Formulary
Fenfluramine: Indications, Dosing, Side Effects and Interactions
Fenfluramine is a serotonin-releasing agent that stimulates multiple 5-HT receptor subtypes; this action on serotonin receptors in the brain may contribute to...
MedNext Academy | 4 min read
Fenfluramine: Indications, Dosing, Side Effects and Interactions
Fenfluramine is a serotonin-releasing agent that stimulates multiple 5-HT receptor subtypes; this action on serotonin receptors in the brain may contribute to...
Drug action
Fenfluramine is a serotonin-releasing agent that stimulates multiple 5-HT receptor subtypes; this action on serotonin receptors in the brain may contribute to its anti-seizure activity.
Indications and dose
**Adjunctive therapy of seizures associated with Dravet syndrome [without concomitant stiripentol] (under expert supervision)**
- **Adult** (By Mouth): Initially 0.1 mg/kg twice daily (max. per dose 13 mg) for 1 week, then increased if necessary to 0.2 mg/kg twice daily (max. per dose 13 mg) for 1 week, for patients who require more rapid titration the dose may be increased every 4 days; increased if necessary to 0.35 mg/kg twice daily (max. per dose 13 mg).
**Adjunctive therapy of seizures associated with Dravet syndrome [with concomitant stiripentol] (under expert supervision)**
- **Adult** (By Mouth): Initially 0.1 mg/kg twice daily (max. per dose 8.6 mg) for 1 week, then increased if necessary to 0.2 mg/kg twice daily (max. per dose 8.6 mg).
**Adjunctive therapy of seizures associated with Lennox-Gastaut syndrome (under expert supervision)**
- **Adult** (By Mouth): Initially 0.1 mg/kg twice daily (max. per dose 13 mg) for 1 week, then increased if tolerated to 0.2 mg/kg twice daily (max. per dose 13 mg) for 1 week, for patients who require more rapid titration the dose may be increased every 4 days, dose to be further increased if tolerated to the recommended maintenance dose; maintenance 0.35 mg/kg twice daily (max. per dose 13 mg).
**Adjunctive therapy of seizures associated with Dravet syndrome [without concomitant stiripentol] (under expert supervision) for fenfluramine**
- **Child 2-17 years** (By mouth): Initially 0.1 mg/kg twice daily (max. per dose 13 mg) for 1 week, then increased if necessary to 0.2 mg/kg twice daily (max. per dose 13 mg) for 1 week, for patients who require more rapid titration the dose may be increased every 4 days; increased if necessary to 0.35 mg/kg twice daily (max. per dose 13 mg).
**Adjunctive therapy of seizures associated with Dravet syndrome [with concomitant stiripentol] (under expert supervision) for fenfluramine**
- **Child 2-17 years** (By mouth): Initially 0.1 mg/kg twice daily (max. per dose 8.6 mg) for 1 week, then increased if necessary to 0.2 mg/kg twice daily (max. per dose 8.6 mg).
**Adjunctive therapy of seizures associated with Lennox-Gastaut syndrome (under expert supervision) for fenfluramine**
- **Child 2-17 years** (By mouth): Initially 0.1 mg/kg twice daily (max. per dose 13 mg) for 1 week, then increased if tolerated to 0.2 mg/kg twice daily (max. per dose 13 mg) for 1 week, for patients who require more rapid titration the dose may be increased every 4 days, dose to be further increased if tolerated to the recommended maintenance dose; maintenance 0.35 mg/kg twice daily (max. per dose 13 mg).
Cautions
History of anorexia nervosa; history of bulimia nervosa
Contraindications
Pulmonary arterial hypertension; valvular heart disease (aortic or mitral)
Side effects
Common or very common Agitation; appetite decreased; asthenia; ataxia; behaviour abnormal; constipation; diarrhoea; drowsiness; fall; fever; hypersalivation; increased risk of infection; insomnia; mood altered; muscle tone decreased; status epilepticus; tremor; vomiting; weight decreased Frequency not known Angle closure glaucoma; mydriasis; pulmonary arterial hypertension; suicidal behaviours
Interactions
**Other interactions (2):**
- Patients being treated with a monoamine oxidase inhibitor should not receive indirectly-acting sympathomimetic agents such as amphetamines, metaraminol, fenfluramine or similar anorectic agents,...
- Potentiation of the blood-glucose-lowering effect and, thus, in some instances hypoglycaemia may occur when one of the following medicinal products is taken, for example: - phenylbutazone,...
Pregnancy
Important safety information For fenfluramine MHRA/CHM advice: Antiepileptics: risk of suicidal thoughts and behaviour (August 2008) See Epilepsy . MHRA/CHM advice: Antiepileptic drugs: updated advice on switching between different manufacturers' products (November 2017) See Epilepsy . MHRA/CHM advice: Antiepileptic drugs in pregnancy: updated advice following comprehensive safety review (January 2021) See Epilepsy .
Breast feeding
Avoid-present in milk in animal studies. M
Hepatic impairment
When used for Adjunctive therapy of seizures associated with Dravet syndrome [without concomitant stiripentol] or Adjunctive therapy of seizures associated with Lennox-Gastaut syndrome: Caution. M When used for Adjunctive therapy of seizures associated with Dravet syndrome [with concomitant stiripentol]: Avoid in moderate to severe impairment (no information available). M Dose adjustments When used for Adjunctive therapy of seizures associated with Dravet syndrome [without concomitant stiripentol] or Adjunctive therapy of seizures associated with Lennox-Gastaut syndrome: Consider slower dose titration in all degrees of impairment. Maximum dose 0.2 mg/kg twice daily (maximum 17 mg per day) in severe impairment. M When used for Adjunctive therapy of seizures associated with Dravet syndrome [with concomitant stiripentol]: Consider slower dose titration in mild impairment. M
Renal impairment
When used for Adjunctive therapy of seizures associated with Dravet syndrome [without concomitant stiripentol] or Adjunctive therapy of seizures associated with Lennox-Gastaut syndrome: Caution. M When used for Adjunctive therapy of seizures associated with Dravet syndrome [with concomitant stiripentol]: Avoid (no information available). M Dose adjustments When used for Adjunctive therapy of seizures associated with Dravet syndrome [without concomitant stiripentol] or Adjunctive therapy of seizures associated with Lennox-Gastaut syndrome: Consider slower dose titration. M
Medicinal forms
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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