What are the side effects, particularly gastrointestinal (GI) side effects, of Mycophenolate (Mycophenolic acid) mofetil 2000mg/day for Bullous Pemphigoid?

From the FDA Drug Label

Mycophenolate mofetil can cause serious side effects: Low blood cell counts. Stomach problems. Stomach and intestinal bleeding can happen in people who take high doses of mycophenolate mofetil. Common side effects include:

• diarrhea.
• vomiting
• pain
• stomach area pain
• swelling of the lower legs, ankles and feet
• high blood pressure

The side effects of Mycophenolate mofetil 2000mg/day for Bullous Pemphigoid include:

• Low blood cell counts: decreased white blood cells, red blood cells, and platelets
• Gastrointestinal (GI) side effects:
  • Diarrhea
  • Vomiting
  • Stomach pain
  • Stomach and intestinal bleeding (can be severe and require hospitalization)
  • Gastrointestinal perforations (rare)
  • Ulceration and hemorrhage (infrequent)
• Other side effects:
  • High blood pressure
  • Swelling of the lower legs, ankles, and feet
  • Pain
  • Fever
  • Infection
  • Sepsis
  • Asthenia
  • Chest pain
  • Back pain
  • Ascites
  • Anemia
  • Leukopenia
  • Thrombocytopenia
  • Hypochromic anemia
  • Leukocytosis
  • Urinary tract infection
  • Kidney function abnormal
  • Hypertension
  • Hypotension
  • Cardiovascular disorder
  • Tachycardia
  • Peripheral edema
  • Hypercholesteremia
  • Edema
  • Hypokalemia
  • Hyperkalemia
  • Hyperglycemia
  • Creatinine increased
  • BUN increased
  • Lactic dehydrogenase increased
  • Hypomagnesemia
  • Hypocalcemia 1 1 1

From the Research

Mycophenolate mofetil (MMF) at 2000mg/day for bullous pemphigoid commonly causes gastrointestinal side effects, including diarrhea, nausea, vomiting, abdominal pain, and gastritis, in approximately 20-40% of patients, as reported in studies such as 2 and 3. The most frequent GI issues associated with MMF treatment are:

• Diarrhea
• Nausea
• Vomiting
• Abdominal pain
• Gastritis These symptoms typically occur within the first few weeks of treatment and may diminish over time as the body adjusts to the medication. More severe but less common GI complications can include:
• Gastrointestinal bleeding
• Perforation To minimize these side effects, patients should:
• Take MMF with food
• Split the daily dose (1000mg twice daily rather than 2000mg once daily)
• Ensure adequate hydration Starting at a lower dose (500mg twice daily) and gradually increasing to the target dose over 2-4 weeks may also improve tolerability, as suggested by the mechanism of action of MMF, which inhibits lymphocyte proliferation by blocking purine synthesis, but also affects rapidly dividing cells in the GI tract, leading to the digestive symptoms 4. If GI side effects become severe or persistent, dose reduction may be necessary, or the doctor might prescribe anti-nausea medications or antidiarrheal agents as adjunctive therapy. Regular monitoring of complete blood counts is also important as MMF can cause bone marrow suppression alongside the GI effects, as noted in studies such as 5 and 3. The exact mechanism of MMF-induced diarrhea is unknown, but it may be related to the drug's effect on the enzyme inosine monophosphate dehydrogenase (IMPDH), as hypothesized in 3. Overall, while MMF can be an effective treatment for bullous pemphigoid, its potential GI side effects must be carefully managed to minimize morbidity and mortality, and improve quality of life, as emphasized in studies such as 6.