Digestive Health Inflammatory Bowel Disease Treatment Side Effects of Asacol (Mesalamine) Other brands include Pentasa, Mesasal, and Salofalk By Amber J. Tresca facebook twitter linkedin Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16. Learn about our editorial process Amber J. Tresca Medically reviewed by Medically reviewed by Robert Burakoff, MD, MPH on July 21, 2020 linkedin Robert Burakoff, MD, MPH, is board-certified in gastroentrology. He is the vice chair for ambulatory services for the department of medicine at Weill Cornell Medical College in New York, where he is also a professor. He was the founding editor and co-editor in chief of Inflammatory Bowel Diseases. Learn about our Medical Review Board Robert Burakoff, MD, MPH Updated on September 17, 2020 Print Table of Contents View All Common Uncommon When to See a Doctor Warnings Asacol (mesalamine) is a 5-aminosalicylic acid (5-ASA) drug that was approved in August 1997 for the treatment of ulcerative colitis. Asacol acts topically on the intestines, suppressing the inflammation that is caused by ulcerative colitis—one of the main forms of inflammatory bowel disease (IBD). Asacol was previously also sometimes used to treat Crohn's disease, another type of IBD. However, it has since been studied more closely and IBD specialists now believe that mesalamine is not as effective for this purpose. As a result, it is no longer recommended for routine use in treating this form of IBD. Mesalamine can be effective when Crohn's disease involves the colon or large intestine, however. Asacol comes in various forms, including oral, suppositories, and liquid or foam enemas (rectal suspension). Because it acts topically, when the ulcerative colitis is affecting the last parts of the large intestine, the rectum, and the sigmoid colon, using a suppository or an enema may be helpful. Topical forms are not without the potential for side effects or adverse effects, so it's worth having an understanding of what those might entail. Pillbox Asacol Is a Maintenance Drug Asacol is classified as a "maintenance" drug, which means that it is given on a long-term basis to treat ulcerative colitis. Asacol can also be used as a first line treatment for acute mild ulcerative colitis. Ulcerative colitis causes inflammation in the colon, among other signs and symptoms throughout the body. Asacol is used to help stop the inflammation that is present in the colon and typically starts to take effect in about two to three weeks. After inflammation is under control, patients are prescribed this drug to help prevent more flare-ups of the disease from occurring. However, for adults with moderate to severe ulcerative colitis who have achieved remission on a biologic (e.g., Humira), small molecule (e.g., Xeljanz), or an immunomodulator medication, 2020 guidelines recommend against the use of Asacol for maintenance treatment. This maintenance drug is known to have a relatively low incidence of side effects, although some are still possible. The following is a list of the potential side effects and adverse effects of Asacol. Common Side Effects Check with your doctor if any of these side effects continue or are bothersome: Abdominal or stomach cramps or pain (mild)Diarrhea (mild)Dizziness; headache (mild)Runny or stuffy nose or sneezing Uncommon Side Effects Check with your doctor if any of these side effects continue or are bothersome: AcneBack or joint painGas or flatulenceIndigestionLoss of appetiteLoss of hair When to Seek Medical Attention These side effects are less common, but warrant an urgent call to your doctor: Abdominal or stomach cramps or pain (severe)Bloody diarrheaFeverHeadache (severe)Skin rash and itching Seek emergency medical care right away if you experience: AnxietyBack or stomach pain (severe)Blue or pale skinChest pain, possibly moving to the left arm, neck, or shoulderChillsFast heartbeatNausea or vomitingShortness of breathSwelling of the stomachUnusual tiredness or weaknessYellow eyes or skin Symptoms of an Overdose To avoid a greater risk of side effects and the possibility of an overdose, follow your prescriber's instructions. Symptoms of overdose, which warrant immediate medical attention, include: ConfusionDiarrhea (severe or continuing)Dizziness or lightheadednessDrowsiness (severe)Fast or deep breathingHeadache (severe or continuing)Hearing loss or ringing or buzzing in ears (continuing)Nausea or vomiting (continuing) Warnings Asacol is considered to be relatively safe, but people who take this drug should be aware that it has been associated with some adverse events. Some people have developed problems with their kidneys, and it's recommended that people taking this drug have their kidney function checked every so often. Some people have also had adverse reactions that mimic the symptoms of a flare-up of ulcerative colitis, which include diarrhea, headache, and abdominal pain. Allergic reactions are also possible. Your prescribing physician should be told about any previous allergic reactions to mesalamine or to sulfasalazine. A Word From Verywell Asacol is generally tolerated very well by most people, and it is often used long-term by those who have ulcerative colitis. However, as with any drug, there is the potential for adverse effects and side effects. For most people, the side effects are mild, but people taking Asacol should be aware of the potential for an allergic reaction, an adverse effect on the kidneys, or a worsening of diarrhea and abdominal pain. Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor. This information is meant only as a guideline. Always consult a physician or pharmacist for complete information about prescription medications. Was this page helpful? Thanks for your feedback! We're providing tips on how to take better care of your gut. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Feuerstein JD, Isaacs KL, Schneider Y, et al. AGA Clinical Practice Guidelines on the Management of Moderate to Severe Ulcerative Colitis. Gastroenterology. 2020. 158(5):1450-1461. doi:10.1053/j.gastro.2020.01.006 Additional Reading Actavis Pharma, Inc. ASACOL® HD (mesalamine) delayed-release tablets, for oral use Initial U.S. Approval: 1987. pi.actavis.com. Lichtenstein GR, Hanauer SB, Sandborn WJ; Practice Parameters Committee of American College of Gastroenterology. Management of Crohn's Disease in Adults. Am J Gastroenterol. 2009 Feb;104:465-483. doi:10.1038/ajg.2008.168