Which medication is an immunosuppressant used in Crohn's disease?

• A. Allopurinol
• B. Omeprazole
• C. Azathioprine
• D. 5-Fluorouracil

Answer: (C)

Immunosuppressants in Crohn's disease are used to dampen the immune response and help maintain remission, reducing the need for ongoing steroids. Azathioprine is a purine analog that inhibits DNA nucleotide synthesis, lowering the proliferation and activity of T and B lymphocytes. This mechanism makes it effective as a steroid-sparing maintenance therapy in Crohn's disease, often used after initial induction to sustain remission. Other choices don’t fit this role: allopurinol treats gout by inhibiting xanthine oxidase, omeprazole reduces stomach acid, and 5-fluorouracil is a chemotherapy agent with toxicity not used for Crohn's disease.