Asacol Side Effects Center

Last updated on RxList: 11/12/2021
Asacol Side Effects Center

What Is Asacol?

Asacol (mesalamine) is an anti-inflammatory drug used to treat ulcerative colitis, proctitis, and proctosigmoiditis, and is also used to prevent the symptoms of ulcerative colitis from recurring.

What Are Side Effects of Asacol?

Common side effects of Asacol include:

  • mild nausea,
  • vomiting,
  • stomach cramps,
  • diarrhea,
  • gas,
  • fever,
  • sore throat,
  • flu-like symptoms,
  • constipation,
  • headache,
  • dizziness,
  • tired feeling, or
  • skin rash.

Tell your doctor if you have serious side effects of Asacol including:

  • severe stomach pain,
  • cramping,
  • fever,
  • headache, and
  • bloody diarrhea.

Dosage for Asacol?

For the treatment of mildly to moderately active ulcerative colitis the usual adult dosage of Asacol is two 400-mg tablets to be taken three times a day for a total daily dose of 2.4 grams for a duration of 6 weeks. For the maintenance of remission of ulcerative colitis the recommended dosage in adults is 1.6 grams daily, in divided doses. Treatment duration is usually 6 months.

What Drugs, Substances, or Supplements Interact with Asacol?

Asacol may interact with azathioprine or mercaptopurine, pentamidine, tacrolimus, amphotericin B, antibiotics, antiviral medicines, cancer medicine, or aspirin or other NSAIDs (nonsteroidal anti-inflammatory drugs).

Asacol During Pregnancy and Breastfeeding

Tell your doctor all medications you use. Asacol is not expected to be harmful to a fetus. Tell your doctor if you are pregnant or plan to become pregnant during treatment. This medication can pass into breast milk and may harm a nursing baby. Consult your doctor before breastfeeding.

Additional Information

Our Asacol (mesalamine) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Asacol Consumer Information

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using mesalamine and call your doctor at once if you have:

  • severe stomach pain, stomach cramping, bloody diarrhea;
  • fever, headache, general ill feeling;
  • rash, itching, eye redness;
  • bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds;
  • low white blood cell counts--fever, chills, mouth sores, skin sores, sore throat, cough, feeling light-headed, trouble breathing;
  • signs of a kidney stone--severe pain in your side and back, frequent need to urinate, foul-smelling urine, dark or cloudy urine;
  • kidney problems--increased or decreased urination, swelling, weight gain; or
  • liver problems--loss of appetite, upper stomach pain, tiredness, easy bruising or bleeding, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Low white blood cell counts may be more likely in older adults.

Common side effects may include:

  • burping, constipation, nausea, vomiting, stomach pain, diarrhea, gas;
  • dizziness;
  • cold symptoms such as stuffy nose, sneezing, sore throat;
  • back pain;
  • headache;
  • rash; or
  • abnormal liver function tests.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Asacol Professional Information


The most serious adverse reactions seen in Asacol clinical trials or with other products that contain mesalamine or are metabolized to mesalamine are:

  • Renal impairment, including renal failure [see WARNINGS AND PRECAUTIONS]
  • Acute intolerance syndrome [see WARNINGS AND PRECAUTIONS]
  • Hypersensitivity reactions [see WARNINGS AND PRECAUTIONS]
  • Hepatic failure [see WARNINGS AND PRECAUTIONS]

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In total, Asacol tablets have been evaluated in 2,690 patients with ulcerative colitis in controlled and open-label trials. Adverse reactions presented in the following sections may occur regardless of length of therapy and similar reactions have been reported in short-and long-term studies and in the postmarketing setting.

Clinical studies supporting Asacol use for the treatment of mildly to moderately active ulcerative colitis included two 6-week, placebo-controlled, randomized, double-blind studies in adults with mildly to moderately active ulcerative colitis (Studies 1 and 2), and one 6-week, randomized, double-blind, study of 2 dose levels in children with mildly to moderately active ulcerative colitis. Clinical studies supporting the use of Asacol tablets in the maintenance of remission of ulcerative colitis included a 6-month, randomized, double-blind, placebo-controlled, multi-center study and four active-controlled maintenance trials comparing Asacol tablets with sulfasalazine. Asacol has been evaluated in 427 adults and 82 children with ulcerative colitis in these controlled studies.

Treatment of Mildly to Moderately Active Ulcerative Colitis in Adults

In two 6-week placebo-controlled clinical studies (Studies 1 and 2) involving 245 patients, 155 of whom were randomized to Asacol [see Clinical Studies], 3.2 percent of the Asacol-treated patients discontinued therapy because of adverse reactions as compared to 2.2 percent of the placebo-treated patients. The average age of patients in Study 1 was 42 years and 48 percent of patients were male. The average age of patients in Study 2 was 42 years and 59 percent of patients were male. Adverse reactions leading to withdrawal from Asacol included (each in one patient): diarrhea and colitis flare; dizziness, nausea, joint pain, and headache; rash, lethargy and constipation; dry mouth, malaise, lower back discomfort, mild disorientation, mild indigestion and cramping; headache, nausea, aching, vomiting, muscle cramps, a stuffy head, plugged ears, and fever.

Adverse reactions in patients treated with Asacol occurring at a frequency of at least 2 percent and at a rate greater than placebo in 6-week, double-blind, placebo-controlled trials (Studies 1 and 2) are listed in Table 2 below.

Table 2: Adverse Reactions Reported in Two Pooled Six-Week, Placebo-Controlled Trials (Studies 1 and 2) Experienced by at Least 2 percent of Patients in the Asacol Group and at a Rate Greater than Placebo

Adverse Reaction % of Patients with Adverse Reactions
(n = 152)
(n = 87)
Abdominal pain 18 14
Eructation 16 15
Pain 14 8
Back pain 7 5
Rash 6 3
Dyspepsia 6 1
Arthralgia 5 3
Vomiting 5 2
Constipation 5 1
Chest pain 3 2
Chills 3 2
Peripheral edema 3 2
Myalgia 3 1
Sweating 3 1
Pruritus 3 0
Acne 2 1
Malaise 2 1
Arthritis 2 0

Treatment of Mildly to Moderately Active Ulcerative Colitis in Pediatric Patients 5 to 17 Years Old

A randomized, double-blind, 6-week study of 2 dose levels of Asacol (Study 3) was conducted in 82 pediatric patients 5 to 17 years of age with mildly to moderately active ulcerative colitis. All patients were divided by body weight category (17 to less than 33 kg, 33 to less than 54 kg, and 54 to 90 kg) and randomly assigned to receive a low dose (1.2, 2.0, and 2.4 g/day for the respective body weight category) or a high dose (2.0, 3.6, and 4.8 g/day).

The high dose is not an approved dosage because it was not found to be more effective than the approved dose [see DOSAGE AND ADMINISTRATION and Clinical Studies].

Duration of exposure to mesalamine among the 82 patients in the study ranged from 12 to 50 days (mean of 40 days in each dose group). The majority (88 percent) of patients in each group were treated for more than 5 weeks. Table 3 provides a summary of the specific reported adverse reactions (ARs).

Table 3: Adverse Reactions Reported in One Six-Week Trial (Study 3) Experienced by at Least 5% of Patients in the Low Dose Group or High Dose Group

Adverse Reaction % of Patients with Adverse Reactions
Low Dose
High Dose
Nasopharyngitis 15 12
Ulcerative Colitis 12 5
Headache 10 5
Abdominal pain 10 2
Dizziness 7 2
Sinusitis 7 0
Rash 5 5
Cough 5 0
Diarrhea 5 0
Fatigue 2 10
Pyrexia 0 7
Increased Lipase 0 5
Low Dose = Asacol 1.2 – 2.4 g/day; High Dose = Asacol 2.0 – 4.8 g/day. Dosage was dependent on body weight. Adverse Reactions reported at the 1-week telephone follow-up visit are included.

Twelve percent of the patients in the low dose group and 5 percent of the patients in the high dose group had serious adverse reactions (ARs). Ulcerative colitis was reported as a serious AR in one subject in each group. Other serious ARs consisted of sinusitis, abdominal pain, decreased body mass index, adenovirus infection, bloody diarrhea, sclerosing cholangitis, and pancreatitis in one subject each in the low dose group and anemia and syncope in one subject each in the high dose group.

Seven patients were withdrawn from the study because of ARs: 5 (12 percent) in the low dose group (ulcerative colitis, adenovirus infection, sclerosing cholangitis, pancreatitis) and 2 (5 percent) in the high dose group (increased amylase and increased lipase, upper abdominal pain).

In general, the nature and severity of reactions in the pediatric population was similar to those reported in adult populations of patients with ulcerative colitis.

Maintenance of Remission of Ulcerative Colitis in Adults

In a 6-month placebo-controlled maintenance trial involving 264 patients (Study 4) 177 of whom were randomized to Asacol, six (3.4 percent) of the patients using Asacol discontinued therapy because of adverse reactions, as compared to four (4.6 percent) of patients using placebo [see Clinical Studies]. The average age of patients in Study 4 was 42 years and 55 percent of patients were male. Adverse reactions leading to study withdrawal in patients using Asacol included (each in one patient): anxiety; headache; pruritus; decreased libido; rheumatoid arthritis; and stomatitis and asthenia.

In addition to reactions listed in Table 2, the following adverse reactions occurred in patients using Asacol at a frequency of 2 percent or greater in Study 4: abdominal enlargement, gastroenteritis, gastrointestinal hemorrhage, infection, joint disorder, migraine, nervousness, paresthesia, rectal disorder, rectal hemorrhage, stool abnormalities, tenesmus, urinary frequency, vasodilation, and vision abnormalities.

In 3342 patients in uncontrolled clinical studies, the following adverse reactions occurred at a frequency of 5 percent or greater and appeared to increase in frequency with increasing dose: asthenia, fever, flu syndrome, pain, abdominal pain, back pain, flatulence, gastrointestinal bleeding, arthralgia, and rhinitis.

Postmarketing Experience

In addition to the adverse reactions reported above in clinical trials involving Asacol, the adverse reactions listed below have been identified during post-approval use of Asacol and other mesalaminecontaining products. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Body as a Whole: Neck pain, facial edema, edema, lupus-like syndrome, drug fever.

Cardiovascular: Pericarditis, myocarditis [see WARNINGS AND PRECAUTIONS].

Gastrointestinal: Anorexia, pancreatitis, gastritis, increased appetite, cholecystitis, dry mouth, oral ulcers, perforated peptic ulcer bloody diarrhea.

Hematologic: Agranulocytosis aplastic anemia, thrombocytopenia, eosinophilia, leukopenia, anemia, lymphadenopathy.

Musculoskeletal: Gout.

Nervous: Depression, somnolence, emotional lability, hyperesthesia, vertigo, confusion, tremor, peripheral neuropathy, transverse myelitis, Guillain-Barré syndrome.

Renal: Renal failure, interstitial nephritis, minimal change nephropathy [see WARNINGS AND PRECAUTIONS].

Respiratory/Pulmonary: Eosinophilic pneumonia, interstitial pneumonitis, asthma exacerbation, pleuritis.

Skin: Alopecia, psoriasis, pyoderma gangrenosus, dry skin, erythema nodosum, urticaria.

Special Senses: Eye pain, taste perversion, blurred vision, tinnitus.

Urogenital: Dysuria, urinary urgency, hematuria, epididymitis, menorrhagia, reversible oligospermia.

Laboratory Abnormalities: Elevated AST (SGOT) or ALT (SGPT), elevated alkaline phosphatase, elevated GGT, elevated LDH, elevated bilirubin, elevated serum creatinine and BUN.

Read the entire FDA prescribing information for Asacol (Mesalamine Delayed-Release Tablets)

© Asacol Patient Information is supplied by Cerner Multum, Inc. and Asacol Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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