Ulcerative colitis is a chronic inflammatory condition primarily affecting the colon and rectum. The primary drugs used in the treatment of ulcerative colitis are aminosalicylates. They exhibit anti-inflammatory and immunosuppressive properties. They modulate inflammatory mediators and inhibit the activity of nuclear factor κB (NF-κB). Aminosalicylates also reduce inflammation by inhibiting prostaglandin and leukotriene production and decreasing neutrophil chemotaxis and superoxide generation.
Aminosalicylates have been designed to target specific gastrointestinal tract segments, ensuring effective delivery and absorption. Azo compounds such as sulfasalazine, balsalazide, and olsalazine contain 5-ASA bound by an azo bond to an inert compound or another 5-ASA molecule, allowing targeted drug delivery. At the same time, mesalamine is a unique formulation that packages 5-ASA itself in various ways to deliver it to different segments of the small or large bowel.
Clinically, aminosalicylates show efficacy in inducing and maintaining remission in ulcerative colitis. They also treat mild to moderate Crohn's disease involving the colon or distal ileum. Their potential adverse effects include hypersensitivity reactions, gastrointestinal disturbances, renal tubular damage, interstitial nephritis, and worsening of colitis. Sulfasalazine, a type of aminosalicylate, has additional side effects, including headache, skin reactions, leukopenia, and a reversible decrease in sperm count.
Ulcerative colitis is characterized by mucosal inflammation of the colon.
The first-line agent, 5-aminosalicylic acid or 5-ASA, inhibits leukotriene and prostaglandin synthesis, scavenges free radicals, and suppresses various immune cell activities. It may also block nuclear factor-κB, reducing proinflammatory cytokine production.
5-ASA is available in various formulations to counter its high small intestine absorption.
In azo prodrugs like sulfasalazine and balsalazide, active 5-ASA forms an azo bond with an inert compound, while in olsalazine, it exists as a dimer. Upon reaching the colon, the azo bond is cleaved by colonic bacteria, increasing 5-ASA levels in affected colon areas.
Common side effects include headache, nausea, fatigue, rarely hemolytic anemia, and hepatitis.
Coated mesalamine formulations, enclose 5-ASA molecules within a pH-sensitive enteric coat or semipermeable ethylcellulose film to limit GI absorption at the proximal end, ensuring increased drug delivery to the colon.
Mesalamine's adverse effects include headache, dyspepsia, skin rash, and rarely interstitial nephritis.
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