What is sulfasalazine?

Sulfasalazine is a type of drug known as a disease-modifying anti-rheumatic drug (DMARD).

It works by modifying the underlying disease process to reduce inflammation, pain and swelling in your joints. It may be prescribed by your GP or a rheumatologist to treat:

Sulfasalazine doesn't work immediately. It may be at least 12 weeks before you notice the benefits.

Are there any reasons I won't be prescribed sulfasalazine?

You shouldn't take sulfasalazine if you're known to have an allergy to salicylates (e.g. aspirin) or to sulphonamides (a type of antibiotic).

How do I take it?

Sulfasalazine is generally prescribed as Salazopyrin EN-Tabs. These tablets are specially coated so that they don't dissolve quickly in your stomach.

Sulfasalazine tablets should be taken with a glass of water and should be swallowed whole, not crushed or chewed.

Your doctor will advise you on the correct dose. Usually you’ll start on a low dose, e.g. one 500 mg tablet daily. This is usually increased gradually over a period of about four weeks – typically to two 500 mg tablets taken twice daily. The dose may be adjusted according to the severity of your symptoms.

How long does it take to work?

Sulfasalazine doesn’t work immediately. It may be at least 12 weeks before you notice the benefit. Because it's a long-term treatment, it's important to keep taking sulfasalazine (unless you have severe side-effects):

  • even if it doesn't seem to be working at first
  • even when your symptoms improve (to help keep the disease under control).

Side-effects and risks

The most common side-effects of sulfasalazine are nausea (feeling sick), diarrhoea, stomach pain, dizziness, headache and skin rashes. These side-effects usually occur during the first three months of treatment and often clear up if the dose is reduced. You may be able to increase the dose again after a time if your tolerance improves and if the sulfasalazine is helping your symptoms.

Taking sulfasalazine can affect your blood count or your liver, but these effects can be picked up at an early stage by regular blood tests. You may be asked to keep a record of your blood test results in a booklet and to take this with you when you visit your GP or the hospital.

You must not take sulfasalazine unless you're having regular blood tests.

You should tell your doctor or rheumatology nurse straight away if you develop any of the following after starting sulfasalazine:

  • a sore throat, fever or any other symptom of infection
  • unexplained bruising
  • any other new symptoms or anything else that concerns you.

Your urine may change colour (to orange) with sulfasalazine but this is nothing to worry about. Sulfasalazine may also stain your tears and soft contact lenses yellow.

Effects on other treatments

Check with your doctor before starting any new medications and remember to mention you're on sulfasalazine if you're treated by anyone other than your usual healthcare team.


You can have vaccinations while on sulfasalazine.


There's no particular reason to avoid alcohol while you're on sulfasalazine.

Fertility, pregnancy and breastfeeding

We suggest you speak to your doctor as soon as possible if you're planning a family, if you become pregnant or if you're thinking of breastfeeding.

However, guidelines state that it's safe for women to continue using sulfasalazine when trying for a baby and during pregnancy. It's often recommended that you continue sulfasalazine throughout pregnancy to prevent a flare-up of your condition. You should also take folic acid tablets (5 mg daily) as sulfasalazine can reduce levels of folic acid in the body.

Sulfasalazine can cause a fall in sperm count, leading to a temporary decrease in male fertility but must not be relied upon for contraception. The effect on sperm count is reversed if treatment is stopped, and research hasn't shown this to be a problem. You should discuss this with your rheumatologist, but current guidelines advise that it's not necessary for men to stop sulfasalazine before trying to father a baby. However, if you're on sulfasalazine and you've been trying for a baby for a year or more, you should discuss this with your doctor and arrange to see a fertility specialist to rule out other problems.

Sulfasalazine is considered safe to use if you're breastfeeding unless your baby is premature or at risk of jaundice. Speak to your rheumatology team if you're concerned about this.