An aminosalicylate (5-ASA)
Mesalazine
An anti-inflammatory medicine that acts directly on the bowel lining to treat and prevent flares of ulcerative colitis.
What is Mesalazine?
Mesalazine is an aminosalicylate (5-ASA) used to treat and prevent flares of ulcerative colitis, a form of inflammatory bowel disease. It works directly on the lining of the bowel to calm inflammation. It is taken regularly even when symptoms have settled, and is available as tablets, granules and forms used into the back passage.
Education and reference only. This is a plain-language guide to Mesalazine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Mesalazine is an aminosalicylate, also known as 5-ASA, used mainly in inflammatory bowel disease — particularly ulcerative colitis. It is used both to settle an active flare and, importantly, to keep the disease in remission so that flares are less likely. Rather than acting throughout the body, it works locally on the inflamed lining of the bowel, and different formulations and ways of taking it are designed to deliver the medicine to the part of the bowel that is affected.
How it works
Mesalazine acts directly on the lining of the bowel to damp down inflammation, rather than working through the bloodstream like many medicines. It is thought to interrupt several of the inflammatory signals and processes in the gut wall and to act as an antioxidant locally. Because its job is to reach the inflamed bowel, the various tablets, granules, suppositories and enemas are formulated to release or deliver the medicine to the right part of the gut — the small bowel, the colon, or the lower bowel and rectum.
Company & origin
Originated / developed by: Various manufacturers.
Mesalazine is 5-aminosalicylic acid (5-ASA), the active anti-inflammatory part of the older drug sulfasalazine. It was developed so that the active component could be delivered to the bowel without the sulfa part of sulfasalazine, which caused many of that drug's side effects.
Practical use
How to take Mesalazine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it regularly, even when you feel completely well — it keeps ulcerative colitis in remission and reduces the chance of a flare, so it is not a medicine to take only during symptoms.
- Swallow modified-release tablets whole and take granules as directed (often without chewing), as they are designed to release the medicine in the right part of the bowel.
- If you use a suppository or enema form, follow the technique shown for delivering it into the back passage, usually at a quiet time such as bedtime.
- Report any unexplained bruising, bleeding, sore throat, fever or feeling generally unwell, as rarely mesalazine can affect the blood count (blood dyscrasia).
- Tell your team if your bowel symptoms worsen, as a flare may need a change of treatment.
- Attend for blood and urine tests as arranged, as kidney function is monitored while taking it.
Weighing it up
Advantages & disadvantages of Mesalazine
Advantages
- Effective at both settling flares and keeping ulcerative colitis in remission, with long-term use reducing how often flares occur.
- Works locally on the bowel, so it generally avoids the wider side effects of steroids and stronger immune-suppressing medicines.
- Available in many forms — tablets, granules, suppositories and enemas — so treatment can be matched to the part of the bowel affected.
- Long-term use is also linked with a lower risk of bowel cancer in ulcerative colitis.
Disadvantages
- Must be taken consistently, including when well, to keep working — missed doses risk a flare.
- Rarely can affect the blood count or the kidneys, so monitoring and prompt reporting of warning signs are needed.
- Can cause digestive upset or headache, and occasionally a flare-like worsening that can be mistaken for the disease itself.
- Several different formulations are not always interchangeable, so switching brands should be done with advice.
Practical use
Good to know
Mesalazine is a maintenance medicine as much as a treatment — taking it regularly, even when you feel completely well, is what keeps ulcerative colitis in remission and reduces the chance of a flare. Modified-release tablets and granules are made to release the medicine in the right place, so they should be swallowed or taken as directed and not crushed. Forms used into the back passage (suppositories and enemas) are useful when the lower bowel is mainly affected. Rarely, mesalazine can affect the blood count, so any unexplained bruising, bleeding, sore throat or fever should be reported, and it can affect the kidneys, so kidney function is checked over time.
Who should not take it / use with caution
- People with a known allergy to mesalazine, aspirin or other salicylates.
- People with significantly reduced kidney function, where it is used with particular caution and close monitoring, and those with a history of certain blood disorders.
- Used with caution in pregnancy and breastfeeding (often continued when needed under specialist advice) and in active stomach or duodenal ulcers.
Monitoring
- Kidney function (blood and urine tests) before and during treatment
- Full blood count if signs of a blood problem appear
- Bowel symptoms and response to treatment
Side effects
- Headache, nausea, tummy pain, wind, and diarrhoea or a worsening of bowel symptoms.
- Skin rash; rarely inflammation around the heart or lungs causing chest pain or breathlessness, which should be reported.
- Rarely, effects on the blood count (bruising, bleeding, sore throat, fever) or on the kidneys — both important to report and monitor.
Key interactions
- Care with other medicines that can affect the kidneys, such as anti-inflammatory painkillers (NSAIDs).
- May add to the effect of azathioprine or mercaptopurine on the blood count when used together.
- Some formulations can be affected by medicines that change the acidity of the gut, which may alter where the medicine is released.
Available as: Modified-release tablets and granules taken by mouth, and suppositories and enemas used into the back passage for disease affecting the lower bowel.
Answers
Mesalazine: frequently asked questions
Do I have to keep taking mesalazine when I feel well?
Yes. Mesalazine is a maintenance medicine — taking it regularly, even with no symptoms, is what keeps ulcerative colitis in remission and lowers the chance of a flare. Stopping when you feel well makes a flare more likely, so keep taking it unless your team advises otherwise.
Why must I report bruising, bleeding or a sore throat?
Rarely, mesalazine can affect the cells the bone marrow makes, lowering the blood count (a blood dyscrasia). Unexplained bruising or bleeding, a persistent sore throat, fever or feeling generally unwell can be early signs, so report them promptly so a blood test can be done.
Can I crush the tablets or open the granules?
Modified-release tablets should be swallowed whole, and granules taken as directed, because they are designed to release the medicine in the right part of the bowel. Crushing or chewing can release it in the wrong place. Ask your pharmacist if you have trouble swallowing them.
Are the different brands of mesalazine the same?
They all contain mesalazine, but the formulations release the medicine in different ways and amounts along the bowel, so they are not always directly interchangeable. If a switch is needed, it should be done with your prescriber's advice rather than swapped at the pharmacy.
Why do I need kidney tests on mesalazine?
Mesalazine can, uncommonly, affect the kidneys, so kidney function is checked before starting and from time to time during treatment. This monitoring picks up any change early, and urine tests may also be used as part of the checks.
The wider class
About Aminosalicylates
Mesalazine belongs to the aminosalicylates class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF: Aminosalicylates (mesalazine).
- NICE CKS: Mesalazine.
- NICE: Ulcerative colitis: management (NG130).
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