Although Tecfidera can cause stomach problems, it is unlikely to cause permanent stomach damage. Research has shown that up to 88% of people experience some stomach-related side effects, typically within the first three weeks of starting Tecfidera. Most stomach-related side effects are mild to moderate, with some people experiencing more than one type of event.

Common events include:

• Upper abdominal pain: experienced by 71%; 34% required treatment
• Flatulence: experienced by 66%; 31% required treatment
• Nausea: experienced by 65%; 30% required treatment
• Diarrhea: experienced by 64%; 28% required treatment
• Bloating: experienced by 60%; 30% required treatment
• Lower abdominal pain: experienced by 51%; 25% required treatment
• Indigestion: experienced by 37%; 19% required treatment
• Constipation: experienced by 33%; 17% required treatment
• Vomiting: experienced by 14%; 11% required treatment.

The incidence of serious gastrointestinal side effects was 1% in patients treated with Tecfidera. Only 6.6% of patients discontinued Tecfidera because of gastrointestinal (stomach-related) side effects. The severity of gastrointestinal side effects decreased with time.

Symptomatic treatment includes:

• Acid secretion blockers, such as proton pump inhibitors or H2 blockers
• Antidiarrheals
• Antiemetics.