(commonly known as Asacol®, Asasantine®, Mesasal)
5-ASA is one-half of the medication sulfasalazine. It is the 5-ASA portion (the "active" part), without the sulfa portion (the "carrier" part). Research carried out in the past 15 years has shown that many of the adverse reactions to sulfasalazine were, in fact, reactions to the inactive sulfa carrier portion and not to the active 5-ASA part. This led pharmaceutical companies to split the medication and manufacture just the 5-ASA part. In general, the 5-ASA group of medications has the effect of sulfasalazine without causing the same degree of side effects.
As with sulfasalazine, 5-ASA is used to treat mild-to-moderate flare-ups of inflammatory bowel disease (IBD). It decreases inflammation and reduces diarrhea and may also prevent flare-ups of IBD in some people. Those with proctitis (colitis limited to the rectum) or colitis involving the last meter of the colon may find that 5-ASA is more effective taken rectally, rather than orally. It may also delay the return of Crohn's disease after surgery.
5-ASA is generally used now instead of sulfasalazine, if neither one has been given before. It is the alternative treatment for people who can't take sulfasalazine because they can't tolerate its sulfa component. Like sulfasalazine, 5-ASA reduces the production of diarrhea-causing chemicals in the intestine. Also like sulfasalazine, it inactivates oxygen radicals that can destroy tissue.
Side effects are essentially the same as for sulfasalazine, but they occur far less often. When the medication is first taken, people may experience nausea, headaches, and diarrhea. Less common side effects include allergic reactions and abdominal pain.
5-ASA is available as tablets, capsules, enemas, and suppositories. The medication is the same, but the composition of each differs and targets specific sites in the small or large intestine. Tablets and capsules are useful for small bowel and upper colon IBD, enemas for the lower half of the colon IBD, and suppositories for rectal IBD (proctitis).