Mesalazine
2 medicines
Mesalazine is a 5-ASA anti-inflammatory used to treat and maintain remission of ulcerative colitis. Rare kidney injury means periodic kidney function tests are needed, and rarely it can paradoxically worsen colitis symptoms.
Key facts
- Mesalazine (also called mesalamine, sold as Asacol, Pentasa, Salofalk and other brands) is an anti-inflammatory drug from the 5-aminosalicylic acid (5-ASA) group, used mainly for ulcerative colitis.
- It comes as tablets, granules, suppositories, and enemas, chosen by which part of the bowel is affected. It is taken regularly, including during remission, to prevent flare-ups.
- Kidney injury is a rare but recognized risk, so your kidney function is checked before starting and periodically during treatment, especially if treatment continues for years.
- Seek urgent care if diarrhoea, abdominal pain, cramping or bloody stools get worse soon after starting mesalazine. Rarely, mesalazine itself can cause a reaction that mimics a colitis flare, so stopping and getting reviewed is important rather than assuming the disease has worsened.
What mesalazine treats
Mesalazine treats active mild to moderate ulcerative colitis and is continued at a lower dose to maintain remission. Certain formulations are also used for mild Crohn's disease affecting the colon. Suppositories and enemas target inflammation in the rectum and lower bowel, while oral forms are coated or timed to release further along the digestive tract.
How mesalazine works
Ulcerative colitis involves ongoing inflammation of the lining of the colon and rectum. Mesalazine acts directly on the gut lining it passes over or reaches, reducing the production of inflammatory chemicals in the bowel wall. Because it works locally within the gut rather than throughout the body, the formulation and release site matter for how well it reaches the inflamed area.
Before you take it
- Tell your prescriber about any kidney disease, since mesalazine needs caution or dose adjustment if your kidneys do not work normally.
- Tell your prescriber about aspirin allergy or sensitivity, as mesalazine is chemically related to aspirin.
- Mention all other medicines, including azathioprine and other inflammatory bowel disease treatments, so interactions can be reviewed.
Side effects
Common effects: headache, nausea, abdominal pain, and diarrhoea.
Seek urgent medical care for:
- Worsening bloody diarrhoea, severe cramping, or fever soon after starting or increasing the dose. This can, rarely, be mesalazine-induced colitis rather than a flare of the underlying disease.
- Reduced urine output, swelling of the legs, or unusual tiredness, which can signal kidney injury.
- Unexplained bruising or bleeding, or signs of a blood disorder.
- Chest pain, breathlessness, or signs of an allergic reaction such as rash or facial swelling.
Safety essentials
- Have your kidney function tested before starting mesalazine and at regular intervals throughout treatment, even when you feel well, since kidney injury can develop silently.
- If your bowel symptoms worsen shortly after starting or changing the dose, tell your prescriber promptly. Mesalazine can rarely cause a paradoxical worsening of colitis, easy to mistake for a disease flare; the right response is to stop and get reviewed, not to increase the dose.
- Keep taking maintenance treatment during remission as prescribed; stopping increases the risk of relapse.
This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.