What is Colazal (balsalazide disodium)?

Colazal (balsalazide disodium) is an oral anti-inflammatory drug used to treat ulcerative colitis. It is a form of mesalamine (5-aminosalicyclic acid) that is activated by colonic bacteria when it reaches the colon. Ulcerative colitis and other inflammatory diseases cause excessive production of chemicals, for example, prostaglandins, that produce inflammation in the colon. 

Prostaglandins are produced by the enzymes, cyclooxygenase and lipoxygenase. These enzymes are overactive in individuals with ulcerative colitis. Mesalamine may work by blocking the activity of cyclooxygenase and lipoxygenase, thereby reducing the production of prostaglandins. Reduced production of prostaglandins decreases inflammation in the colon and symptoms associated with ulcerative colitis.

Common side effects of Colazal include:

Serious side effects of Colazal include:

There are no listed drug interactions of Colazal. Do not take Colazal if you have a hypersensitivity to salicylates such as aspirin

Animal studies have not demonstrated any adverse effects from Colazal on a fetus; however, there have been no studies in pregnant women. Colazal should only be used during pregnancy if the benefit outweighs the risks. 

It is unknown if Colazal is secreted into breast milk. Since many drugs are secreted into breast milk, Colazal is not recommended for use while breastfeeding.

What are the important side effects of Colazal (balsalazide disodium)?

Contact your doctor if:

  • You experience a worsening of your ulcerative colitis symptoms.
  • You are diagnosed with pyloric stenosis, because balsalazide disodium capsules may be slow to pass through your digestive tract.
  • You are diagnosed with renal dysfunction. Damage to the kidney has been observed in people given medications similar to balsalazide disodium.
  • You are diagnosed with liver disease. Worsening liver disease has been observed in some people given medications similar to balsalazide disodium.

In adult clinical trials the most common side effects were:

In the pediatric clinical trial the most common side effects were:

This is not a complete list of side effects. Discuss potential side effects with your doctor.

Colazal (balsalazide disodium) side effects list for healthcare professionals

Clinical Studies 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.

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 ReactionCOLAZAL 6.75 g/day
Abdominal pain16 (6%)1 (3%)
Diarrhea14 (5%)1 (3%)
Arthralgia9 (4%)0%
Rhinitis6 (2%)0%
Insomnia6 (2%)0%
Fatigue6 (2%)0%
Flatulence5 (2%)0%
Fever5 (2%)0%
Dyspepsia5 (2%)0%
Pharyngitis4 (2%)0%
Coughing4 (2%)0%
Anorexia4 (2%)0%
Urinary tract infection3 (1%)0%
Myalgia3 (1%)0%
Flu-like disorder3 (1%)0%
Dry mouth3 (1%)0%
Cramps3 (1%)0%
Constipation3 (1%)0%
*Adverse reactions occurring in at least 1% of COLAZAL patients which were less frequent than placebo for the same adverse reaction 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 ReactionCOLAZAL
6.75 g/day
2.25 g/day
Headache5 (15%)5 (14%)10 (15%)
Abdominal pain upper3 (9%)6 (17%)9 (13%)
Abdominal pain4 (12%)4 (11%)8 (12%)
Vomiting1 (3%)6 (17%)7 (10%)
Diarrhea2 (6%)4 (11%)6 (9%)
Colitis ulcerative2 (6%)2 (6%)4 (6%)
Nasopharyngitis3 (9%)1 (3%)4 (6%)
Pyrexia0 (0%)4 (11%)4 (6%)
Hematochezia0 (0%)3 (9%)3 (4%)
Nausea0 (0%)3 (9%)3 (4%)
Influenza1 (3%)2 (6%)3 (4%)
Fatigue2 (6%)1 (3%)3 (4%)
Stomatitis0 (0%)2 (6%)2 (3%)
Cough0 (0%)2 (6%)2 (3%)
Pharyngolaryngeal pain2 (6%)0 (0%)2 (3%)
Dysmenorrhea2 (6%)0 (0%)2 (3%)

Postmarketing Experience

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

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:

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.

What drugs interact with Colazal (balsalazide disodium)?

No Information Provided

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Medically Reviewed on 4/10/2020
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