Skip to main content

Fenfluramine Side Effects

Medically reviewed by Drugs.com. Last updated on Sep 3, 2021.

For the Consumer

Applies to fenfluramine: oral solution

Warning

Do not use this medicine if you have used an MAO inhibitor in the past 14 days, such as isocarboxazid, linezolid, methylene blue injection, phenelzine, rasagiline, selegiline, or tranylcypromine.

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 this medicine 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.

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 may include:

  • 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.

For Healthcare Professionals

Applies to fenfluramine: oral solution, oral tablet

General

The more commonly reported adverse effects have included decreased appetite and weight, somnolence, sedation, lethargy, diarrhea, constipation, increased blood pressure, and gait disturbances.[Ref]

Cardiovascular

Very common (10% or more): Abnormal echocardiogram (up to 23%), increased blood pressure (up to 13%)

Common (1% to 10%): Increased heart rate[Ref]

Abnormal echocardiogram included trace and mild mitral regurgitation, and trace aortic regurgitation, which are considered physiologic. Valvular heart disease and pulmonary arterial hypertension were evaluated in the clinical studies via echocardiography for up to 3 years in duration and no patient developed findings consistent with either condition. During the open-label extension study, trace mitral regurgitation and trace aortic regurgitation were reported in 14% and 0.4%, respectively. Trace and mild mitral regurgitation, and trace aortic regurgitation are

considered physiologic in the absence of structural valve abnormalities.[Ref]

Nervous system

Very common (10% or more): Somnolence, sedation, and lethargy (26%)

Common (1% to 10%): Ataxia, balance disorder, gait disturbance, hypotonia, falls, headache, status epilepticus, stereotypy, tremor[Ref]

Metabolic

Very common (10% or more): Decreased appetite (up to 49%), decreased weight (up to 13%)

Common (1% to 10%): Dehydration, decreased blood glucose[Ref]

This drug decreases appetite and causes dose-related weight loss. In clinical studies, decreased appetite and weight were reported in 37% and 9%, respectively (placebo=8% and 1%). Weight loss of 7% or greater from baseline was reported in 19% of patients treated with this drug compared to 2% of patients on placebo.[Ref]

Psychiatric

Common (1% to 10%): Abnormal behavior, insomnia, irritability, negativism[Ref]

Genitourinary

Common (1% to 10%): Urinary incontinence, enuresis, urinary tract infection[Ref]

Respiratory

Very common (10% or more): Upper respiratory infections (up to 21%)

Common (1% to 10%): Bronchitis, croup, rhinitis, laryngitis[Ref]

Other

Very common (10% or more): Fatigue, malaise, and asthenia (up to 30%), pyrexia (up to 21%)

Common (1% to 10%): Chills, decreased activity, contusion, ear infection[Ref]

Dermatologic

Common (1% to 10%): Rash, eczema[Ref]

Endocrine

Common (1% to 10%): Blood prolactin increase[Ref]

Gastrointestinal

Very common (10% or more): Diarrhea (up to 31%), drooling and/or salivary hypersecretion (up to 13%)

Common (1% to 10%): Constipation, gastroenteritis, vomiting[Ref]

Musculoskeletal

Common (1% to 10%): Hypotonia[Ref]

Ocular

Very common (10% or more): Glaucoma[Ref]

Frequently asked questions

References

1. "Product Information. Fintepla (fenfluramine)." Zogenix, Inc, San Diego, CA.

Further information

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

Some side effects may not be reported. You may report them to the FDA.