Fumaric acid ester (immunomodulator) Pregnancy: A moderate amount of data in pregnant women (300–1,000 outcomes) with exposure in early pregnancy indicates no malformative or foeto/neonatal toxicity compared with the general population; the risk of longer exposure or exposure in later pregnancy is not known and animal studies have shown reproductive toxicity. As a precautionary measure it is preferable to avoid use during pregnancy, and dimethyl fumarate should be used during pregnancy only if clearly needed and if the potential benefit justifies the potential risk to the foetus. Breast-feeding: it is unknown whether dimethyl fumarate or its metabolites are excreted in human milk and a risk to the newborn/infant cannot be excluded — decide whether to discontinue breast-feeding or the therapy. No human fertility data.

Dimethyl fumarate

Brand names: Tecfidera, Skilarence (psoriasis)

Dimethyl fumarate is an oral disease-modifying therapy for relapsing-remitting multiple sclerosis.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Starting dose 120 mg twice a day; after 7 days the dose should be increased to the recommended maintenance dose of 240 mg twice a day

Route: Oral — gastro-resistant capsule swallowed whole; the capsule or its contents must not be crushed, divided, dissolved, sucked or chewed

Frequency: Twice daily, taken with food

Treatment should be initiated under supervision of a physician experienced in the treatment of multiple sclerosis. A temporary dose reduction to 120 mg twice a day may reduce the occurrence of flushing and gastrointestinal adverse reactions; the recommended maintenance dose of 240 mg twice a day should be resumed within 1 month. MISSED DOSE: a double dose should not be taken — the missed dose may be taken only if there are 4 hours between doses, otherwise wait until the next scheduled dose. Taking with food may improve tolerability in patients who experience flushing or gastrointestinal adverse reactions. MONITORING: a current complete blood count including lymphocytes must be performed before initiation and every 3 months thereafter; do not initiate in severe lymphopenia (lymphocyte count <0.5 x 10⁹/L); discontinue in prolonged severe lymphopenia persisting more than 6 months and re-assess the benefit/risk balance for sustained moderate reductions (≥0.5 to <0.8 x 10⁹/L) lasting more than 6 months. Assess renal function before initiation, after 3 and 6 months, every 6 to 12 months thereafter and as clinically indicated; assess serum aminotransferases and total bilirubin before initiation and during treatment as clinically indicated. A baseline MRI should be available before initiating treatment. ELDERLY: clinical studies had limited exposure in patients aged 55 years and above and insufficient numbers aged 65 and over; based on the mode of action there is no theoretical requirement for dose adjustment. PAEDIATRIC: the posology is the same in adults and in paediatric patients aged 13 years and older; there are limited data in children between 10 and 12 years old and no posology recommendation can be made for that group; safety and efficacy in children aged less than 10 years have not been established. Because the SPC states an adult-equivalent dose rather than a per-kg rule, no structured per-kg paediatric dose is recorded — verify paediatric dosing against a children's formulary. Source: eMC SPC for Dimethyl fumarate 120 mg Gastro-resistant capsule (§4.2).

Dose adjustments

Renal

Dimethyl fumarate has not been studied in patients with renal impairment; based on clinical pharmacology studies no dose adjustments are needed, but caution should be used when treating patients with severe renal impairment. Assessment of renal function is recommended prior to treatment initiation, after 3 and 6 months of treatment, every 6 to 12 months thereafter and as clinically indicated.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Suspected or confirmed progressive multifocal leukoencephalopathy (PML)

Side effects

Flushing (very common, 35%) and hot flush (common) — tend to begin early, primarily during the first month, and may continue intermittently throughout treatment
Gastrointestinal events — diarrhoea (14%), nausea (12%), abdominal pain (10%) and upper abdominal pain (10%) are very common; vomiting, dyspepsia, gastritis and gastrointestinal disorder are common
Lymphopenia and leucopenia (common); thrombocytopenia (uncommon)
Progressive multifocal leukoencephalopathy (PML) and herpes zoster (frequency not known); gastroenteritis (common)
Increased aspartate and alanine aminotransferase (common); drug-induced liver injury (rare)
Proteinuria (common); ketones measured in urine (very common); pruritus, rash, erythema and alopecia (common)

Clinical monograph

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.

Reference: NICE TA320; NICE TA475; ABN MS-DMT; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways