Side effects may include flushing, upper abdominal pain, nausea, vomiting, and diarrhea. These tend to occur in the early stages of treatment with this drug, but lessen with ongoing treatment. Other side effects may include low white blood cells and high liver enzymes.
Serious side effects of dimethyl fumarate include anaphylaxis and angioedema, with difficulty breathing, hives, and swelling of the throat and tongue. PML (progressive multifocal leukoencephalopathy), a serious viral brain infection, has occurred in a person taking dimethyl fumarate. People taking dimethyl fumarate who receive a live vaccine may develop serious infections.
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