This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Medicine
Drug of choice for acute exacerbation of ulcerative colitis is ? 
Select and explain. 
A. Sulfasalazine, B. Mesalazine, C. Steroids, D. NSAID's
B: Mesalazine
Answer: B: Mesalazine 
Explanation: <p>Davidson&;s principles and practice of medicine 22nd edition. Mesalamine (Asacol, Pentasa, Lialda, Rowasa, Canasa) Mesalamine is the drug of choice for maintaining remission. It is useful for the treatment of mild-to-moderateulcerative colitis. It is better tolerated and has less adverse effects than sulfasalazine. *Patients who fail to respon to maximum oral therapy and those who present with acute severe colitis should be given intravenous coico steroids. Topical and oral aminosalycilates have no role in acute attacks</p>