Aminosalicylates are available in four different varieties:

Aminosalicylates are also available in various formulations. The type of formulation used will depend upon the location of inflammation in the digestive tract.

Mesalalmine preparations such as Asacol and Pentasa are modified to release the medication to specific locations with in the gastrointestinal tract. Asacol is a delayed release formulation which generally releases mesalamine only in the colon. Therefore it is only useful in patients with colitis, and not those with disease involving the small bowel. Pentasa, on the other hand, is a prolonged release formulation, which delivers mesalamine throughout the colon, from the duodenum to the rectum. The most common way to take aminosalicylates is via a conventional oral preparation of tablets or capsules.

Other methods of delivering these drugs include:

• Enemas. Used for left-sided colitis only. Mesalamine is the drug used for this purpose, and it is applied in the colon up to the splenic flexure, a bend that appears near the spleen. About 80 percent of patients who use these enemas once daily report beneficial effects, according to the Crohn's & Colitis Foundation of America (CCFA).
  
  
• Suppositories. These are solid medications that are inserted into a body cavity other than the mouth (e.g., rectum) before melting and passing into the bloodstream. They are used for ulcerative proctitis, a condition in which inflammation is limited to the rectum. Mesalamine is also used in this treatment and is applied from the rectum up to the sigmoid colon. The drug is usually administered twice daily, and the effectiveness of suppositories may be increased by combining this therapy with mesalamine pills.