Mesalazine

Mesalazine is one of a group of medicines called aminosalicylates, or 5-ASAs. It has been used for inflammatory bowel disease (IBD) for more than 40 years and, for most people, causes few side effects.

What is it and how does it work?

Mesalazine reduces inflammation in the lining of the bowel. It acts directly on the bowel wall rather than throughout the body, which is why it is generally well tolerated. The different brands are designed to release the medicine in different parts of the gut, mainly in the colon.

What is it used for?

• Ulcerative colitis (UC). Mesalazine is the first treatment for mild to moderate UC. It is used to settle a flare-up and then, usually at a lower dose, to keep the disease in remission long term. Taken regularly, it also appears to reduce the long-term risk of bowel cancer in UC.
• Crohn’s disease (CD). It is much less effective in CD and is now used less often, although some people with mild CD of the colon are still prescribed it.

Brands and forms

Mesalazine is sold under several brand names, including Asacol, Octasa, Pentasa, Salofalk, Mezavant and Zintasa. It comes in several forms:

• Tablets or capsules, swallowed whole, never crushed or chewed, because the coating controls where the medicine is released.
• Granules, which can be easier to take in larger doses.
• Suppositories, for inflammation in the rectum (proctitis).
• Liquid or foam enemas, for inflammation in the rectum and lower colon.

Tablets and rectal treatments are often used together, as this works better than either alone for disease in the lower colon.

Because the brands release the medicine in different ways, they are not interchangeable. You should stay on the same brand unless your IBD team decides to change it, and check that your pharmacy gives you the brand you are used to.

How is it taken?

Your doctor will tell you the dose. Many people now take their tablets or granules once a day, which works as well as divided doses and is easier to remember. It usually takes two to four weeks to see an improvement.

The most important thing is to keep taking it every day, even when you feel well. Missing doses is one of the commonest reasons for a relapse of UC.

You may sometimes see what looks like a tablet in your motions. This is usually just the empty coating, the medicine having been released. If you often see whole, undissolved tablets, tell your IBD team, as a different brand may suit you better.

Blood tests

Very rarely, mesalazine can affect the kidneys. You will have a blood test to check your kidney function before you start, again after a few months, and then usually once a year for as long as you take it.

Side effects

Most people have no side effects. The more common ones, which often settle, are:

• Headache
• Nausea or indigestion
• Abdominal pain or diarrhoea
• Rash

Rarely, mesalazine causes a worsening of colitis symptoms soon after starting, which can be mistaken for a flare-up. Other rare side effects include inflammation of the pancreas, liver, heart or lungs, and kidney problems.

Stop taking it and contact your doctor at once if you develop an unexplained sore throat, fever, mouth ulcers, bruising or bleeding, as you may need a blood test.

You should not take mesalazine if you are allergic to aspirin or other salicylates, or if you have severe kidney problems.

Pregnancy and breastfeeding

Mesalazine is considered safe in pregnancy and while breastfeeding. Keeping UC under control is important for both mother and baby, so do not stop it without advice. See Pregnancy and Inflammatory Bowel Disease.

Sulfasalazine

Sulfasalazine (Salazopyrin) is the original medicine of this group. It is made of mesalazine joined to a sulphonamide, which causes more side effects, including headache, nausea and rash. It also turns urine orange-yellow, can stain soft contact lenses, and can temporarily reduce sperm count in men, which recovers when it is stopped. It is now used mainly by people who have taken it successfully for many years, and by people who also have arthritis, which it can help.

If mesalazine is not enough

If UC is not controlled with mesalazine, your IBD team may suggest a course of steroids or, for longer-term control, an immunosuppressant such as azathioprine or a biologic medicine. See Medicines for Crohn’s Disease and Ulcerative Colitis and Treatment of Ulcerative Colitis.

Never stop taking mesalazine without discussing it with your IBD team first.