23.4
Drugs for Treatment of Ulcerative Colitis in IBD
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Q1: How does 5-ASA treat ulcerative colitis?
5-aminosalicylic acid (5-ASA) inhibits leukotriene and prostaglandin synthesis while scavenging free radicals and suppressing immune cell activities. It also blocks nuclear factor-κB, reducing proinflammatory cytokine production. These mechanisms work together to reduce mucosal inflammation in the colon.
Q2: What are azo prodrugs and how do they deliver 5-ASA to the colon?
Azo prodrugs like sulfasalazine and balsalazide bind active 5-ASA to an inert compound through an azo bond, while olsalazine contains 5-ASA as a dimer. These formulations resist small intestine absorption. When they reach the colon, colonic bacteria cleave the azo bond, releasing 5-ASA directly in affected areas.
Q3: How do coated mesalamine formulations target drug delivery to the colon?
Coated mesalamine formulations enclose 5-ASA molecules within a pH-sensitive enteric coat or semipermeable ethylcellulose film. This coating limits gastrointestinal absorption at the proximal end, ensuring increased drug delivery specifically to the colon where inflammation occurs.
Q4: What are the common side effects of 5-ASA therapy?
Common side effects include headache, nausea, and fatigue. Rare but serious adverse effects include hemolytic anemia and hepatitis with azo prodrugs, and interstitial nephritis with mesalamine. Mesalamine may also cause dyspepsia and skin rash.
Q5: Why are different 5-ASA formulations necessary for treating ulcerative colitis?
5-ASA is highly absorbed in the small intestine, limiting its effectiveness in the colon. Different formulations—azo prodrugs, dimers, and coated mesalamine—are designed to protect 5-ASA during small intestine transit and release it specifically in the colon where inflammation occurs.
Q6: Can aminosalicylates treat conditions beyond ulcerative colitis?
Yes, aminosalicylates show clinical efficacy in treating mild to moderate Crohn's disease involving the colon or distal ileum. They are effective in both inducing and maintaining remission across inflammatory bowel disease conditions, though they are first-line agents specifically for ulcerative colitis.
Q7: What additional side effects does sulfasalazine have compared to other aminosalicylates?
Beyond common aminosalicylate side effects, sulfasalazine causes skin reactions, leukopenia, and a reversible decrease in sperm count. These additional effects make monitoring important during sulfasalazine therapy, though many are reversible upon discontinuation.