Mesalazine: anti-inflammatory treatment for colitis and Crohn's

Mesalazine belongs to a group of anti-inflammatory medicines called aminosalicylates. The NHS lists ulcerative colitis, Crohn's disease and other forms of inflammatory bowel disease (IBD) as its uses. It works by reducing swelling and inflammation in the lining of the bowel and can help it heal.

It is only available on prescription, and the formulation chosen depends on which part of the gut is inflamed. Brand names the NHS lists are Asacol, Mezavant, Octasa, Pentasa, Salofalk and Zintasa.

Tablets and granules act from within the gut and are taken once a day or split into two or three smaller doses. Tablets are swallowed whole with water and must not be broken, chewed or crushed, because the coating controls where the medicine is released.

For disease in the lower bowel, suppositories, enemas and rectal foam deliver it directly. Suppositories are typically used once at night or several times a day depending on brand, enemas usually once daily at bedtime with the bowel empty and the liquid kept in for as long as possible, and foam is usually 2 full applicators once before bed.

• The dose varies by condition, brand and phase of treatment; once symptoms improve it is likely to be reduced, and children receive weight-based doses.

• Do not stop mesalazine unless your doctor tells you to.

• Missed a dose? Take it when you remember unless the next is near, then skip it; never double up.

• One extra dose is unlikely to harm, but call NHS 111 if you took more than one extra or feel unwell after one.

Mesalazine can occasionally affect the kidneys, so blood, liver and kidney tests are done before treatment begins. The NHS says these checks usually happen about every 3 months in the first year and then yearly, adjusted to your doctor's advice.

Drinking plenty of fluid helps protect the kidneys. The medicine is suitable for long-term use as long as that monitoring continues.

Most adults and children aged 5 and over can take mesalazine. Tell your doctor if you have had an allergic reaction to mesalazine, aspirin or related salicylates, a history of kidney problems (including with sulfasalazine), liver problems, or a severe skin reaction such as peeling, blistering or mouth sores with mesalazine. Also mention pregnancy, trying for a baby or breastfeeding.

More common effects, affecting more than 1 in 100 people, are indigestion or wind, stomach pain, nausea or vomiting, diarrhoea and headaches. Small simple meals, fluids, and a heat pad for stomach pain are the usual self-care steps.

Rarer effects need prompt action. Call NHS 111 for unexplained bleeding, bruising, a sore throat or high temperature, signs of infection, changes in urine or sudden abdominal pain, yellow skin or eyes with dark urine, abdominal and back pain with fever and vomiting, or severe headaches, vision changes, tinnitus or dizziness. Call 999 for chest pain, a severe blistering rash (stop the medicine) or a serious allergic reaction.

Suspected side effects can be reported through the Yellow Card scheme.

Mesalazine can usually be continued in pregnancy, as there is no evidence it harms the baby and uncontrolled bowel inflammation is itself a risk; do not stop it without talking to your doctor. It is generally acceptable while breastfeeding, though rare cases of diarrhoea in babies have been reported. There is no evidence it lowers fertility.

The NHS names laxatives such as lactulose (which can affect how well mesalazine works), the thiopurines azathioprine, mercaptopurine and thioguanine, anti-inflammatory painkillers such as aspirin and ibuprofen (which affect the kidneys), and warfarin. Tell your pharmacist about everything you take.

Alcohol is allowed within the national guidance of 14 units a week, though it can irritate the gut and worsen symptoms. Mesalazine is unlikely to affect driving, cycling or using tools. Eat normally unless your IBD team has given specific dietary advice, and favour simple meals if you feel sick.

Support and information for people with these conditions is available from the charity Crohn's & Colitis UK.