Sounds like 'ohl-SAL-uh-zeen'

Olsalazine is used to treat ulcerative colitis. Find out how to take it safely and the possible side effects. Olsalazine is also called Dipentum.

What is olsalazine?

Olsalazine is used to treat ulcerative colitis. It works by reducing inflammation in the gut and may lessen symptoms of pain and diarrhoea (runny poo). Olsalazine allows the gut to heal and helps to prevent symptoms from flaring up. Read more about ulcerative colitis.

Supply issue olsalazine 250 mg capsule (Dipentum)
From February 2021 olsalazine 250mg capsules (Dipentum) will be out of stock long term. This has also affected supplies of the 500mg tablet. Learn more about olsalazine supply issue.  


In Aotearoa New Zealand olsalazine comes as tablets (500mg). 

  • Your doctor will start you on a low dose and increase it over a few days to make sure that you're taking a dose that best controls your symptoms. Your dose may be reduced again once your symptoms have improved.
  • The usual dose of olsalazine is 500mg twice a day after meals. 
  • Always take olsalazine exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much olsalazine to take, how often to take it and any special instructions.

How to take olsalazine

  • Take olsalazine tablets with a glass of water. Take your dose with or soon after food to reduce side-effects, such as diarrhoea (runny poo) and stomach upset.
  • Take your olsalazine dose at the same times each day, usually in the morning and the evening. 
  • If you forget to take your dose, take it as soon as you remember that day. But if it is nearly time for your next dose, just take the next dose at the right time. Don't take double the dose.
  • Olsalazine will start working straight away but it may take a week or so for your symptoms to improve. 

Things to consider while you are taking olsalazine

You'll need regular blood tests while taking olsalazine to make sure it's not causing problems with your liver, kidneys or blood.

Olsalazine may interact with other medicines. Tell your doctor or pharmacist about all medicines you are taking including over-the-counter medicines, herbal and complementary medicines and recreational drugs. 

Let your doctor know if you are pregnant or breastfeeding.

What are the side effects of olsalazine?

Like all medicines, olsalazine can cause side effects, but not everyone gets them. Often side effects improve as your body gets used to the new medicine. 

Side effects What should I do?
  • Diarrhoea (runny poos)
  • Tummy pain
  • Feeling sick (nausea) or being sick (vomiting)
  • These are quite common when you first start taking olsalazine, and usually go away with time.
  • Take your olsalazine with food. 
  • Tell your doctor if they bother you.
  • Headache
  • Tell your doctor if this bothers you.
  • Signs of problems with your blood cells such as bruising or bleeding easily, ongoing sore throat, mouth ulcers, dizziness, feeling tired, fever or chills.
  • 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 you have problems breathing
  • Tell your doctor immediately or ring Healthline 0800 611 116.
  • Signs of problems with your liver, such as yellowing of your skin or eyes, dark urine (pee) or pain in your abdomen (tummy/puku)
  • Tell your doctor immediately or ring Healthline 0800 611 116.
For more information on side effects, see the Medsafe consumer information leaflet Dipentum

Did you know that you can report a medicine side effect to the Centre for Adverse Reactions Monitoring (CARM)? Report a side effect to a product

Learn more

The following links have more information on olsalazine.

Olsalazine NZ Formulary
 Medsafe Consumer Information Sheet (NZ)


Olsalazine sodium NZ Formulary
Dipentum® Medsafe, NZ

Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 10 Jan 2023