicines and suicidal thoughts and behavior. Together, these thoughts and behavior are called suicidality. According to the FDA’s Alert, among the patients with epilepsy in these drug studies, more had symptoms of suicidality than people taking a placebo or inactive substance - 3.5 of 1,000 people taking a seizure medicine had suicidality compared to 1 of 1,000 people taking a placebo. Such behavior is possible but rare with fenfluramine. 

    What are the dose ranges for Fenfluramine?

    The best amount of any seizure medicine is the amount that controls seizures without causing bothersome side effects. This depends on many factors, which are different for every individual. 

    The maximum dose for persons not taking stiripentol is 0.7 mg/kg/d (maximum of 25.9 mg/day) and for those taking stiripentol is 0.4 mg/kg/d (maximum 17 mg/day). 

    Blood levels are not typically monitored for fenfluramine. 


    Primary Generalized Epilepsy

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