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A to Z of MS Dimethyl fumarate (Tecfidera, BG-12)

Dimethyl fumarate is a disease modifying drug for relapsing remitting MS.

Dimethyl fumarate was approved for use on the NHS in 2014. The drug can be prescribed for adults with active relapsing remitting MS (generally defined as having two relapses which have had a substantial effect on health or daily life in the last two years), providing they do not have highly active or rapidly evolving severe relapsing remitting multiple sclerosis.

Studies have shown that dimethyl fumarate reduces the number of relapses by around one half and slows down progression.

Product names

Tecfidera, BG-12

How is dimethyl fumarate taken?

Dimethyl fumarate is taken as a capsule, twice daily.

Side effects and contraindications

The most common side effects include:

  • flushing and feeling hot
  • gastrointestinal upset - diarrhoea, nausea, abdominal pain
  • headache

How dimethyl fumarate works

In multiple sclerosis, the immune system mistakenly attacks the myelin sheath that surrounds nerve cells in the brain and spinal cord. The damage disrupts the way in which messages, or nerve impulses, are carried to and from the brain, leading to a variety of symptoms.

Dimethyl fumarate's mechanism of action is not fully understood, but laboratory studies suggest that it may work in two ways:

  • reduces the inflammation caused when the immune system attacks myelin, resulting in less damage to myelin
  • protects nerve cells from damage caused by chemicals released during the immune attack

Dimethyl fumarate research

Two main studies have provided the evidence to support approval of dimethyl fumarate for multiple sclerosis. Both studies found dimethyl fumarate effective at reducing the number of relapses to approximately half of that seen in those taking placebo (dummy pill). In one study (DEFINE) the progression of disability was reduced for people taking dimethyl fumarate; this effect was not seen in the second study (COMFIRM).

  • DEFINE - dimethyl fumarate compared to placebo

    This two year study compared dimethyl fumarate taken either two or three times daily and placebo in more than 1,200 participants with relapsing remitting MS. Compared to placebo, the drug reduced the number of relapses in one year by 53% for the twice daily dosing and 48% for the three times a day dosing.

    Dimethyl fumarate twice daily reduced the risk of disability progression by 38% while dimethyl fumarate three times per day reduced this risk by 34%.

  • CONFIRM - dimethyl fumarate or glatiramer acetate compared to placebo

    This two year study with 1,232 participants was similar to DEFINE, but with an additional group who took glatiramer acetate (Copaxone) for comparison.

    Dimethyl fumarate reduced the number of relapses in one year by 44% for the twice-daily dose and by 51% for the three times daily dose, compared to placebo. In contrast, glatiramer acetate reduced the number of relapses by 29% compared to placebo.

    The reduction in disability progression observed in the DEFINE study was not seen in the CONFIRM study.


National Institute for Health and Care Excellence (NICE).
dimethyl fumarate for treating relapsing-remitting multiple sclerosis.
NICE technology appraisal guidance 320.
Available from NICE website

Scottish Medicines Consortium (SMC).
Advice: dimethyl fumarate (Tecfidera) - 7 April 2014.
Available from SMC website

Gold R, et al.
Placebo-controlled phase 3 study of oral BG-12 for relapsing multiple sclerosis.
New England Journal of Medicine 2012;367:1098-107.

Fox RJ, et al.
Placebo-controlled phase 3 study of oral BG-12 or glatiramer in multiple sclerosis.
New England Journal of Medicine 2012;367:1087-97.

Patient Information Leaflet

Tecfidera (EMC website)
Webcast on drug therapy
Neurologist Prof David Bates addresses some of the questions people ask about disease modifying drugs
Watch the webcast

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