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Colazal Side Effects

Generic name: balsalazide

Medically reviewed by Philip Thornton, DipPharm. Last updated on Jan 25, 2023.

Note: This document contains side effect information about balsalazide. Some dosage forms listed on this page may not apply to the brand name Colazal.

Applies to balsalazide: oral capsule.

Serious side effects of Colazal

Along with its needed effects, balsalazide (the active ingredient contained in Colazal) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking balsalazide:

More common

  • Agitation
  • bloody diarrhea
  • blood in the urine
  • coma
  • confusion
  • dark-colored urine
  • decreased urine output
  • depression
  • dizziness
  • fever
  • headache
  • hostility
  • increased sensitivity of the skin to sunlight
  • irritability
  • itching, skin rash
  • lethargy
  • light-colored stools
  • muscle twitching
  • nausea
  • pain in the groin or genitals
  • rapid weight gain
  • redness or other discoloration of the skin
  • seizures
  • severe sunburn
  • sharp back pain just below ribs
  • stomach pain
  • swelling of the face, ankles, or hands
  • unusual tiredness or weakness
  • vomiting
  • yellow eyes or skin

Less common

  • Bladder pain
  • cloudy urine
  • difficult, burning, or painful urination
  • frequent urge to urinate
  • heavy bleeding
  • lower back or side pain
  • pale skin
  • trouble breathing
  • unusual bleeding or bruising


  • Chest tightness

Incidence not known

  • Black, tarry stools
  • blistering, peeling, or loosening of the skin
  • chest pain
  • chills
  • clay colored stools
  • cough
  • decreased appetite
  • dizziness
  • increased blood pressure
  • increased thirst
  • joint or muscle pain
  • loss of appetite
  • red, irritated eyes
  • red skin lesions, often with a purple center
  • sores, ulcers, or white spots in the mouth or on the lips
  • swelling of the ,fingers, feet, or lower legs
  • unpleasant breath odor
  • vomiting of blood
  • weight gain

Other side effects of Colazal

Some side effects of balsalazide may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Less common

  • Acid or sour stomach
  • belching
  • bloated or full feeling
  • body aches or pain
  • bone pain
  • congestion
  • constipation
  • coughing
  • cramps
  • difficulty with moving
  • dry mouth
  • dryness of the throat
  • excess air or gas in the stomach or bowels
  • general feeling of discomfort or illness
  • heartburn
  • hoarseness
  • indigestion
  • muscle stiffness
  • passing of gas
  • shivering
  • sleeplessness
  • sneezing
  • stomach discomfort or upset
  • sweating
  • swelling or inflammation of the mouth
  • swollen joints
  • tender, swollen glands in the neck
  • trouble with sleeping
  • trouble with swallowing
  • unable to sleep
  • voice changes
  • weight loss


  • Back pain
  • ear congestion
  • loss of voice
  • pain in the ankles or knees
  • painful, red lumps under the skin, mostly on the legs
  • unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness

Incidence not known

  • Loss or thinning of the hair

For Healthcare Professionals

Applies to balsalazide: oral capsule, oral tablet.


Very common (10% or more): Abdominal pain upper (17%), vomiting (17%), abdominal pain (12%), diarrhea (11%)

Common (1% to 10%): Flatulence, dyspepsia, dry mouth, constipation, colitis ulcerative, hematochezia, nausea, stomatitis

Frequency not reported: Defecation urgency, hard feces, gastroesophageal reflux disease, gastroenteritis

Postmarketing reports: Pancreatitis[Ref]

Nervous system

Very common (10% or more): Headache (15%)

Frequency not reported: Dizziness, lethargy[Ref]


Very common (10% or more): Pyrexia (11%)

Common (1% to 10%): Fatigue, fever, flu-like disorder, pyrexia

Frequency not reported: Malaise, pain, pyrexia[Ref]


Common (1% to 10%): Arthralgia, musculoskeletal pain, myalgia, cramps

Frequency not reported: Back pain[Ref]


Common (1% to 10%): Pharyngolaryngeal pain, coughing

Postmarketing reports: Alveolitis, pleural effusion[Ref]


Frequency not reported: Increased aspartate aminotransferase

Postmarketing reports: Elevated liver enzymes (AST, ALT, GGT, LDH, alkaline phosphatase), elevated bilirubin, jaundice, cholestatic jaundice, cirrhosis, hepatocellular damage including liver necrosis and liver failure, Kawasaki-like syndrome including hepatic dysfunction[Ref]


Common (1% to 10%): Anemia[Ref]


Frequency not reported: Increased blood pressure, increased heart rate

Postmarketing reports: Myocarditis, pericarditis, vasculitis[Ref]


Postmarketing reports: Renal failure, interstitial nephritis[Ref]


Frequency not reported: Erythema nodosum, rash, face edema

Postmarketing reports: Alopecia, pruritus[Ref]


Common (1% to 10%): Nasopharyngitis, rhinitis, pharyngitis, urinary tract infection, influenza

Frequency not reported: Upper respiratory infection

Postmarketing reports: Pneumonia (with and without eosinophilia)[Ref]


Common (1% to 10%): Anorexia[Ref]


Common (1% to 10%): Insomnia[Ref]


Common (1% to 10%): Dysmenorrhea[Ref]


1. "Product Information. Colazal (balsalazide)." Salix Pharmaceuticals (2001):

2. "Product Information. Giazo (balsalazide)." Valeant Pharmaceuticals (2018):

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.