What is sulfasalazine?

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

Sulfasalazine reduces inflammation, pain and swelling in your joints and may reduce the progression of your condition.

It can be used to treat:

Sulfasalazine won’t start to work immediately. It could be at least 1- 3 months before you notice that your symptoms are getting better.

Who can take sulfasalazine?

Sulfasalazine can be taken by adults and by children aged two years and older.

You may have received other drugs first, or sulfasalazine may be the first DMARD you are given.

You won't be given sulfasalazine if you:

  • are allergic to any of the ingredients of sulfasalazine
  • are allergic to salicylates – a natural chemical that is found in some foods and aspirin
  • are allergic to antibiotics known as sulfonamides
  • have significant problems with your kidneys or liver
  • have a disease known as porphyria – a rare blood pigment disorder
  • if you have G6PD (glucose-6-phosphate dehydrogenase) deficiency – a condition where your red blood cells break down when exposed to certain foods, drugs, infections or stress.

Before you’re given sulfasalazine, you will have blood tests (checking for anaemia, white cell count, and liver and kidney function).

You will also continue to have these tests whilst taking the treatment. Your doctor will advise on the frequency of tests but, in general, you’re likely to need blood tests monthly for the first 6 months, then about every 6 months after that.

How is it taken?

You will probably be given sulfasalazine as a tablet, which you should swallow whole with a glass of water. Do not break, crush or chew them.

You can take sulfasalazine with or without food. But try to space your doses evenly throughout the day.

Your doctor will tell you the correct dose to take. You’ll usually start on a low dose, which is slowly increased each week. Follow your doctor's advice carefully. The usual dose is two tablets (500 mg each) twice a day but this can vary, depending on the reason you are taking sulfasalazine and how well it works for you.

If you miss a dose of sulfasalazine, take it as soon as you remember – unless it's nearly time for your next dose. In this case, skip the missed dose and take your next one at the usual time. Do not take a double dose to make up for a forgotten dose.

You can also get sulfasalazine as a liquid or as a suppository, a medicine you place in your bottom. Tablets are the preferred option but you can talk to your doctor about these alternatives if you have trouble taking tablets.

Because it’s a long-term treatment, it is important to keep taking sulfasalazine:

  • even if it does not seem to be working at first
  • even when your symptoms start to improve, to help control your condition.

Possible risks and side effects

The most common side effects of sulfasalazine are:

  • feeling or being sick
  • heartburn
  • diarrhoea
  • stomach pain
  • dizziness
  • difficulty sleeping
  • cough
  • joint pain
  • fever
  • headaches
  • rashes.

Sulfasalazine may cause your urine to change colour, to orange, but this is nothing to worry about. It may also stain tears and soft contact lenses yellow.

Sulfasalazine is not thought to increase risk of infection, unless it causes the rare side effect of low white blood cells.

These side effects usually happen during the first three months of treatment. But they often stop if your dose is lowered.

If the side effects of sulfasalazine improve and it’s helping your symptoms, you may be able to increase your dose again after a while. However, you will need to stop this medication if you experience severe side effects.

Serious side effects are very rare. But you should be aware of them.

Call your doctors straight away if you have:

  • any signs of an infection – including a high temperature, sore throat, fever, ear or sinus pain, a cough, pain when peeing, a cut that won’t heal or if you generally feel ill

  • a severe skin rash that causes blistering (which can affect the mouth and tongue too). This can be a sign of Stevens–Johnson Syndrome or toxic epidermal necrolysis (TEN). This is very rare.

  • a high temperature, sore throat, pale skin, unusual bruising or bleeding or unusual tiredness or weakness. These can be signs of a blood problem.

  • change in the amount of pee you produce or pain when peeing. These can be signs of kidney problems.

  • chest pain, an increase in heartbeat or feeling much more tired than usual. These can be signs of heart problems.

Tips to reduce your risk of infection

  • Try to avoid close contact with people you know have an infection.
  • Wash your hands regularly and carry around a small bottle of antibacterial hand gel.
  • Keep your mouth clean by brushing your teeth regularly.
  • Stop smoking if you’re a smoker.
  • Make sure your food is stored and prepared properly.
  • Try to keep your house clean and hygienic, especially the kitchen, bathrooms and toilets.

Effects on other treatments

Check with your doctor before starting any new medication. Remember to mention that you are on sulfasalazine if you are being treated by anyone other than your usual healthcare team.

It's very common to use methotrexate alongside sulfasalazine – this combination can be very helpful in managing your condition without increasing side effects.

Some drugs may interact with sulfasalazine. Tell your doctor or pharmacist if you’re taking: 

  • any medicine for high blood sugar or diabetes, such as metformin or glibenclamide
  • methenamine, an antibiotic for treating urinary tract infections
  • digoxin, used to treat heart failure
  • folic acid
  • azathioprine and mercaptopurine – drugs used to help to suppress your body’s immune response in organ transplantation and certain chronic inflammations such as rheumatoid arthritis.

Don’t use complementary treatments, such as herbal remedies, without discussing this first with your doctor or pharmacist as some of them could react with sulfasalazine.

You can carry on taking painkillers if needed, unless your doctor says otherwise.


It's usually fine for people on sulfasalazine to have vaccinations, but check with your GP and rheumatology team beforehand to make sure a vaccine is safe.

It’s recommended that you have the vaccination against COVID-19. It’s also recommended that you have the pneumonia vaccine and yearly flu vaccine injection while taking sulfasalazine.

Having an operation

If you're due to have any surgery or dental treatment, tell your doctor or dentist that you are taking sulfasalazine beforehand.

You’ll usually be able to carry on taking sulfasalazine. But in some cases, it will need to be stopped for a while before your operation.


There’s no need to avoid alcohol while taking sulfasalazine.

However, guidelines state that adults shouldn't have more than 14 units a week, and that they should spread them out over the course of the week. In some circumstances your doctor may advise lower limits.

You can find out more about units of alcohol at

Fertility, pregnancy and breastfeeding

Guidelines say that it's generally safe for women to take sulfasalazine when trying for a baby and during pregnancy. It's often recommended that you continue sulfasalazine throughout pregnancy to prevent flare-ups.

If you’re pregnant and taking sulfasalazine, you should also take folic acid tablets. This is because sulfasalazine can reduce your levels of folic acid. Folic acid reduces the risk of having a baby born with defects of the brain, spine or spinal cord, such as spina bifida. You can get folic acid tablets from a supermarket or pharmacist.

You may be able to take sulfasalazine while breastfeeding, unless the baby is premature or at risk of jaundice. If you are worried, speak to your rheumatology team.

Current guidelines say that you don’t have to stop taking sulfasalazine before trying to father a child.

Sulfasalazine can reduce your sperm count. But this usually improves 2–3 months after you stop treatment. It shouldn’t be used as a form of contraception though. If you’ve been trying for a baby for a year or more while on sulfasalazine, you should discuss this with your doctor and arrange to see a fertility specialist to check sperm count and rule out other issues.