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Olsalazine for ulcerative colitis

Take olsalazine tablets or capsules with a meal or after a snack.

It is important that you keep your regular appointments with your doctor so that your progress can be checked. You will need to have regular blood tests.

Common side-effects tend to be minor, but on occasions, olsalazine can cause more serious problems. You should tell your doctor immediately if you have any unexplained bleeding, bruising, red or purple discolorations of your skin, a sore throat, a high temperature (fever) or you feel generally unwell.

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About olsalazine

Type of medicine


Used for

Ulcerative colitis in adults and in children aged over 12 years

Available as

Capsules and tablets

Ulcerative colitis causes inflammation of the large intestine. This can lead to damage to the lining of your intestine (ulceration) and bleeding, and causes symptoms of tummy (abdominal) pain and diarrhoea.

Although it is not clear exactly how olsalazine works, it is thought to act on the cells which line your intestine to change the way they make and release certain chemicals. These chemicals are thought to be a factor in causing the symptoms of ulcerative colitis. Olsalazine allows the damaged areas of your intestine to recover, and then helps to prevent your symptoms from flaring up again.

Before taking olsalazine

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking olsalazine it is important that your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breastfeeding.

  • If you have any problems with the way your kidneys work.

  • If you have asthma and/or experience severe allergies.

  • If you have ever had an allergic reaction to a medicine. It is particularly important that you tell your doctor if you have had an unusual reaction to aspirin or to any other salicylate medicine.

  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

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How to take olsalazine

  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The manufacturer's leaflet will give you more information about olsalazine and a full list of side-effects which you may experience from taking it.

  • Take olsalazine exactly as your doctor tells you to. He or she will tell you how many tablets/capsules to take for each dose, and when to take them.

  • Your dose may be increased over the first few weeks to make sure that you are taking a dose that best controls your symptoms.

  • Your dose may be reduced again once your symptoms have improved.

  • It is likely that you will be asked to take olsalazine twice each day, usually morning and evening. Some people may be asked to take it three times each day for a short while. The directions will be printed on the label of your pack to remind you.

  • Take olsalazine tablets or capsules with a drink of water during a meal, or straightaway after a meal. Taking olsalazine with or after food will help to keep side-effects, like diarrhoea, to a minimum.

  • If you forget to take a dose, take it as soon as you remember unless your next dose is due. If when you remember it is nearly time for your next dose, then leave out the forgotten dose but remember to take your next dose when it is due. Do not take two doses together to make up for a missed dose.

Getting the most from your treatment

  • Try to keep your regular appointments with your doctor and clinic. This is so your doctor can check on your progress. Your doctor will want you to have regular blood tests during this treatment.

  • Treatment with olsalazine may be long-term in order to prevent your symptoms from flaring up from time to time. Continue to take it unless you are advised otherwise by your doctor.

  • Your doctor may advise you make some changes to your diet as part of your treatment. This may include a special diet or a nutritional supplement.

  • If you have an allergic condition, such as asthma, you should let your doctor know straightaway if you find your allergic symptoms get worse. If this happens, your doctor may want to review your treatment or will arrange to see you more often to keep an eye on your progress.

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Can olsalazine cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with olsalazine. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common olsalazine side-effects - these affect fewer than 1 in 10 people who take this medicine

What can I do if I experience this?


Drink plenty of water to replace lost fluids. Make sure you take olsalazine after meals

Feeling sick (nausea) or being sick (vomiting), indigestion, tummy (abdominal) pain

Stick to simple foods - avoid rich or spicy meals

Headache, joint or muscle pain

Drink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the pain continues, speak with your doctor

Important: olsalazine can sometimes cause allergic reactions or problems with your blood cells. You should contact your doctor immediately if:

  • You have any difficulty in breathing, or any swelling of your face or tongue.

  • You have any unexplained bleeding, bruising, red or purple discolorations on your skin, a sore throat, a high temperature (fever), or if you feel generally unwell during this treatment.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

How to store olsalazine

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

If you buy any medicines check with a pharmacist that they are safe to take with your other medicines.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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