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.

Type of medicine

Also called

  • It belongs to a group of medicines called aminosalicylates

  • 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). It allows the damaged gut to heal and helps to prevent symptoms from flaring up again. Read more about ulcerative colitis.


  • In Aotearoa New Zealand olsalazine is available as 500 mg tablets.
  • The usual dose of olsalazine is 500 mg twice a day. 
  • Your doctor will start you on a low dose and will increase it over the first few days depending on how well you tolerate it. You will be given higher doses during ‘flare-ups’, and your dose will be reduced again when your symptoms improve.
  • Always take your 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 your olsalazine with a full glass of water. Taking olsalazine with or soon after food helps to reduce side-effects, such as diarrhoea (runny poo) and stomach upset.
  • Timing: Take your olsalazine dose at the same times each day, usually in the morning and the evening. 
  • Missed dose: 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. Do not take double the dose.
  • Olsalazine will start working straight away but it may take a week or so for your symptoms to improve. 

Precautions before starting olsalazine

  • Do you have asthma?
  • Do you have any problems with your kidneys or liver?
  • Do you have a bleeding disorder?
  • Are you taking any other medicines such as warfarin?
  • Are you taking any over-the-counter and complementary medicines, eg, vitamins, minerals, herbal or naturopathic medicines?

If you have answered yes to any of these questions, it’s important that you tell your doctor or pharmacist before you take olsalazine. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Precautions while taking olsalazine

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

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.
  • Signs of problems with your blood cells such as bruising or bleeding easily, ongoing sore throat, mouth ulcers, dizziness,  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.
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

Additional resources for healthcare professionals

Olsalazine 250 mg capsule (Dipentum): Out of stock long term Pharmac, NZ.


Credits: Sandra Ponen, Pharmacist. Reviewed By: Maya Patel, MPharm PGDipClinPharm, Auckland Last reviewed: 26 Jan 2022