Last updated on RxList: 10/19/2020
Colazal Side Effects Center

What Is Colazal?

Colazal (balsalazide) is an anti-inflammatory drug used to treat active ulcerative colitis. Colazal is available in generic form.

What Are Side Effects of Colazal?

Common side effects of Colazal include:

Infrequently, Colazal can worsen ulcerative colitis. Tell your doctor if your symptoms worsen after starting this medication. Tell your doctor if you have rare but very serious side effects of Colazal including:

  • changes in the amount of urine,
  • yellowing eyes or skin,
  • dark urine,
  • unusual or extreme tiredness,
  • severe stomach or abdominal pain,
  • persistent nausea or vomiting,
  • burning or painful urination, or
  • fast or pounding heartbeat.

Dosage for Colazal

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.

What Drugs, Substances, or Supplements Interact with Colazal?

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.

Colazal During Pregnancy and Breastfeeding

During pregnancy, Colazal should be used only when prescribed. It is not known if this medication passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

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.


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

Call your doctor at once if you have:

  • pain or burning when you urinate;
  • worsening colitis symptoms--fever, stomach pain, cramps, or bloody diarrhea;
  • kidney problems--little or no urinating, swelling, rapid weight gain;
  • liver problems--upper stomach pain, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
  • low red blood cells (anemia)--pale skin, unusual tiredness, feeling light-headed or short of breath, cold hands and feet.

Common side effects may include:

  • headache;
  • mild or occasional nausea, vomiting, stomach pain, diarrhea;
  • joint pain;
  • fever; or
  • cold symptoms such as stuffy nose, sneezing, sore throat.

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)


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Colazal Professional Information


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 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 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 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. 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.

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

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