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Mesalazine - Brand names: Asacol, Mezavant, Octasa, Pentasa, Salofalk, Zintasa

On this page

  1. About mesalazine
  2. Key facts
  3. Who can and cannot take mesalazine
  4. How and when to take mesalazine
  5. Side effects
  6. How to cope with side effects of mesalazine
  7. Pregnancy and breastfeeding
  8. Cautions with other medicines
  9. Common questions about mesalazine

1. About mesalazine

Mesalazine is used to treat ulcerative colitis and Crohn's disease and other types of inflammatory bowel disease.

It belongs to a group of medicines called aminosalicylates. These help to reduce redness and swelling (inflammation) and can help with healing.

Some people take mesalazine together with steroids.

Mesalazine is only available on prescription. It comes as:

  • tablets
  • granules
  • rectal foam
  • suppositories
  • enemas

2. Key facts

  • Different brands of mesalazine tablets and granules work on different parts of your gut. Rectal foam, suppositories or enemas are prescribed for the lower part of your gut.
  • Once you and your doctor find a brand of mesalazine that works for you, it's usually best to stick to the same one.
  • When your symptoms are under control you can usually go onto a lower dose.
  • Common side effects of mesalazine include upset stomach, and muscle aches and pains.
  • One very rare side effect can be problems with your blood. Tell your doctor immediately if you get unexplained bleeding, bruising or red or purple marks on your skin, or if you have a sore throat, high temperature or feel generally unwell.

3. Who can and cannot take mesalazine

Adults and children aged 5 years and older can take mesalazine.

Mesalazine may not be suitable for some people. To make sure it's safe for you, tell a pharmacist or doctor before taking or using it if you:

  • have ever had an allergic reaction to mesalazine, aspirin, or any other salicylates such as methylsalicylate or choline salicylate
  • have ever had an allergic reaction to any other medicine
  • have any problems with your kidneys or liver
  • have a rare blood condition called porphyria
  • are trying to get pregnant, already pregnant, or breastfeeding

4. How and when to take mesalazine

Always follow the instructions from a pharmacist or doctor, or the leaflet that comes with your medicine.


Your dose will depend on why you need it and on the type and brand of mesalazine that your doctor has prescribed for you. It also depends on whether you are taking it for a short or long time.

For children, the dose may be lower, and it is calculated according to their weight.

How to take tablets and granules

You will either take the tablets or granules once a day, or as 2 or 3 smaller doses throughout the day.

Swallow the tablets whole with a drink of water or juice. Do not break, chew or crush them. This is because some tablets have a special coating to delay when they start to work, or to protect the medicine from the acids in your stomach.

For granules, open the sachet and tip the granules onto your tongue. Swallow them whole with a drink of water or juice. Do not chew them, as some granules have a special coating.

You can take some brands with food. Check the leaflet that comes with your medicine.

If you're also taking indigestion medicines or remedies, leave a 2 hour gap before and after taking mesalazine. Indigestion treatments can affect how well the medicine works.

How to use suppositories

Your doctor or pharmacist will tell you how many suppositories to use each day. Some types you use once a day before you go to bed, and others you use several times a day with the last dose before you go to bed. Use them after you do a poo.

  1. Wash your hands before and after using the suppository. Also clean around your bottom (anus) with mild soap and water, rinse and pat dry.
  2. Unwrap the suppository.
  3. Gently push the suppository into your anus with the pointed end first. It needs to go in about 3 centimetres (1 inch).
  4. Sit or lie still for about 15 minutes. The suppository will start to soften, as it melts with your body heat. This is normal.

Try not to do a poo for at least an hour after using a suppository. This gives the medicine time to work.

How to use enemas

You will usually use mesalazine enemas once a day before you go to bed.

Use the enema after doing a poo. This is because the medicine works best when your bowels are empty.

  1. Wash your hands before and after using the enema.
  2. Lie on your side, with your bottom slightly higher than the rest of your body. You can use a pillow to lift your bottom up. You may want to lie on a towel.
  3. Put one of the disposable plastic bags provided over your hand (like a glove) and pick up the bottle.
  4. Shake the bottle.
  5. Break the seal on the nozzle, or remove the protective cap.
  6. Gently push the nozzle into your bottom (anus) as far as is comfortable.
  7. Squeeze the bottle steadily to allow the liquid to empty into your anus quite quickly. This takes about 30 to 40 seconds. It's normal for some liquid to be left in the bottle afterwards.
  8. Remove the nozzle from your bottom.
  9. Peel the disposable plastic bag off your hand and use it to cover the bottle, ready to throw away.
  10. Roll onto your front and wait for 5 minutes. This will stop any liquid coming out of your bottom.
  11. For sleeping, find a comfortable position that keeps the liquid in your bottom for as long as possible. The longer it stays there, the better it will work.

How to use rectal foam

You will usually use mesalazine rectal foam once a day before you go to bed. The dose is 2 full applicators.

Use the rectal foam after doing a poo. This is because the medicine works best when your bowels are empty.

After you apply the foam, try not to poo again until the next morning. For the medicine to work properly it needs to stay inside your bowel as long as possible.

First read the instruction leaflet. The pictures show you exactly how to use the foam.

Before using it for the first time, remove the plastic flap (or safety lock) from underneath the dome-shaped pump at the top of the can.

  1. Wash your hands before and after using the foam.
  2. Push a new applicator onto the nozzle. This nozzle sticks out beneath the dome at the top of the can.
  3. Shake the can for about 20 seconds.
  4. There is a rounded gap at the base of the dome. Twist the dome until the gap lines up with the nozzle.
  5. Put your finger on top of the dome and turn the can upside down. The spray will only work properly if you hold the can with the dome pointing straight down.
  6. Either stand with one leg raised on a chair, or lie down on your side with your lower leg stretched out and upper leg bent.
  7. Gently put the tip of the applicator into your anus as far as possible. You may want to use a lubricating jelly on the tip of the applicator.
  8. Push the dome down. This fills the applicator with a dose of foam.
  9. Release the dome very slowly, to push the foam out.
  10. Wait 10 to 15 seconds and then slowly remove the applicator from your bottom. Do this slowly to prevent the foam coming out.
  11. Remove the applicator from the nozzle. Put it in the plastic bag provided and throw the bag away (with your normal household rubbish).

Repeat from step 1 using a new applicator, so that you use 2 full applicators of foam.

Will my dose go up or down?

Once your symptoms start to get better, it's likely that your dose will be reduced. This lower dose is sometimes called a maintenance dose.

Your doctor may want to increase your dose if your symptoms start to get worse again.

What if I forget to take it?

If you miss a dose of mesalazine, take it as soon as you remember, unless it's almost time for your next dose. In this case, skip the missed one and take the next dose at the usual time.

Do not take 2 doses together to make up for a forgotten dose.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Taking too much mesalazine as a one-off is unlikely to cause problems.

Urgent advice: Contact 111 for advice now if:

  • you've taken up to 1 extra dose of mesalazine and you feel unwell
  • you've taken more than double your usual dose of mesalazine, even if you feel well

Go to or call 111.

5. Side effects

Like all medicines, mesalazine can cause side effects, but not everyone gets them.

The higher the dose of mesalazine that you take, the greater the chance of side effects.

Common side effects

Common side effects happen in more than 1 in 100 people. Your risk of getting a particular side effect varies, depending on whether you are prescribed tablets, granules, suppositories, foam or enemas.

Keep taking the medicine, but tell your doctor if these side effects bother you or do not go away:

  • indigestion, stomach pain or wind
  • feeling or being sick (nausea or vomiting)
  • diarrhoea
  • headaches, muscle aches and pains

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people.

Tell your doctor straight away if you get:

  • any unexplained bleeding, an unexplained sore throat or high temperature, bruising, red or purple marks on your skin (these may be less obvious on black or brown skin), or if you feel generally unwell during the treatment – these can be signs of problems with your blood
  • a high temperature, chills, a sore throat, ear or sinus pain, a cough, pain when peeing, mouth sores or a wound that will not heal – these can be signs of an infection
  • a change in the colour of your pee or the amount you pee – these can be signs of kidney problems
  • chest pain, a faster heartbeat or feeling more tired than usual – these can be signs of heart problems
  • yellowing of your eyes or skin (this may be less obvious on black or brown skin), dark pee, stomach pain, high temperature, feeling tired or feeling sick – these can be signs of liver problems
  • back or stomach pain, fever, feeling sick or being sick – these can be signs of an inflamed pancreas

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to mesalazine.

Immediate action required: Call 999 now if:
  • your lips, mouth, throat or tongue suddenly become swollen
  • you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
  • your throat feels tight or you're struggling to swallow
  • your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
  • you suddenly become very confused, drowsy or dizzy
  • someone faints and cannot be woken up
  • a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of mesalazine. For a full list, see the leaflet inside your medicines packet.


You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

6. How to cope with side effects of mesalazine

What to do about:

  • indigestion, stomach pain or wind – try not to eat foods that cause wind (like lentils, peas, beans and onions). Eat smaller meals, and eat and drink slowly. Putting a heat pad or covered hot water bottle on your stomach may also help with stomach pain.
  • feeling or being sick – stick to simple meals and do not eat rich or spicy food. Check the instructions that come with your medicine to see if you can take it after you've eaten. If you're being sick, try having small, frequent sips of water or squash to avoid dehydration. Do not take any other medicines to treat vomiting without speaking to a pharmacist or doctor.
  • diarrhoea – drink plenty of fluids, such as water or squash, to avoid dehydration. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
  • headaches, muscle aches and pains – drink plenty of water and ask your pharmacist to recommend a suitable painkiller. Tell your doctor if the aches continue despite taking painkillers or if they last for more than a few days.

7. Pregnancy and breastfeeding

Mesalazine and pregnancy

You may be advised to continue using mesalazine during pregnancy to make sure that your inflammatory bowel disease remains well controlled. There's no evidence that taking mesalazine in pregnancy harms your baby.

If you become pregnant while taking mesalazine, speak to your doctor. Do not stop taking your medicine unless your doctor tells you to.

Your doctor can explain the risks and benefits of taking mesalazine and will help you choose the best treatment for you and your baby.

Mesalazine and breastfeeding

If your doctor or health visitor says your baby is healthy, then it's usually OK to take mesalazine while breastfeeding.

Small amounts of mesalazine pass into breast milk, and are unlikely to cause any side effects in your baby. Many people have taken mesalazine while breastfeeding without any problems, although there have been some rare cases of diarrhoea in babies.

Tell your midwife, health visitor, pharmacist or doctor as soon as possible if you notice your baby is not feeding as well as usual, or has diarrhoea, or if you have any other concerns about your baby.

Non-urgent advice: Tell your doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. Cautions with other medicines

There are some medicines that affect the way mesalazine works. Tell a pharmacist or doctor if you are taking:

Mixing mesalazine with herbal remedies or supplements

There's very little information about taking herbal remedies and supplements while taking or using mesalazine. Ask a pharmacist for advice.

Important: Medicine safety

Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

9. Common questions about mesalazine

How does it work?

No one knows exactly how mesalazine works. It is thought to act on the inflamed lining of the gut (intestine) by stopping the body producing chemicals that cause inflammation.

Mesalazine helps by reducing the redness and swelling (inflammation) in your intestine. This improves your symptoms.

Mesalazine has a similar effect to immunosuppressants. It can reduce the numbers of white cells in your blood, reducing your body's ability to fight infection.

How long does it take to work?

Mesalazine does not work straight away.

Depending on how bad your symptoms are, it may take from a few hours to a few weeks for them to start improving.

It may take up to a few months for your symptoms to be completely treated if they are severe.

How long will I take it for?

Mesalazine can be used at a higher dose for a short time to treat flare-ups.

You can also take it long term to keep inflammation under control and prevent symptoms from flaring up again. How long you use it for will depend on how bad your condition is.

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

Why is it important to stick to the same brand?

Different brands and forms of mesalazine (tablets, granules, rectal foam, suppositories and enemas) work on different parts of your gut. Your doctor will prescribe the brand that releases mesalazine in the part of your gut that needs it most.

You will usually stay on the same brand and type of mesalazine if it's working to control your symptoms. However, if it does not help your symptoms, your doctor may try you on a different one.

Always use the brand that your doctor has prescribed for you. It's important to make sure the pharmacist gives you the right brand when you collect your prescription.

Is it safe to take for a long time?

Mesalazine can be taken long term. However your doctor will want to check how your kidneys are working during treatment. In rare cases mesalazine can cause kidney problems.

These checks usually happen once every 3 months for the first year. They will usually be once a year after that or as often as your doctor recommends.

Can I stop taking mesalazine?

If you are thinking of stopping mesalazine, discuss this with your doctor first as your symptoms may come back.

If side effects are bothering you and you're thinking of stopping your mesalazine, talk to your doctor first. They may want to review your treatment.

Do not stop taking or using mesalazine unless your doctor tells you to.

Can I take mesalazine before surgery?

Tell the specialists who are going to carry out your surgery that you are taking mesalazine. They will tell you if you need to stop taking it.

Can I take painkillers with mesalazine?

You can take paracetamol with mesalazine.

However, it's best to avoid non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen.

Like mesalazine, NSAIDs can cause problems with the way your kidneys work. They can also irritate the gut and so increase the risk of ulceration and bleeding.

Ask a pharmacist or doctor for advice if paracetamol is not working for you.

Can I drink alcohol with it?

You can drink alcohol while taking mesalazine. However, alcohol can irritate your gut so may make symptoms worse.

It's best to stick to the national guidelines of no more than 14 units a week. A standard glass of wine (175ml) is 2 units. A pint of lager or beer is usually 2 to 3 units of alcohol.

Is there any food or drink I need to avoid?

You can usually eat and drink normally while taking or using mesalazine. If you have indigestion or feel sick, it's best to stick to simple meals, and avoid alcohol and spicy foods.

For inflammatory bowel disease, your doctor may advise you to make some changes to your diet as part of your treatment. This can include following a special diet or adding a nutritional supplement.

Will it affect my fertility?

There's no clear evidence to suggest that taking mesalazine will reduce fertility in either men or women.

Speak to your doctor if you're trying to get pregnant. They may want to review your treatment.

Will it affect my contraception?

Mesalazine does not affect any type of contraception, including the combined pill and emergency contraception.

However, if taking or using mesalazine makes you vomit or have severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy. Look on the pill packet to find out what to do.

Read more about what to do if you're taking the pill and you're being sick or have diarrhoea.

Can I drive or ride a bike?

Mesalazine is unlikely to affect your ability to drive, ride a bike or operate tools and machinery.

Are there other treatments for Crohn's disease and ulcerative colitis?

Other medicines used to treat Crohn's disease and ulcerative colitis include:

Read more about the different treatments for Crohn's disease.

Read more about the different treatments for ulcerative colitis.

Page last reviewed: 19 July 2021
Next review due: 19 July 2024