Asacol (Mesalamine) is used to treat ulcerative colitis, proctitis, and proctosigmoiditis. It is also used to prevent the symptoms of ulcerative colitis from recurring. It works by affecting a substance in the body that causes inflammation, tissue damage, and diarrhea. Do not crush, break, or chew an Asacol  tablet. Swallow the pill whole. The extended-release capsule is specially formulated to release the medicine after it has passed through your stomach into your intestines. Breaking the pill may cause the drug to be released too early in the digestive tract. The enteric-coated tablet has a special coating to protect your stomach. Breaking the pill could damage this coating. Call your doctor if you find undissolved tablets in your stool. Store mesalamine at room temperature away from moisture and heat.