MS drug dimethyl fumarate possibly linked to serious GI adverse events

A Health Canada safety review has examined the potential risk of gastrointestinal events of perforation, ulceration, hemorrhage and obstruction with the use of oral dimethyl fumarate (Tecfidera, generics). The safety review was stimulated by a labelling update in the United States for all dimethyl fumarate-containing products.1Dimethyl fumarate 120 mg and 240 mg delayed-release capsules have been approved in Canada since 2013 for the treatment of adults with relapsing remitting multiple sclerosis (MS). The drug helps to reduce the number of relapses (flare-ups) and delays the progression of physical disability.1 Dimethyl fumarate is known to cause gastrointestinal adverse reactions (e.g., abdominal pain, diarrhea, nausea, vomiting, dyspepsia) and these side effects lead to discontinuation in about 4% of patients. Administration with food or temporary dose reduction is currently recommended for individuals with intolerance to gastrointestinal adverse reactions.2In their safety review, Health Canada examined 51 Canadian reports of gastrointestinal events of perforation, ulceration, hemorrhage or obstruction in patients taking dimethyl fumarate. However, due to incomplete information, reported events not meeting the definition of perforation, ulceration, hemorrhage or obstruction, or the presence of confounders (e.g., underlying medical conditions known to affect the gastrointestinal tract), these cases did not meet the criteria for further assessment.1 Health Canada also reviewed 22 international cases of gastrointestinal events of perforation, ulceration, hemorrhage or obstruction in patients taking dimethyl fumarate, including two cases from the published literature. Of the 22 cases, 18 cases (11 of hemorrhage unrelated to an ulcer, 4 cases of hemorrhage and ulcer, 2 cases of ulceration, 1 case of ulcer perforation) were found to be possibly linked to the use of dimethyl fumarate. One case of obstruction was unlikely to be linked, and three cases (2 of hemorrhage and 1 of ulcer perforation) were not assessable due to limited or conflicting clinical information. No deaths were reported.1In addition, Health Canada reviewed three published articles, which supported a link between the use of dimethyl fumarate and the risk of gastrointestinal events of perforation, ulceration, hemorrhage and obstruction.1In a recent article reviewing serious gastrointestinal adverse reactions for dimethyl fumarate that supported the post-market safety labelling change in the United States, researchers found that the majority of serious gastrointestinal reactions occurred early after drug initiation, with 50% of the events occurring within the first two months and 75% occurring within four months.2Overall, Health Canada concluded that there is a possible link between the use of dimethyl fumarate and the risk of gastrointestinal events of perforation, ulceration, hemorrhage and obstruction. Canadian product monographs for all dimethyl fumarate-containing products are being updated to include these risks.1Healthcare professionals are encouraged to report any side effects related to dimethyl fumarate to the Canada Vigilance Program (https://www.canada.ca/en/health-canada/services/drugs-health-products/medeffect-canada/canada-vigilance-program.html).1Health Canada plans to inform healthcare professionals about the risk of serious gastrointestinal events with dimethyl fumarate in a Health Product InfoWatch communication.1 Increased healthcare provider and patient awareness of the potential risks of serious gastrointestinal reactions with dimethyl fumarate may aid in early identification of these events and prompt initiation of treatment.2 References:Health Canada. Summary safety review - dimethyl fumarate - assessing the potential risk of gastrointestinal events of perforation, ulceration, hemorrhage and obstruction. January 7, 2026. (accessed January 7, 2026).Kim T, Brinker A, Croteau D, et al. Severe gastrointestinal adverse reactions including perforation, ulceration, hemorrhage, and obstruction: a fumaric acid ester class new safety risk. Mult Scler 2025;31(5):578-86. doi: 10.1177/13524585251316518.

MS drug dimethyl fumarate possibly linked to serious GI adverse events

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