Gastroenterology: Medications

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All About Asacol ( mesalamine )

Many patients are not as well-informed about prescription medications as they ought to be. We believe that the more you know about your medications, the better. Therefore, we have written this to explain more about Asacol and to explain the importance of taking it properly.

If any of this information causes you concern or if you want additional information about your medicine and its use, please check with your doctor or pharmacist.

Remember to keep all prescription drugs beyond the sight and reach of children when not in use. Store all drugs in their original labeled containers; the place of storage should be cool, dry, and away from light. Always read the label before each use.

What is Asacol?

Approved by the FDA in 1997, Asacol (Aze-a-call) is a man-made compound that is taken by mouth to treat inflammatory disorders of the colon such as ulcerative colitis, Crohn's colitis, and other inflammatory conditions. It is sometimes given in conjunction with other medications such as the steroid, prednisone. It is also used in cases of Crohn's disease which only involve the end of the small intestine, called the terminal (meaning "end of") ileum.

Asacol is the better half of Azulfidine

The active ingredient in Asacol, mesalamine (5-aminosalicylic acid, also referred to as 5-ASA), is the major active component of Azulfidine (sulfasalazine) which has been used for over 50 years in the treatment of inflammatory bowel disease. It turns out that some patients have an adverse reaction to Azulfidine, mostly due to its similarity to sulfa compounds. Scientists were able to remove the sulfa-like portion of Azulfidine, while maintaining the full beneficial effect. The result was meslamine, an aspirin-like antiinflammatory drug, named Asacol. Each brown-red capsule-shaped enteric coated tablet of Asacol contains 400 mg of mesalamine.

Targeted Delivery

One of the unique features of Asacol is the fact that the pill does not release its medication until it reaches the diseased area. Each tablet has a special plastic coating which delays release of mesalamine until the tablets reach the end of the 20 feet of small intestine, or the ileum. This allows delivery of most of the medicine right where the problem lies - the ileum and the colon. How mesalamine works is unknown, but it appears to be topical rather than systemic. Once released in the colon, mesalamine is minimally absorbed. Most of it works directly on the lining of the ileum and colon - like putting a salve on a rash. Eventually most of it is excreted with the stool.

Studies have shown that Asacol can help bring a case of colitis under control and help maintain a remission over time. Realize that colitis rarely goes into permanent remission, but the risk of flare-ups can be substantially reduced by continued use of Asacol at the maintenance dose as directed by your doctor.

What Asacol is not.

Asacol is not a steroid like prednisone. It is not habit forming; it does not cause drowsiness. Since it lacks the sulfa-like properties of Azulfidine, most patients intolerant or allergic to Azulfidine and other sulfa drugs can be safely treated with Asacol. In addition, Asacol does not reduce a man's sperm count as does Azulfidine. There are no known interactions with other medications. As yet, there is no generic substitution available.

Taking Asacol properly

1. Swallow Asacol tablets whole, taking care not to break the outer coating. It is important that you do not break or crush them. The outer coating is designed to remain intact, to protect the active ingredient until it reaches the end of the 20 feet of the small intestine, where the tablet coating dissolves and the contents of the tablet are released directly into the ileum and colon. You can take Asacol with or without food. Most patients take half their daily dose with breakfast and half with supper.

2. Take the dose as prescribed. There is no fixed rule for the correct dose of Asacol. Each case is different. The usual daily adult dose is 2 to 8 Asacol 400 mg tablets per day, taken orally in divided doses. In patients with severe active disease, the dose may be increased to 12 tablets daily. Initially, your doctor will determine what dose is best for you on the basis of your age, weight, the activity of your disease, and any other medical conditions that you may have. Do not alter the prescribed dosage on your own. Your doctor will routinely reassess the optimal dose for you.

3. Do not skip doses. There is no harm in an occasional missed dose. If you do miss a dose, simply skip the missed dose and then go back to your regular dosing schedule. Do not intentionally double doses.

4. Do not stop taking this medication on your own. Typically, Asacol is prescribed for long-term treatment of inflammatory bowel disease. Not only does Asacol help reduce the symptoms of an acute attack, but it also helps to reduce the risk of future attacks. Stopping this medication may trigger another flare up of intestinal inflammation and make you ill. Only stop Asacol under your doctor's supervision.

5. What appears to be intact or partially intact tablets may occasionaly show up in the stool, particularly during times of severe diarrhea. If this occurs repeatedly, consult your physician.

What are the side effects?

All medicines - even those purchased without a prescription - may sometimes produce unwanted side effects. Over 5 million prescription have been written in the United States and Canada and Asacol has been generally well tolerated. Adverse events seen in clinical trials with Asacol tablets have generally been mild and reversible, and have seldom resulted in discontinuation of treatment. Asymptomatic minor elevations of liver function tests have occurred in patients taking Asacol tablets. These elevations usually resolve during continued therapy.

These side effects should be reported to your doctor:

  • Persistent headaches
  • Skin rash, severe itching
  • Unexplained fever
  • Unusual bleeding or bruising
  • Unexplained skin blistering and peeling
The following side effects usually do not require medical attention. They often will go away as your body becomes used to the medication. However, if they continue or are bothersome, check with your doctor:
  • Mild Headache
  • Upset stomach, heartburn
  • Nausea and vomiting
  • Dizziness
Some patients may experience side effects not listed above. If you notice any other symptoms, simply consult your doctor, nurse, or pharmacist.

Limiting side effects

You can help limit side effects by taking Asacol exactly as prescribed and by reporting any problems promptly to your doctor. Drink plenty of fluids.


Do not take Asacol if you are allergic to aspirin or have untreated peptic ulcer disease. Inform your doctor if you are pregnant, planning to become pregnant soon, or breast-feeding. Although there is no evidence that Asacol is dangerous during pregnancy, we feel it is best to avoid all potent prescription drugs at these times whenever possible.


Asacol is a powerful drug that can be of tremendous benefit to you. As with all medications, however, side effects may occur. You can best limit problems with this medication by taking it exactly as prescribed. If you have any questions or concerns, please do not hesitate to discuss them with your doctor.

For more information about Asacol, access the Asacol Website.

Text & Images Courtesy of Three Rivers Endoscopy Center
© Dr. Robert Fusco, Three Rivers Endoscopy Center, All Rights Reserved

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