Fenfluramine is recommended as an option for treating seizures associated with Lennox–Gastaut syndrome (LGS), as an add-on to other antiseizure medicines, for people 2 years and over. It is recommended only if:
the frequency of drop seizures is checked every 6 months, and fenfluramine is stopped if the frequency is not reduced by at least 30% compared with the 6 months before starting treatment
the company provides it according to the commercial arrangement.
This recommendation is not intended to affect treatment with fenfluramine that was started in the NHS before this guidance was published. People having treatment outside this recommendation may continue without change to the funding arrangements in place for them before this guidance was published, until they and their NHS healthcare professional consider it appropriate to stop. For children or young people, this decision should be made jointly by the healthcare professional, the child or young person, and their parents or carers.
Why the committee made these recommendations
People with LGS are offered a range of antiseizure medicines. If this does not control their seizures, other treatments can be introduced, including cannabidiol plus clobazam. People with LGS would have fenfluramine if their drop seizures are not controlled well enough after trying 2 or more antiepileptic drugs. For this appraisal, a rule was included for stopping fenfluramine if it has not lowered the drop seizure frequency enough. This is not in the licence for fenfluramine, but matches how cannabidiol plus clobazam is used in the NHS.
Evidence from a clinical trial shows that people who have fenfluramine have fewer drop seizures per month than people who have standard care without cannabidiol plus clobazam. There is no evidence directly comparing fenfluramine with cannabidiol plus clobazam and the results of an indirect comparison are uncertain. So, it is unclear whether fenfluramine or cannabidiol plus clobazam works better at reducing the number of drop seizures.
Because of uncertainties in the clinical-effectiveness evidence and the economic model, the cost-effectiveness estimates are uncertain. But a cost comparison suggests that fenfluramine has similar or lower costs to cannabidiol plus clobazam. So, fenfluramine is recommended.