Fenfluramine Dosage

Medically reviewed by Drugs.com. Last updated on Jan 31, 2025.

Applies to the following strengths: 20 mg; 2.2 mg/mL

Usual Adult Dose for Lennox-Gastaut Syndrome

Dravet Syndrome:
Initial and maintenance dose: 0.1 mg/kg orally 2 times a day

May increase dose weekly for further reduction of seizures; dose increases are based on concomitant therapy, efficacy, and tolerability:

For Patients NOT on concomitant stiripentol who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.2 mg/kg orally 2 times a day
On Day 14: May increase to a maximum recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.15 mg/kg orally 2 times a day
On Day 14: May increase to 0.2 mg/kg orally 2 times a day

Maximum Dose: 17 mg/day

Lennox-Gastaut Syndrome:
Initial dose: 0.1 mg/kg orally 2 times a day
Dosage should be increased weekly based on tolerability.

For Patients NOT on concomitant stiripentol who are tolerating this drug well:

Should titrate to the recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well:

Should titrate to the recommended maintenance dosage of 0.2 mg/kg orally 2 times a day

Maximum Dose: 17 mg/day

Comments:

For patients NOT on concomitant stiripentol for whom a more rapid titration is warranted, the dose may be increased every 4 days.
This drug should normally be gradually withdrawn to reduce the potential for increased seizure frequency and status epilepticus. Should not be discontinued without consulting with the healthcare provider.

Use: For the treatment of seizures associated with Dravet syndrome or Lennox-Gastaut syndrome

Usual Adult Dose for Dravet Syndrome

Dravet Syndrome:
Initial and maintenance dose: 0.1 mg/kg orally 2 times a day

May increase dose weekly for further reduction of seizures; dose increases are based on concomitant therapy, efficacy, and tolerability:

For Patients NOT on concomitant stiripentol who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.2 mg/kg orally 2 times a day
On Day 14: May increase to a maximum recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.15 mg/kg orally 2 times a day
On Day 14: May increase to 0.2 mg/kg orally 2 times a day

Should titrate to the recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well:

Should titrate to the recommended maintenance dosage of 0.2 mg/kg orally 2 times a day

Maximum Dose: 17 mg/day

Comments:

For patients NOT on concomitant stiripentol for whom a more rapid titration is warranted, the dose may be increased every 4 days.
This drug should normally be gradually withdrawn to reduce the potential for increased seizure frequency and status epilepticus. Should not be discontinued without consulting with the healthcare provider.

Use: For the treatment of seizures associated with Dravet syndrome or Lennox-Gastaut syndrome

Usual Pediatric Dose for Lennox-Gastaut Syndrome

Age: 2 years and older:
Dravet Syndrome:
Initial and maintenance dose: 0.1 mg/kg orally 2 times a day

May increase dose weekly for further reduction of seizures; dose increases are based on concomitant therapy, efficacy, and tolerability:

For Patients NOT on concomitant stiripentol who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.2 mg/kg orally 2 times a day
On Day 14: May increase to a maximum recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.15 mg/kg orally 2 times a day
On Day 14: May increase to 0.2 mg/kg orally 2 times a day

Should titrate to the recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well:

Should titrate to the recommended maintenance dosage of 0.2 mg/kg orally 2 times a day

Maximum Dose: 17 mg/day

Comments:

For patients NOT on concomitant stiripentol for whom a more rapid titration is warranted, the dose may be increased every 4 days.
This drug should normally be gradually withdrawn to reduce the potential for increased seizure frequency and status epilepticus. Should not be discontinued without consulting with the healthcare provider.

Use: For the treatment of seizures associated with Dravet syndrome or Lennox-Gastaut syndrome in pediatric patients 2 years of age and older.

Usual Pediatric Dose for Dravet Syndrome

Age: 2 years and older:
Dravet Syndrome:
Initial and maintenance dose: 0.1 mg/kg orally 2 times a day

May increase dose weekly for further reduction of seizures; dose increases are based on concomitant therapy, efficacy, and tolerability:

For Patients NOT on concomitant stiripentol who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.2 mg/kg orally 2 times a day
On Day 14: May increase to a maximum recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well at 0.1 mg/kg twice daily and require further reduction of seizures:

On Day 7: May increase to 0.15 mg/kg orally 2 times a day
On Day 14: May increase to 0.2 mg/kg orally 2 times a day

Should titrate to the recommended maintenance dosage of 0.35 mg/kg orally 2 times a day

Maximum Dose: 26 mg/day

For Patients ON concomitant stiripentol and clobazam who are tolerating this drug well:

Should titrate to the recommended maintenance dosage of 0.2 mg/kg orally 2 times a day

Maximum Dose: 17 mg/day

Comments:

For patients NOT on concomitant stiripentol for whom a more rapid titration is warranted, the dose may be increased every 4 days.
This drug should normally be gradually withdrawn to reduce the potential for increased seizure frequency and status epilepticus. Should not be discontinued without consulting with the healthcare provider.

Use: For the treatment of seizures associated with Dravet syndrome or Lennox-Gastaut syndrome in pediatric patients 2 years of age and older.

Renal Dose Adjustments

Mild and Moderate Renal Dysfunction: No adjustment recommended
Severe Renal Dysfunction: A maximum total daily dosage of 20 mg without concomitant stiripentol and 17 mg with concomitant stiripentol plus clobazam is recommended.

Liver Dose Adjustments

Mild Liver Dysfunction: A maximum total daily dosage of 20 mg without concomitant stiripentol and 13 mg with concomitant stiripentol plus clobazam is recommended.
Moderate Liver Dysfunction: A maximum total daily dosage of 20 mg without concomitant stiripentol is recommended. Use is not recommended with concomitant stiripentol plus clobazam.
Severe Liver Dysfunction: A maximum total daily dosage of 17 mg without concomitant stiripentol is recommended. Use is not recommended with concomitant stiripentol plus clobazam.

Dose Adjustments

Concomitant Use of Strong CYP450 1A2 or CYP450 2D6 Inhibitors:

Maximum total daily dosage of 20 mg without concomitant stiripentol and 17 mg with concomitant stiripentol plus clobazam is recommended.

Elderly: Clinical studies did not include patients 65 years of age and over. Dose selection for an elderly patient should be cautious, starting at the low end of the dosing range.

Precautions

The US FDA requires a Risk Evaluation and Mitigation Strategy (REMS) for this drug. It includes a communication plan, elements to assure safe use, and an implementation system. For additional information go to: www.accessdata.fda.gov/scripts/cder/rems/index.cfm

US BOXED WARNINGS:

There is an association between serotonergic drugs with 5-HT2B receptor agonist activity; including fenfluramine, and valvular heart disease and pulmonary arterial hypertension.
Echocardiogram assessments are required before, during, and after treatment; the benefits versus the risks of initiating or continuing therapy must be considered, based on echocardiogram findings.
Because of the risks of valvular heart disease and pulmonary arterial hypertension, this drug is available only through a restricted program under a REMS called the FINTEPLA REMS

CONTRAINDICATIONS:

Hypersensitivity to any of the ingredients
Concomitant use, or within 14 days of the administration of monoamine oxidase inhibitors due to an increased risk of serotonin syndrome

To monitor the outcomes of pregnant women exposed to this drug, a pregnancy registry has been established. Patients are encouraged to register in the North American Antiepileptic Drug (NAAED) Pregnancy Registry by visiting http://www.aedpregnancyregistry.org.

Safety and efficacy have not been established in patients younger than 2 years old.

Consult WARNINGS section for additional precautions.

US Controlled Substance: Schedule IV

Dialysis

Data not available

Other Comments

Administration advice:

Administer orally with or without food using a calibrated measuring device; a household teaspoon or tablespoon is not an adequate measuring device.
This drug is compatible with commercially available gastric and nasogastric feeding tubes.

Storage requirements:

Store at room temperature between 20C and 25C (68F to 77F); do not refrigerate or freeze
Discard any unused portion 3 months after first opening or the "discard after" date, whichever is sooner.

Preparation:

Before dispensing, the pharmacist will insert a press-in bottle adapter into the dispensed bottle.
The pharmacy will provide a 3 mL or 6 mL calibrated oral dosing syringe.

General:

This drug in tablet form was previously approved for the treatment of obesity but was removed from the market for causing adverse cardiac events.

Monitoring:

Prior to starting treatment, obtain an echocardiogram assessment to evaluate for valvular heart disease and pulmonary arterial hypertension; repeat every 6 months during treatment, and once more, 3 to 6 months after the final dose.
Monitor blood pressure
Monitor height and weight in pediatric patients
Monitor for somnolence, sedation, and lethargy
Monitor for emergence or worsening of depression and/or any unusual changes in mood or behavior.
To monitor the outcomes of pregnant women exposed to this drug, a pregnancy registry has been established. Patients can be registered with the North American Antiepileptic Drug (NAAED) Pregnancy Registry by visiting http://www.aedpregnancyregistry.org.

Patient advice:

Read the Patient Information and Instructions for Use.
This drug can cause somnolence, sedation, and lethargy. Be cautious about operating machinery and driving until you know how it will affect you.
Contact immediately your health care provider if you have new or worsening symptoms of depression, unusual changes in mood or behavior, or new suicidal thoughts, behavior, or thoughts of self-harm.
Do not discontinue this drug without consulting your health care provider. Withdrawal should be gradual to reduce the risk of seizures.
Contact your healthcare provider if you have changes in your vision or ocular pain.
Female patients: Notify your health care provider if you become pregnant while taking this drug or intend to become pregnant. You will need to enroll in a pregnancy registry assessing the safety of this drug during pregnancy.