Fenfluramine Side Effects
Medically reviewed by Drugs.com. Last updated on Feb 16, 2023.
Applies to fenfluramine: oral solution.
Valvular Heart Disease and Pulmonary Arterial Hypertension (PAH)
- Serotonergic drugs with 5-HT2B receptor agonist activity, including fenfluramine, have been associated with valvular heart disease and PAH.1 7 11 13 (See Valvular Heart Disease and Pulmonary Arterial Hypertension under Cautions.)
- Echocardiographic assessments are required prior to initiation of therapy, during treatment, and after drug is discontinued.1
- Available only through a restricted distribution program.1 (See Restricted Distribution Program under Dosage and Administration.)
FDA approved a REMS for fenfluramine to ensure that the benefits outweigh the risks. The REMS may apply to one or more preparations of fenfluramine and consists of the following: elements to assure safe use and implementation system. See the FDA REMS page ([Web]).
Side effects include:
Decreased appetite, somnolence, sedation, lethargy, diarrhea, constipation, abnormal echocardiogram, fatigue, malaise, asthenia, ataxia, balance disorder, gait disturbance, increased BP, drooling, salivary hypersecretion, pyrexia, upper respiratory tract infection, vomiting, decreased weight, falls, status epilepticus.
For Healthcare Professionals
Applies to fenfluramine: oral solution, oral tablet.
The more commonly reported adverse effects have included decreased appetite and weight, somnolence, sedation, lethargy, diarrhea, constipation, increased blood pressure, and gait disturbances.[Ref]
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]
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]
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]
Common (1% to 10%): Abnormal behavior, insomnia, irritability, negativism[Ref]
Common (1% to 10%): Urinary incontinence, enuresis, urinary tract infection[Ref]
Very common (10% or more): Upper respiratory infections (up to 21%)
Common (1% to 10%): Bronchitis, croup, rhinitis, laryngitis[Ref]
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]
Common (1% to 10%): Rash, eczema[Ref]
Common (1% to 10%): Blood prolactin increase[Ref]
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]
Common (1% to 10%): Hypotonia[Ref]
Very common (10% or more): Glaucoma[Ref]
Frequently asked questions
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More about fenfluramine
Related treatment guides
1. "Product Information. Fintepla (fenfluramine)." Zogenix, Inc (2020):
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.