5-ASA prodrug
Pregnancy: Contraindicated. UK SPC §4.3 lists 'Pregnant and breast feeding women' as a contraindication. §4.6 Pregnancy: 'Human experience with balsalazide is limited, therefore Colazide should not be given to pregnant women.' Breast-feeding: 'Colazide should not be given to breast feeding women as the active metabolite mesalazine has produced adverse effects in nursing infants.' Fertility: 'Animal studies on fertility and reproductive function did not reveal adverse effects of balsalazide.'
Balsalazide sodium
Brand names: Colazide
Balsalazide is an aminosalicylate prodrug used to treat mild to moderate ulcerative colitis and to maintain remission.
Adult dose
Dose: Active ulcerative colitis: 2.25 g balsalazide disodium (3 capsules) three times daily, i.e. 6.75 g daily, continued until remission or for 12 weeks maximum. Rectal or oral steroids can be given concomitantly if necessary. Maintenance: starting dose 1.5 g (two capsules) twice daily, i.e. 3 g daily, adjusted to response — the SPC notes there may be additional benefit with a dose up to 6 g daily.
Route: Oral — capsules swallowed whole with or after food (§4.5 notes systemic exposure to balsalazide and its metabolites may be increased in the fasting compared with the fed state, so it should preferably be given with food)
Frequency: Active disease: three times daily. Maintenance: twice daily
Max: Active disease: 6.75 g balsalazide disodium daily (2.25 g three times daily), for a maximum of 12 weeks. Maintenance is a separate, lower regimen with its own stated upper figure of 6 g daily — do not apply the maintenance figure as a ceiling on the active-disease regimen.
Verbatim source wording (UK SPC §4.2, Posology, Adults): 'Treatment of active disease: 2.25g Balsalazide disodium (3 capsules) three times daily (6.75g daily) until remission or for 12 weeks maximum. Rectal or oral steroids can be given concomitantly if necessary. Maintenance treatment: The recommended starting dose is 1.5g Balsalazide disodium (2 capsules) twice daily (3g daily). The dose can be adjusted based on each patient's response; there may be an additional benefit with a dose up to 6g daily.' Elderly, verbatim: 'No dose adjustment is anticipated.' Method of administration, verbatim: 'To be swallowed whole with or after food.' CAPSULE STRENGTH: §4.2 counts capsules, not milligrams per capsule — the 750 mg strength comes from the sourced product's own name, 'Colazide 750mg Capsules', and 3 capsules x 750 mg = 2.25 g, which matches §4.2's own arithmetic. CHECK THE STRENGTH OF THE CAPSULE IN YOUR HAND before converting a gram dose into a capsule count. MAXDOSE CARE: the active-disease regimen (6.75 g/day) is HIGHER than the maintenance upper figure (6 g/day); the two must not be conflated, and the maintenance figure must never be recorded as a ceiling on active-disease dosing. INDICATION: the SPC's dosing is for ulcerative colitis (active disease then maintenance); no other indication is dosed in the retrieved §4.2. PAEDIATRIC: paedDose is null because §4.2 states, verbatim, 'Colazide is not recommended in children.'
Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.
Contraindications
- Hypersensitivity to the active substance, to its metabolites including mesalazine, or to any of the excipients listed in section 6.1 (§4.3)
- History of hypersensitivity to salicylates (§4.3)
- Severe hepatic impairment (§4.3)
- Moderate to severe renal impairment (§4.3)
- Pregnant and breast feeding women (§4.3)
- Not recommended in children (§4.2)
- Use with caution (not a contraindication, §4.4): asthma, bleeding disorders, active ulcer disease, mild renal impairment, or established hepatic disease
Side effects
- The SPC states the adverse effects 'are expected to be those of mesalazine' and lists the reactions reported with oral mesalazine (§4.8)
- Blood and lymphatic system disorders (§4.8): blood dyscrasias, aplastic anaemia, leucopenia, neutropenia, agranulocytosis, thrombocytopenia
- Gastrointestinal disorders (§4.8): abdominal pain, diarrhoea, nausea, vomiting, aggravation of ulcerative colitis, acute pancreatitis
- Renal and urinary disorders (§4.8): interstitial nephritis, acute renal failure, renal insufficiency, renal impairment
- Nervous system disorders (§4.8): headache, neuropathy
- Cardiac disorders (§4.8): myocarditis, pericarditis
- Respiratory, thoracic and mediastinal disorders (§4.8): bronchospasm, allergic alveolitis, eosinophilic pneumonia
- Hepatobiliary disorders (§4.8): hepatitis, cholelithiasis
- Skin and subcutaneous tissue disorders (§4.8): alopecia, angioedema, rash
- Musculoskeletal and connective tissue disorders (§4.8): systemic lupus erythematosus-like syndrome, arthralgia, myalgia
- Immune system disorders (§4.8): hypersensitivity
Interactions
- No formal interaction studies have been performed with Colazide (§4.5)
- Food (§4.5): systemically available amounts of balsalazide and its metabolites may be increased in the fasting compared with the fed state — give preferably with food
- Drugs eliminated by active renal tubular secretion (§4.5): 'plasma levels of co-prescribed drugs also eliminated by this route may be raised and this should be noted in the case of those with a narrow therapeutic range, such as methotrexate'
- Digoxin (§4.5): uptake has been impaired in some individuals by concomitant sulphasalazine; monitor digoxin plasma levels in digitalised patients starting Colazide
- Azathioprine or 6-mercaptopurine (§4.5): 'Mesalazine inhibits thiopurine methyltransferase... caution is recommended for concurrent use of mesalazine as this can increase the potential for blood dyscrasias'
- Classical acetylsalicylic-acid-type salicylate interactions are considered very unlikely despite the salicylate chemistry (§4.5)
Monitoring
- Renal function (§4.4): 'Renal function should be monitored before starting an oral aminosalicylate, at 3 months of treatment, and then annually during treatment (more frequently in renal impairment).'
- Blood counts, BUN/creatinine and urine analysis should be performed during treatment (§4.4)
- Patient safety-netting (§4.4): 'Patients receiving aminosalicylates should be advised to report any unexplained bleeding, bruising, purpura, sore throat, fever or malaise that occurs during treatment. A blood count should be performed and the drug stopped immediately if there is suspicion of a blood dyscrasia.'
- Digoxin (§4.5): 'it is recommended that plasma levels of digoxin should be monitored in digitalised patients starting Colazide'
- Duration limit: active-disease treatment runs until remission or for 12 weeks maximum (§4.2)
Clinical monograph
How it works
It is a prodrug that is cleaved by colonic bacteria to release the active moiety mesalazine (5-aminosalicylic acid) directly in the colon, where it exerts a topical anti-inflammatory effect on the bowel mucosa.
Prescribing in practice
- Aminosalicylates can cause blood dyscrasias, and patients should be advised to report unexplained bleeding, bruising, sore throat, fever or malaise that may indicate a blood disorder requiring a full blood count.
- Renal function should be assessed before and during treatment because mesalazine-related nephrotoxicity, including interstitial nephritis, can occur.
- Use with caution in patients with salicylate hypersensitivity, and be aware that mesalazine-induced cardiac hypersensitivity and acute intolerance reactions can occur.
Monitoring
Monitor renal function before starting and periodically during treatment, and check a full blood count if a blood dyscrasia is suspected.
Counselling the patient
- Keep taking it as prescribed, including for maintenance, even when you feel well.
- Report unexplained bruising, bleeding, sore throat or fever straight away.
- Tell your prescriber if you have a history of aspirin or salicylate allergy.
Evidence & guidelines
Oral aminosalicylates are recommended first-line in NICE guidance for inducing and maintaining remission in mild to moderate ulcerative colitis.
Reference: NICE NG130; BSG IBD; ECCO; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.
Calculators