Mesalazine (rectal)

Sounds like 'me-SAL-a-zeen'

Easy-to-read medicine information about mesalazine (rectal) – what it is, how to use mesalazine safely and possible side effects. Mesalazine is commonly called Asacol or Pentasa.

Type of medicine Also called
  • Belongs to a group of medicines called aminosalicylates
  • Asacol suppository®
  • Asamax 500 suppository®
  • Pentasa enema®
  • Pentasa suppository®

What is mesalazine?

  • Mesalazine suppositories or enema are used to treat bowel conditions such as ulcerative colitis.
  • It works by reducing inflammation, and may decrease symptoms such as pain and diarrhoea. The suppositories or enema are inserted into the rectum (bottom) and deliver the mesalazine directly into the lower bowel (lower colon or rectum).  
  • Mesalazine can also be given by mouth, as tablets or granules. For more information on mesalazine tablets and granules see mesalazine (oral).


  • The usual dose of the suppositories or enema is 1 to 2 grams daily.
  • Always take your mesalazine exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much mesalazine to take, how often to take it, and any special instructions.

How to use mesalazine suppositories

  • Use mesalazine suppositories at the same times each day.
  • It is best to have a bowel motion (poo) before using mesalazine suppositories. If you have a bowel motion soon after using the suppositories, you may lose the medication.
  • Avoid using mesalazine suppositories just before having a bath, shower or going swimming.
  • It is important to put them in correctly. Your doctor, pharmacist, or nurse will explain how to use your mesalazine suppositories. As a guide:
    • Wash your hands. Remove the wrapper or foil around the suppository. Lie on your side, with your knees up. Put the suppository as far as possible into the rectum. Stay lying down for a few minutes, so the suppository dissolves.  
  • If you forget a dose, just take the next dose at the right time. Do not take double the dose.

How to use mesalazine enema

  • Use the mesalazine enema at night.
  • It is best to have a bowel motion (poo) first. If you have a bowel motion soon after, you may lose the medication.
  • It is important to use it correctly. Your doctor, pharmacist, or nurse will explain how to use it. As a guide:
    • Remove the foil packet. If it feels cold, put the enema in warm water for a few minutes. Shake the enema just before using, to mix it up. To open, twist the top around (360°). You can put water soluble lubricating jelly on the tip. Lie on your left side with your left leg out straight and right leg bent forward for balance. Carefully put the tip of the enema into the rectum and squeeze to empty slowly over 30 to 40 seconds. When it is empty take it out. Stay on your side for 5 to 10 minutes or you can stay in bed until the next morning.
  • When ulcerative colitis is active, it may be difficult to keep the full enema contents in. 
    • Your doctor may say to use some of it 2 to 3 times a day. If you do this, keep the unused part in the foil pack, away from light and throw away any left over at the end of the day.

Possible side effects

Like all medicines, mesalazine can cause side effects, but not everyone gets them. Often side effects improve as your body gets used to the new medicine. You will need to have blood tests to make sure it is not affecting your blood or kidneys.

Side effects What should I do?
  • Tummy pain
  • Feeling nauseous (sick) or being sick (vomiting)
  • Gas or wind in the tummy or feeling bloated
  • Diarrhoea (runny poo)
  • These are quite common when you first start mesalazine, and usually go away with time
  • Tell your doctor if troublesome
  • Signs of problems with your liver such as severe tummy pain, yellowing of the eyes and skin, dark urine.
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Signs of problems with your blood cells such as bruising or bleeding easily, ongoing sore throat, mouth ulcers, dizziness and feeling tired and fever.
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Signs of an allergic reaction such as skin rash, itching, blisters, peeling skin, swelling of the face, lips, mouth or have problems breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116

Learn more

Medsafe Consumer Information Sheets:

Asacol suppositories® 
Asamax 500 suppositories® 
Pentasa suppositories  
Pentasa enema®

Credits: Sandra Ponen, Pharmacist. Last reviewed: 24 Mar 2016