Dimethyl fumarate

How it works

It and its active metabolite activate the Nrf2 antioxidant pathway and modulate immune cell responses, producing anti-inflammatory and cytoprotective effects, though the precise mechanism in MS is not fully defined.

Prescribing in practice

• Prolonged lymphopenia increases the risk of progressive multifocal leukoencephalopathy, so full blood count must be monitored and treatment reviewed or withdrawn if severe sustained lymphopenia develops.
• Flushing and gastrointestinal upset are common early and may be eased by taking with food and, where appropriate, short-term symptomatic measures.
• Check full blood count and liver and renal function before starting, and counsel patients to report symptoms of serious infection.

Monitoring

Monitor full blood count (especially lymphocytes) before and regularly during treatment, alongside liver and renal function, and remain alert for new neurological symptoms suggesting PML.

Counselling the patient

• Flushing and stomach upset are common at first and often settle; taking with food can help.
• Report persistent or worsening new neurological symptoms or signs of infection.
• Attend regular blood tests as scheduled.

Evidence & guidelines

The DEFINE and CONFIRM trials showed dimethyl fumarate reduces relapse rate and MRI activity in relapsing-remitting multiple sclerosis, supporting its NICE-recommended use.