Fintepla Side Effects: What to Expect and When to Call Your Doctor

Fintepla (fenfluramine) is a highly effective antiseizure medication, but like all medications it comes with side effects. Some are common and manageable; others are serious and require immediate medical attention. This guide covers everything patients and caregivers need to know about Fintepla's side effect profile.

Fintepla's Boxed Warning: Cardiac Risks

The most serious concern with Fintepla is its boxed warning (the FDA's most serious warning level) for:

Valvular heart disease (VHD): damage to heart valves

Pulmonary arterial hypertension (PAH): high blood pressure in the lung arteries

This warning comes from fenfluramine's history as a weight-loss drug in the 1990s, when high doses were linked to these conditions. At the doses used for epilepsy treatment, clinical trials of up to 3 years found no cases of VHD or PAH. However, because the risk cannot be entirely ruled out, the FINTEPLA REMS program requires echocardiograms before, during (every 6 months), and after treatment.

Symptoms to watch for that could suggest cardiac problems: shortness of breath, unusual fatigue, chest pain, swollen legs or ankles, rapid or irregular heartbeat. Call your doctor immediately if any of these develop.

Common Side Effects in Dravet Syndrome Patients

The following side effects occurred in at least 10% of Dravet syndrome patients in clinical trials (and more often than in the placebo group):

Decreased appetite (37% of patients) — monitor weight carefully, especially in children

Somnolence/sedation/lethargy — drowsiness, especially early in treatment

Diarrhea

Constipation

Fatigue, malaise, weakness

Ataxia, balance problems, or gait disturbance — unsteady walking

Blood pressure increase — monitor BP at follow-up visits

Drooling/excess saliva

Fever (pyrexia)

Upper respiratory tract infection

Vomiting

Decreased weight — monitor growth in pediatric patients

Common Side Effects in Lennox-Gastaut Syndrome (LGS) Patients

The side effect profile in LGS patients was slightly different. The most common side effects (≥10% and more common than placebo) were:

Diarrhea

Decreased appetite

Fatigue

Somnolence (drowsiness)

Vomiting

Serious Side Effects: When to Call Your Doctor Immediately

Serotonin Syndrome

Serotonin syndrome is a potentially life-threatening condition that can occur when Fintepla is taken with other serotonergic medications (SSRIs, SNRIs, MAOIs, TCAs, triptans). Symptoms include: mental status changes (hallucinations, agitation, coma), rapid heartbeat, high blood pressure, tight muscles, high body temperature, nausea, vomiting, diarrhea, and trouble walking. Call 911 or seek emergency care immediately if these occur.

High Blood Pressure (Hypertension)

Fintepla can cause blood pressure to increase, even in patients with no prior history of hypertension. In rare cases, a hypertensive crisis has been reported. Blood pressure should be monitored regularly. Contact your doctor if BP rises above your normal range.

Glaucoma

Fintepla can cause mydriasis (pupil dilation) and may trigger angle closure glaucoma. Symptoms include red eyes, eye pain, blurred vision, seeing halos around lights, nausea, or sudden vision changes. Seek immediate eye care if these occur.

Suicidal Thoughts or Behavior

As with all antiepileptic drugs (AEDs), Fintepla carries a class warning for increased risk of suicidal thoughts or behavior. Monitor for any changes in mood, depression, or unusual behavior and contact your doctor promptly if concerns arise.

Managing Side Effects at Home

Decreased appetite/weight loss: Offer small, nutrient-dense meals more frequently. Track weight weekly in pediatric patients and report significant changes to your doctor.

Drowsiness: Avoid driving or operating machinery until you know how Fintepla affects you. Drowsiness often improves after the first few weeks.

Do not stop abruptly: Always taper Fintepla gradually under medical supervision. Abrupt discontinuation can trigger increased seizures or status epilepticus.

For more on drug interactions with Fintepla, read Fintepla Drug Interactions: What to Avoid. And if you're struggling to fill your prescription, medfinder can help locate a certified pharmacy near you.