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You should tell your doctor and you should not take Asacol® HD if you are allergic to salicylates (including mesalamine, aspirin, or aspirin-containing products) or to any of the ingredients of Asacol® HD.

Reports of problems with kidney function have been associated with mesalamine-containing products like Asacol® HD. Tell your doctor if you have or have had any problems with your kidneys. It is recommended that all patients have their kidney function checked before starting Asacol® HD and periodically while on therapy.

Products that contain mesalamine, like Asacol® HD, have been associated with a condition that may be difficult to distinguish from an ulcerative colitis flare-up. Symptoms include cramping, stomach ache, bloody diarrhea, and sometimes fever, headache, and rash. If you experience any of these symptoms, talk to your doctor immediately. Your doctor may decide to discontinue your medication.

Tell your doctor if you are allergic to sulfasalazine, as you may also be allergic to Asacol® HD or drugs that contain or are converted to mesalamine. Some patients taking Asacol® HD or mesalamine-containing products have reported heart-related allergic reactions, such as inflammation of the heart muscle and inflammation of the lining of the heart. Tell your doctor if you have or have had a history of myocarditis or pericarditis as this may increase your likelihood of having these types of reactions.

Reports of liver failure have been associated with mesalamine-containing products like Asacol® HD in patients that have or have had liver disease. Tell your doctor if you have a problem with your liver.

Tell your doctor if you have a history of obstruction or a narrowing of the stomach passage leading into the small intestine, as this may delay the release of the medicine.

Asacol® HD has not been studied in pregnant women. Talk to your doctor if you are pregnant, planning to become pregnant, or are breastfeeding because Asacol® HD may not be right for you.

In clinical trials, common side effects reported with Asacol® HD included headache, runny nose, diarrhea, stomach pain, belching, flatulence, general pain, and upset stomach. Other side effects may occur.

You should not substitute one Asacol® HD 800 mg tablet for two Delzicol® (mesalamine) delayed-release 400 mg tablets.


Asacol® HD (mesalamine) delayed-release tablets are available only by prescription for the treatment of moderately active ulcerative colitis (UC) in adults.

Please see Full Prescribing Information for Asacol® HD.

To report a side effect from one of our products, please call the Allergan Drug Safety Department at 1‑800‑678‑1605.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit, or call 1‑800‑FDA‑1088.