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Your doctor may suggest you try drugs that curb your immune system after you've already had other treatments for Crohn's disease. These drugs can play a key role in keeping flare-ups away.

How They Work

Drugs that target your immune system help reduce inflammation in your gut, which is a cause of your Crohn's symptoms.

The inflammation is a result of a complicated set of events in your body. Taking drugs that curb the immune system, as well as other drugs like steroids and antibiotics, can break the process that leads to inflammation. This will ease your symptoms and keep flare-ups away.

When to Use Drugs That Target the Immune System

There are several situations in which your doctor might turn to these drugs to treat your Crohn's:

Steroids Aren't Working. Sometimes you get immune system drugs after you've already been treated with steroids. Your doctor might turn to them if the steroids aren't effective or are only partly effective. Or there might be a concern that you're becoming too dependent on steroids to reduce inflammation.

Keep Flares Away. Immune system drugs can help keep your Crohn's symptoms from coming back. But it may take up to 3 months before they take effect.

Treat a Fistula. A fistula is a sore that forms a tunnel that goes from one part of your intestine to another. The tunnel may also go from your digestive system to nearby areas such as the bladder, vagina, anus or skin.

Sometimes doctors combine immune system drugs with corticosteroids during flare-ups of disease. This may speed up treatment and curb side effects.


One type of drug that targets your immune system drug is called an "immunomodulator." These drugs work by curbing the immune system throughout the body, not just the gut.

Some common types of immunomodulators are:

  • Azathioprine
  • Methotrexate
  • Mercaptopurine

Azathioprine and mercaptopurine may be used to keep flare-ups away. But either can take months to start working. You may also need a faster-acting drug such as a corticosteroid.

Side effects of azathioprine and mercaptopurine include nausea, vomiting, and less resistance to infection.

Side effects of methotrexate include:

  • Nausea and diarrhea
  • Fatigue
  • Scarring of the liver if used long-term

A less common approach for using immunomodulators, but one that's under study, is known as "top down therapy." In this method, you'll get treated aggressively with immunomodulators to get rid of symptoms. Once that's achieved, you'll switch to other types of drugs, like 5-ASAs and antibiotics, for long-term treatment.

You and your doctor can discuss which approach makes sense for you.