Chemotherapy involves treating an illness using chemicals. It has long been successful in treating people with cancer. Certain forms of chemotherapy are also effective for autoimmune disorders like Crohn’s disease.

When used for Crohn’s, chemotherapy medications are sometimes called immunomodulators. That’s because they alter the body’s immune system to decrease inflammation and other symptoms.

For people with Crohn’s disease, these medications can help get them off steroids and keep them in remission.

Methotrexate is another popular Crohn’s treatment. It was originally used for treating breast cancer. Methotrexate is also used as chemotherapy for lymphoma and leukemia. The dosage is significantly lower for treating autoimmune disorders.

Methotrexate is given once a week by injection. It blocks cell production, which makes it effective in controlling inflammation caused by Crohn’s disease. Methotrexate’s side effects include a reduction in blood cells produced by bone marrow.

This can lead to complications. People taking methotrexate are usually tested regularly to ensure adequate blood counts.

People taking methotrexate will often receive blood tests every two months. These tests check liver and kidney function. Lung scarring is also possible. People may be asked to watch for issues like persistent coughing or trouble breathing. Common side effects include:

  • headache
  • nausea
  • vomiting
  • fatigue

Individuals using methotrexate often have to take a daily dose of folic acid. This helps to counter some of the drug’s side effects.

Methotrexate shouldn’t be used by pregnant women with Crohn’s disease. The drug can cause birth defects or even death in a developing baby.

Mercaptopurine, also known as 6-MP, comes in tablet form. It’s one of the more popular chemotherapy treatments for Crohn’s. Classified as an antimetabolite, 6-MP interferes with metabolic action. Antimetabolites have been effective in treating Crohn’s.

The side effects of 6-MP can be challenging to manage, though. Serious side effects include a temporary reduction in white and red blood cell counts. This can increase your risk of infection and anemia.

Liver and pancreas problems and traditional chemotherapy side effects like nausea and vomiting may occur.

Infliximab is a TNF (tumor necrosis factor) blocker. It’s used to treat moderate to severe Crohn’s disease. It was initially designed as a chemotherapy drug to treat cancer but wasn't effective for cancer.

The drug has been shown to work against autoimmune diseases like rheumatoid arthritis and Crohn’s. These types of medicines are now known as a biologics because they work by blocking certain proteins created by the immune system.

Infliximab is administered via an intravenous line (IV) in a medical facility. The process usually takes several hours. It carries a lymphoma cancer risk, mostly for young people. It also comes with a risk of tuberculosis and fungal infections.

These conditions have sometimes been fatal in people with Crohn’s.

Some people have experienced allergic reactions to infliximab. A few people have also reported lupus-like symptoms, including:

  • chest or joint pains
  • shortness of breath
  • rashes

If you begin to experience these side effects, your doctor may choose to change your dosage or take you off the drug.

Infliximab shouldn’t be used by people with certain heart problems, because it can make these conditions worse. Talk to your doctor before starting infliximab if you have heart problems.