Fenfluramine

How it works

It acts mainly through serotonergic activity, increasing serotonin release and activating serotonin receptors, with additional sigma-1 receptor modulation contributing to its anticonvulsant effect.

Prescribing in practice

• Because of the risk of valvular heart disease and pulmonary arterial hypertension, cardiac assessment with echocardiography is required before and during treatment under a controlled access programme.
• Decreased appetite and weight loss are common, so growth and weight must be monitored, especially in children.
• Avoid concomitant use with other serotonergic agents because of the risk of serotonin syndrome, and withdraw gradually rather than stopping abruptly.

Monitoring

Echocardiography is performed before starting and at regular intervals to detect valvulopathy or pulmonary hypertension, alongside monitoring of weight, growth and seizure frequency.

Counselling the patient

• Your child will need regular heart scans while taking this medicine.
• Tell us about reduced appetite, breathlessness or tiredness, and attend all monitoring appointments.
• Do not stop the medicine suddenly without medical advice.

Evidence & guidelines

Randomised controlled trials demonstrated substantial reductions in convulsive seizure frequency in Dravet syndrome, and the MHRA has highlighted the requirement for cardiac monitoring.