5-aminosalicylate Pregnancy: Should be used during pregnancy only if the potential benefit justifies the potential risk to the foetus — animal studies showed fetal developmental toxicity, and there are no adequate and well-controlled studies in pregnant women; a risk of stillbirth or pre-term birth is reported but with no substantial risk of malformation. Small amounts of the active metabolite (5-ASA) may pass into breast milk and harmful infant effects (diarrhoea) have been reported — olsalazine should not be taken by breast-feeding women unless the benefit outweighs the risks.

Olsalazine sodium

Brand names: Dipentum

Olsalazine is an aminosalicylate used to treat mild ulcerative colitis and to maintain remission.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Acute mild disease (adults including the elderly): commence on 1 g daily in divided doses taken at the end of meals. Depending on the patient's response, the dose may be titrated upwards over a period of one week

Route: Oral — take at the end of a meal (taking olsalazine on an empty stomach may sometimes lead to loose stools or diarrhoea)

Frequency: Daily in divided doses, at the end of meals

Max: 3 g daily; a single dose should not exceed 1 g

Remission (adults including the elderly): 0.5 g twice daily, taken at the end of meals. Olsalazine has been used concomitantly with glucocorticosteroids. Baseline renal function measurement is required in all patients initiating treatment; monitor renal function by estimating serum creatinine before treatment, every 3 months for the first year, every 6 months for the next 4 years, and annually after 5 years, discontinuing if renal function deteriorates (§4.4). Perform haematological investigations if the patient develops unexplained bleeding, bruising, purpura, anaemia, fever, sore throat or mouth ulcers, and stop treatment if a blood dyscrasia is suspected or evident. Patients with severe allergy or asthma should be observed for worsening of these conditions. The eMC SPC states no paediatric dose; the US label (Dipentum) states safety and effectiveness in paediatric patients have not been established. Cross-check only — the US label gives a recommended dosage of 500 mg orally twice daily; the UK SPC regimen above was used.

Dose adjustments

Renal

Contraindicated in significant renal impairment. Baseline renal function measurement is required in all patients initiating treatment; for patients with baseline renal impairment, initiate only if the benefits are considered to outweigh the risk, with periodic renal function monitoring, especially in the early months. Discontinue if renal function deteriorates.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to olsalazine or other salicylates, or to any of the excipients
Significant renal impairment (no experience of use in these patients)

Side effects

Diarrhoea — the most common side effect, usually transient (common); managed by taking the drug at the end of a more substantial meal, dose titration or dose reduction, and stopping the drug if it persists
Nausea (common); vomiting and dyspepsia (uncommon)
Headache (common); dizziness and paraesthesia (uncommon)
Rash (common); pruritus, alopecia, photosensitivity reaction and urticaria (uncommon)
Arthralgia (common); hepatic enzyme increased and thrombocytopenia (uncommon); very rare serious blood dyscrasias including aplastic anaemia, agranulocytosis-type pictures, neutropenia and pancytopenia (frequency not known)

Interactions

Low molecular weight heparins or heparinoids — coadministration with salicylates may increase the risk of bleeding, more specifically haematomas following neuraxial anaesthesia; discontinue salicylates before initiation, or monitor closely for bleeding if this is not possible
Warfarin — increased prothrombin time has been reported in patients taking concomitant warfarin
6-mercaptopurine — increased risk of myelosuppression; use the lowest possible doses of each drug and monitor, especially for leukopenia
Thioguanine — increased risk of myelosuppression; careful monitoring of blood counts is recommended
Varicella vaccine — do not give salicylates for six weeks after vaccination, to avoid a possible increased risk of Reye's syndrome

Clinical monograph

How it works

It consists of two molecules of mesalazine linked by an azo bond that is cleaved by colonic bacteria, releasing mesalazine to act topically on inflamed bowel mucosa.

Prescribing in practice

Watch for blood dyscrasias and advise patients to report unexplained bleeding, bruising, sore throat or fever for prompt blood count assessment.
Watery diarrhoea is a recognised effect that may be reduced by taking doses with food.
Use cautiously in renal impairment given the nephrotoxic potential of aminosalicylates.

Monitoring

Monitor renal function and full blood count during treatment, and review for any deterioration in bowel symptoms.

Counselling the patient

Advise patients to take the medicine with food and to report persistent watery diarrhoea.
Tell patients to seek prompt advice if they develop a sore throat, fever, bruising or unexplained bleeding.

Evidence & guidelines

Aminosalicylates such as olsalazine are established treatments for ulcerative colitis, used in accordance with NICE guidance and current prescribing references.

Reference: NICE NG130; 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).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways