Fenfluramine (fen FLUR a meen) has been approved by the FDA to treat seizures associated with Dravet syndrome in patients 2 years of age and older.

Your epilepsy treatment should always be discussed with your healthcare provider before use. Based on their judgment and knowledge, a drug may be prescribed for other epilepsy types not included in the indications. For more information, please see the prescribing information.

How can you take fenfluramine? (Available formulations)

Fenfluramine is available as an oral solution taken with or without food.

Who should not take fenfluramine?

If you are allergic to fenfluramine or any of the inactive ingredients, then you should not take it. Fenfluramine should not be taken within 14 days of the administration of monoamine oxidase inhibitors due to an increased risk of serotonin syndrome.

Other considerations may influence whether you should take fenfluramine. Tell your healthcare provider if you:

  • have or have had depression, mood problems, or suicidal thoughts or behavior.
  • have liver problems.
  • have heart problems.
  • have kidney problems.
  • have or have had weight loss.
  • are pregnant or plan to become pregnant.
  • are breastfeeding or plan to breastfeed.

What is important to know about taking fenfluramine?

Do not stop taking fenfluramine suddenly unless directed to do so by your healthcare provider.

As with all antiseizure medications, fenfluramine should be withdrawn gradually to minimize the risk of causing or worsening seizures or status epilepticus. You should not stop using fenfluramine suddenly unless your healthcare provider tells you to stop the medicine because of a serious side effect.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Taking fenfluramine with certain other medicines may cause side effects or affect how well they work. Do not start or stop other medicines without talking to your healthcare provider. Especially tell your healthcare provider if you take: monoamine oxidase inhibitors.

Boxed Warning

Fenfluramine is approved by the FDA because it is safe and effective for the majority of people who take it. However, there are risks associated with all medicines. Some side effects caused by fenfluramine can be very serious, and even life-threatening. It is important to be informed about these serious reactions and to be aware of their symptoms.

Valvular heart disease and pulmonary arterial hypertension

There is an association between drugs, including fenfluramine, that activates the serotonin 5-HT2B receptor (a protein on the outside membrane of a neuron), and valvular heart disease or pulmonary arterial hypertension (high blood pressure that affects the lungs and heart).

Echocardiogram assessments (evaluations for heart function and structure) are required before, during, and after treatment with fenfluramine. The benefits versus the risks of initiating or continuing fenfluramine must be considered, based on echocardiogram findings.

Because of the risks of valvular heart disease and pulmonary arterial hypertension, fenfluramine is available only through a restricted program under a Risk Evaluation and Mitigation Strategy (REMS) called the FINTEPLA REMS.

Women or those who are/plan to become pregnant
Use in pregnancy

At this time, there is not enough evidence regarding developmental risks associated with the use of fenfluramine in pregnant people. However, having a seizure during pregnancy could harm both the pregnant individual and the baby. Tell your healthcare provider right away if you become pregnant. Do not start or stop taking seizure medication during pregnancy without your healthcare provider’s advice.

If you become pregnant while taking fenfluramine, talk to your healthcare provider about registering with the North American Antiepileptic Drug (NAAED) Pregnancy Registry. The purpose of this registry is to collect information about the safety of antiseizure medicine during pregnancy. You can enroll in this registry by calling 1-888-233-2334.

Use during breastfeeding

There are no data on the presence of fenfluramine or its metabolites in human milk, the effects on the breastfed infant, or the effects on milk production. Talk to your healthcare provider about the risks. Your healthcare provider will consider the developmental and health benefits of breastfeeding along with your need for fenfluramine and the potential effect on the infant from fenfluramine or from your epilepsy.

What are the side effects of fenfluramine?

Common side effects

The most common side effects that were reported in studies of fenfluramine are decreased appetite; drowsiness (somnolence), sedation, lethargy; diarrhea; constipation; abnormal echocardiogram; fatigue, malaise, asthenia; problems with movement and balance (ataxia), balance disorder, gait disturbance; blood pressure increased; drooling, salivary hypersecretion (excessive saliva secretion); pyrexia (fever); upper respiratory tract infection; vomiting; decreased weight; fall and status epilepticus.

Rare, but serious side effects
Suicidal thoughts or behaviors

Studies have found that people who take antiseizure medications including fenfluramine may have suicidal thoughts or behaviors, which occur in approximately 1 in 500 patients. If you experience any thoughts or impulses to hurt yourself, you should contact your healthcare provider immediately.

Decreased appetite and decreased weight

Advise patients that fenfluramine can cause decreased appetite and decreased weight.

Somnolence, sedation, and lethargy

Fenfluramine can make you feel lethargic, sedated, or drowsy. Do not drive, operate heavy machinery, or do other dangerous activities until you know how fenfluramine affects you.

Do not drink alcohol or take other medicines that may make you sleepy while taking fenfluramine until you talk to your healthcare provider. Fenfluramine, when taken with alcohol or medicines that cause sleepiness, may make your sleepiness worse.

Do not drive or operate machinery until you have gained sufficient experience on fenfluramine to gauge whether it adversely affects your abilities.

Serotonin syndrome

Serotonin syndrome, a potentially life-threatening condition, may occur with fenfluramine, particularly if you also take fenfluramine and other serotonergic drugs with each other.

Increase in blood pressure

Monitor your blood pressure during treatment because elevated blood pressure has occurred even in patients without a history of hypertension.


You may develop angle-closure glaucoma if you take fenfluramine. Discontinue therapy if you experience an acute decrease in vision sharpness or eye pain.