fenfluramine

Score breakdown (68/100)

Safety: 75

• Listed by the independent review Prescrire as a drug to avoid (2026 edition) (-10)
• Subject to a REMS safety program: FDA requires special controls to use it (-10)
• Death share in reports is near or below the FAERS average (0.3x)
• Off-label use is among the five most-reported items: widely used beyond its approved evidence (-5)

Evidence: 48

• 123 randomized trials and 11 systematic reviews/meta-analyses indexed in PubMed
• Prescrire's independent reviewers find its harm-benefit balance unfavourable versus alternatives (-10)
• No Cochrane review found (-5)

Regulatory history: 82

• No recalls on record since 2016
• REMS program in force (-10)
• 7 label changes approved since 2021: the safety story is still moving (-8)

Money & lawsuits: 70

• Pharma paid doctors $1,075,592 tied to this drug last year (-30)
• Not named in any pending federal MDL

Options: 70

• No generic version approved: brand-only pricing (-30)
• 10 same-class alternatives exist

Independent reviews and post-approval warnings

Prescrire: drug to avoid

Fenfluramine is an amphetamine authorised as an add-on to antiepileptic therapy in Dravet syndrome and Lennox-Gastaut syndrome, two rare and serious forms of infantile epilepsy. Despite a decrease in the overall frequency of seizures, fenfluramine appears to increase the incidence of convulsive status epilepticus. Fenfluramine can provoke heart valve disease and pulmonary arterial hypertension, which is why its use as an appetite suppressant was discontinued. It can also cause neuropsychiatric disorders and other cardiovascular disorders (Prescrire Int n° 233, 263).

Prescrire is a French independent review funded only by subscribers, with no industry money. Its annual "drugs to avoid" list (2026 edition, section: Infectious diseases) names drugs it judges more harmful than useful in every authorised indication. Its view is one expert opinion, reached without a conflict of interest.

What the FDA label says

Approved uses

Not available.

Contraindications

None listed.

Source: FDA SPL label, effective .

Side-effect reports sent to the FDA

These are counts of reports people filed, not rates of harm. Anyone can file one, and nobody checks whether the drug was the cause. Millions of doses are taken for every report sent, so the useful part is how this drug compares with the average across all drugs.

Problems reported most often

Reports per year

Source: the FDA's Adverse Event Reporting System (FAERS). Reports are voluntary and unverified. Drugs that are prescribed a lot, in the news, or in lawsuits attract more reports, so the percentages are compared with the whole database to correct for that partly, not fully.

Recalls and regulatory record

Evidence base

Counts measure how much evidence exists and how transparent it is, not how big the benefit is. For that, ask your prescriber: if 100 people like me took this, how many would get better because of it, and how many would be harmed? (Doctors call these the "number needed to treat" and "number needed to harm.") It differs by condition and is the number drug ads leave out. Sources: PubMed, ClinicalTrials.gov.

Money and lawsuits

In 2024, drug companies reported $1,075,592 in payments to US physicians and hospitals tied to this drug across 8,633 transactions (Fintepla $1,075,592).

No pending federal MDL names this drug or its brands.

Not named in any federal pharmaceutical settlement of $100M or more on record.

Sources: CMS Open Payments (Sunshine Act); Judicial Panel on Multidistrict Litigation pending docket list; DOJ settlements as tabulated on Wikipedia with links to the primary record. State-court and individual suits are not included.

Who takes it and what it costs

Same-class alternatives

1 drug in the same class grades a letter or more higher than fenfluramine on this site. Worth asking whether one of them would do the same job for you.

Same ATC pharmacological class, graded ones first, best grade at the top. Being in the same class does not make them interchangeable for your condition; it makes them worth asking about.

Questions to ask your prescriber

1. An independent reviewer (Prescrire) lists this as a drug to avoid because the harms outweigh the benefits versus alternatives. What is your view on that?
2. This drug has a REMS safety program. What monitoring does that require from us?
3. The most-reported problems in FDA's adverse event data are seizure, tricuspid valve incompetence. How would we recognize and handle those?
4. Off-label use is among the most-reported items for this drug. Is my use on-label, and if not, what evidence supports it?
5. Why this one over cathine, clobenzorex, dexfenfluramine? What would make you pick one of those instead?
6. There is no generic. Is there an older generic in the same class that works as well for my situation?
7. The manufacturer pays physicians heavily to promote this drug. Have you received anything from them?
8. What result are we expecting, by when, and what is the plan if it does not happen?
9. If 100 people like me took this drug, how many would actually get better because of it, and how many would be harmed by it? (Doctors call these the number needed to treat and the number needed to harm.)