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Colazal Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 12/1/2015

Colazal (balsalazide) is an anti-inflammatory drug used to treat active ulcerative colitis. Colazal is available in generic form. Common side effects of Colazal include headache, nausea, vomiting, joint pain, abdominal or stomach pain, diarrhea, trouble sleeping (insomnia), loss of appetite, runny nose, or cold symptoms.

For treatment of active ulcerative colitis in adult patients, the usual dose of Colazal is three 750 mg capsules to be taken 3 times a day for up to 8 weeks. The usual dose for pediatric patients aged 5 to 17 years dose is EITHER: three 750 mg capsules 3 times a day for up to 8 weeks; OR one 750 mg capsule 3 times a day for up to 8 weeks. Colazal may interact with antibiotics. Other drugs may interact with Colazal. Tell your doctor all prescription and over-the-counter medications and supplements you use. During pregnancy, Colazal should be used only when prescribed. It is not known if this medication passes into breast milk. Consult your doctor before breast-feeding.

Our Colazal (balsalazide) 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.

What is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Colazal in Detail - Patient Information: Side Effects

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

Stop using balsalazide and call your doctor at once if you have any of these serious side effects:

  • worsening colitis symptoms, such as fever, stomach pain, cramps, or bloody diarrhea;
  • bleeding from your rectum; or
  • pale skin, easy bruising, weakness.

Less serious side effects may include:

  • headache, sleep problems (insomnia);
  • nausea, vomiting, stomach pain, diarrhea;
  • runny nose, cold symptoms; or
  • joint pain.

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.

Read the entire detailed patient monograph for Colazal (Balsalazide)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Colazal Overview - Patient Information: Side Effects

SIDE EFFECTS: Headache, nausea, vomiting, joint pain, diarrhea, abdominal pain, fever, sore throat, trouble sleeping, or loss of appetite may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Infrequently, balsalazide can worsen ulcerative colitis. Tell your doctor immediately if your symptoms worsen after starting this medication (e.g., increased abdominal pain, rectal bleeding).

Tell your doctor immediately if any of these rare but very serious side effects occur: change in the amount of urine, yellowing eyes/skin, dark urine, unusual/extreme tiredness, severe stomach/abdominal pain, persistent nausea/vomiting, burning/painful urination, fast/pounding heartbeat.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Colazal (Balsalazide)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Colazal FDA Prescribing Information: Side Effects
(Adverse Reactions)


Clinical Studies Experience

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

Adult Ulcerative Colitis

During clinical development, 259 adult patients with active ulcerative colitis were exposed to 6.75 g/day COLAZAL in 4 controlled trials.

In the 4 controlled clinical trials patients receiving a COLAZAL dose of 6.75 g/day most frequently reported the following adverse reactions: headache (8%), abdominal pain (6%), diarrhea (5%), nausea (5%), vomiting (4%), respiratory infection (4%), and arthralgia (4%). Withdrawal from therapy due to adverse reactions was comparable among patients on COLAZAL and placebo.

Adverse reactions reported by 1% or more of patients who participated in the 4 well-controlled, Phase 3 trials are presented by treatment group (Table 1).

The number of placebo patients (35), however, is too small for valid comparisons. Some adverse reactions, such as abdominal pain, fatigue, and nausea were reported more frequently in women than in men. Abdominal pain, rectal bleeding, and anemia can be part of the clinical presentation of ulcerative colitis.

Table 1: Adverse Reactions Occurring in ≥ 1% of Adult COLAZAL Patients in Controlled Trials*

Adverse Reaction COLAZAL 6.75 g/day
Abdominal pain 16 (6%) 1 (3%)
Diarrhea 14 (5%) 1 (3%)
Arthralgia 9 (4%) 0%
Rhinitis 6 (2%) 0%
Insomnia 6 (2%) 0%
Fatigue 6 (2%) 0%
Flatulence 5 (2%) 0%
Fever 5 (2%) 0%
Dyspepsia 5 (2%) 0%
Pharyngitis 4 (2%) 0%
Coughing 4 (2%) 0%
Anorexia 4 (2%) 0%
Urinary tract infection 3 (1%) 0%
Myalgia 3 (1%) 0%
Flu-like disorder 3 (1%) 0%
Dry mouth 3 (1%) 0%
Cramps 3 (1%) 0%
Constipation 3 (1%) 0%
*Adverse reactions occurring in at least 1% of Colazal patients which were less frequent than placebo for the same event were not included in the table.

Pediatric Ulcerative Colitis

In a clinical trial in 68 pediatric patients aged 5 to 17 years with mildly to moderately active ulcerative colitis who received 6.75 g/day or 2.25 g/day COLAZAL for 8 weeks, the most frequently reported adverse reactions were headache (15%), abdominal pain upper (13%), abdominal pain (12%), vomiting (10%), diarrhea (9%), colitis ulcerative (6%), nasopharyngitis (6%), and pyrexia (6%). [see Table 2]

One patient who received COLAZAL 6.75 g/day and 3 patients who received COLAZAL 2.25 g/ day discontinued treatment because of adverse reactions. In addition, 2 patients in each dose group discontinued because of a lack of efficacy.

Adverse reactions reported by 3% or more of pediatric patients within either treatment group in the Phase 3 trial are presented in Table 2.

Table 2: Treatment-Emergent Adverse Reactions Reported by ≥ 3% of Patients in Either Treatment Group in a Controlled Study of 68 Pediatric Patients

Adverse Reaction COLAZAL 6.75 g/day
2.25 g/day
Headache 5 (15%) 5 (14%) 10 (15%)
Abdominal pain upper 3 (9%) 6 (17%) 9 (13%)
Abdominal pain 4 (12%) 4 (11%) 8 (12%)
Vomiting 1 (3%) 6 (17%) 7 (10%)
Diarrhea 2 (6%) 4 (11%) 6 (9%)
Colitis ulcerative 2 (6%) 2 (6%) 4 (6%)
Nasopharyngitis 3 (9%) 1 (3%) 4 (6%)
Pyrexia 0 (0%) 4 (11%) 4 (6%)
Hematochezia 0 (0%) 3 (9%) 3 (4%)
Nausea 0 (0%) 3 (9%) 3 (4%)
Influenza 1 (3%) 2 (6%) 3 (4%)
Fatigue 2 (6%) 1 (3%) 3 (4%)
Stomatitis 0 (0%) 2 (6%) 2 (3%)
Cough 0 (0%) 2 (6%) 2 (3%)
Pharyngolaryngeal pain 2 (6%) 0 (0%) 2 (3%)
Dysmenorrhea 2 (6%) 0 (0%) 2 (3%)

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of balsalazide in clinical practice:

myocarditis, pericarditis, vasculitis, pruritus, pleural effusion, pneumonia (with and without eosinophilia), alveolitis, renal failure, interstitial nephritis, pancreatitis, and alopecia.

Because these reactions are reported voluntarily from a population of unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. These adverse reactions have been chosen for inclusion due to a combination of seriousness, frequency of reporting, or potential causal connection to balsalazide.


Postmarketing adverse reactions of hepatotoxicity have been reported for products which contain (or are metabolized to) mesalamine, including elevated liver function tests (SGOT/AST, SGPT/ALT, GGT, LDH, alkaline phosphatase, bilirubin), jaundice, cholestatic jaundice, cirrhosis, hepatocellular damage including liver necrosis and liver failure. Some of these cases were fatal; however, no fatalities associated with these adverse reactions were reported in COLAZAL clinical trials. One case of Kawasaki-like syndrome which included hepatic function changes was also reported, however, this adverse reaction was not reported in COLAZAL clinical trials.

Read the entire FDA prescribing information for Colazal (Balsalazide)

Colazal - User Reviews

Colazal User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Colazal sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


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

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