A number of medications used to treat Crohn's disease and ulcerative colitis have as their active ingredient 5-aminosalicylic acid (5-ASA), an agent that inhibits substances in the immune system that cause inflammation. These include sulfasalazine (trade name Azulfadine), a compound that has been used for more than half a century.
Sulfasalazine is a so-called "sulfa drug." The sulfapyradine (an antibacterial organic sulfur compound) in sulfasalazine causes a number of side effects, which range from mild to severe headaches, nausea, and vomiting. These are usually dose-related, although some people cannot tolerate the medication at all. Azulfadine can be purchased in an enteric-coated tablet, which (for many people) reduces the incidence of nausea caused by uncoated tablets. For years, scientists sought ways to deliver 5-ASA without the sulfa-drug side effects.
During the 1990s, a number of new 5-ASA medications were approved. None are yet available as generics. They can be found under the following trade names and in the following formulations:
•Asacol (mesalamine), available as a 400-milligram coated caplet
•Pentasa (mesalamine), available as a 250-milligram capsule
•Rowasa (mesalamine), available as a 500-milligram rectal suppository or a 4,000 milligram enema (effective for Crohn's colitis, which affects the rectum and left side of the colon)
•Dipentum (osalazine), available as a 250-milligram capsule
Evidence shows that all of the new 5-ASA compounds are effective in large doses for treatment of flare-ups and in lower doses for maintenance therapy. Because these medications are expensive, many doctors prefer to try sulfasalazine first. The chemical structure of mesalamine is similar to aspirin; people with an allergy to aspirin should inform their doctors.
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