Fenfluramine

Generic name: fenfluramine [ fen-FLUR-a-meen ]
Brand names: Fintepla, Pondimin
Dosage form: oral solution (2.2 mg/mL)
Drug classes: Anorexiants, CNS stimulants, Miscellaneous anticonvulsants

Medically reviewed by Drugs.com on Feb 10, 2023. Written by Cerner Multum.

What is fenfluramine?

Fenfluramine is used to treat seizures caused by Dravet syndrome and Lennox-Gastaut syndrome in people at least 2 years old.

Fenfluramine can cause serious side effects on your heart and lungs. fenfluramine is available only under a special program. You must be registered in the program and understand the risks and benefits of this medicine.

Fenfluramine may also be used for purposes not listed in this medication guide.

Fenfluramine side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Fenfluramine can cause serious side effects on your heart and lungs. Call your doctor right away if you have:

• chest pain, pounding heartbeats or fluttering in your chest;

• shortness or breath;

• blue colored skin or lips;

• swelling in your lower legs; or

• unusual tiredness or weakness, feeling like you might pass out.

Also call your doctor at once if you have:

• loss of appetite and weight loss;

• worsening seizures;

• blurred vision, tunnel vision, eye pain or redness, or seeing halos around lights;

• nausea or vomiting; or

• increased blood pressure--severe headache, blurred vision, pounding in your neck or ears, anxiety, nosebleed.

Seek medical attention right away if you have symptoms of serotonin syndrome, such as: agitation, hallucinations, fever, sweating, shivering, fast heart rate, muscle stiffness, twitching, loss of coordination, nausea, vomiting, or diarrhea.

Fenfluramine can affect weight or growth in children. Tell your doctor if your child is not growing at a normal rate while using this medicine.

Common side effects of fenfluramine may include:

• increased blood pressure;

• drowsiness;

• decreased weight;

• loss of appetite, vomiting, diarrhea, constipation;

• seizures that do not stop;

• feeling weak or tired;

• fever, infections;

• abnormal heart function tests;

• problems with balance, walking, or muscle movement;

• drooling; or

• cold symptoms such as stuffy nose, sneezing, sore throat.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Warnings

Do not use fenfluramine if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, and tranylcypromine. Wait at least 14 days after stopping an MAO inhibitor before you take fenfluramine.

Fenfluramine can cause serious side effects on your heart and lungs. Call your doctor at once if you have: chest pain, shortness of breath, unusual tiredness, swelling in your lower legs, fast or pounding heartbeats, blue skin or lips, or if you feel light-headed.

Fenfluramine may cause weight loss, which could affect growth in children. Weigh yourself regularly and tell your doctor if you lose weight. You may need to stop taking fenfluramine if you lose too much weight.

Avoid driving or hazardous activity until you know how fenfluramine will affect you. Your reactions could be impaired.

Some people have thoughts about suicide while taking fenfluramine. Stay alert to changes in your mood or symptoms. Report any new or worsening symptoms to your doctor.

Before taking this medicine

You should not use fenfluramine if you are allergic to it.

Do not use fenfluramine if you have used an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, tranylcypromine, and others.

Tell your doctor if you have ever had:

• heart problems;

• weight loss;

• depression, a mood disorder, or suicidal thoughts or actions;

• a drug or alcohol addiction; or

• liver or kidney disease.

Some people have thoughts about suicide while taking fenfluramine. Your doctor will need to check your progress at regular visits. Your family or other caregivers should also be alert to changes in your mood or symptoms.

Tell your doctor if you also use stimulant medicine, opioid medicine, herbal products, or medicine for depression, mental illness, Parkinson's disease, migraine headaches, serious infections, or prevention of nausea and vomiting. An interaction with fenfluramine could cause a serious condition called serotonin syndrome.

Tell your doctor if you are pregnant or breastfeeding.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of fenfluramine on the baby.

How should I take fenfluramine?

Your doctor will perform tests to make sure you do not have conditions that would prevent you from safely using fenfluramine.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Fenfluramine may be habit-forming. Misuse can cause addiction, overdose, or death. Keep the medication in a place where others cannot get to it. Selling or giving away fenfluramine is against the law.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

You may take fenfluramine with or without food.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Follow your care provider's instructions about giving fenfluramine through a feeding tube if needed.

Fenfluramine may cause decreased appetite and weight loss. Weigh yourself regularly and tell your doctor if you lose weight. You may need to stop taking fenfluramine if you lose too much weight. Weight loss may affect growth in children.

Your heart function will need to be checked using an electrocardiograph or ECG (sometimes called an EKG).

Store at room temperature away from moisture and heat. Do not refrigerate or freeze this medicine. Keep the bottle and syringe together in a clean area.

Keep track of your medicine. You should be aware if anyone is using it improperly or without a prescription.

Throw away any unused fenfluramine 3 months after you first opened the bottle or after the "discard" date on the label, whichever comes first.

Do not stop using fenfluramine suddenly, even if you feel fine. Stopping suddenly may cause increased seizures. Follow your doctor's instructions about tapering your dose.

Related/similar drugs

Zepbound, Wegovy, clonazepam, lamotrigine, Mounjaro, topiramate, semaglutide, Lamictal, Klonopin, phentermine

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking fenfluramine?

Avoid driving or hazardous activity until you know how fenfluramine will affect you. Your reactions could be impaired.

Avoid taking an herbal supplement containing St. John's wort.

What other drugs will affect fenfluramine?

Sometimes it is not safe to use certain medicines at the same time. Some drugs can affect your blood levels of other drugs you use, which may increase side effects or make the medicines less effective.

Tell your doctor about all your other medicines, especially:

• stiripentol; or

• clobazam.

This list is not complete. Other drugs may affect fenfluramine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Popular FAQ

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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