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FAQ: Azathioprine

Why is this medication being recommended?

Azathioprine is part of a class of drugs called immunosuppressants. It suppresses the body's immune response and reduces inflammation in your lungs. Because inflammation is the precursor to fibrosis (scarring), we hope azathioprine will prevent the formation of lung fibrosis and allow the inflamed lung to return to normal.

What special precautions should I follow?

Before taking azathioprine:

  • Tell your doctor and pharmacist if you are allergic to azathioprine or any other medications.

  • Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements and herbal products you are taking. Be sure to mention those listed in the important warning section of the medication insert, as well as any of the following:
    • Aallopurinol (Zyloprim)
    • Angiotensin-converting enzyme (ACE) inhibitors such as benazepril (Lotensin), captopril (Capoten), enalapril (Lexxel, Vasotec), fosinopril (Monopril), lisinopril (Prinivil, Zestril), moexipril (Univasc), perindopril (Aceon), quinapril (Accupril), ramipril (Altace) and trandolapril (Mavik, Tarka)
    • Anticoagulants or 'blood thinners' such as warfarin (Coumadin)
    • Antimalarials such as chloroquine (Aralen), hydroxychloroquine (Plaquenil), mefloquine (Lariam), primaquine, proguanil (Malarone), pyrimethamine (Daraprim) and quinine
    • Cancer chemotherapy medications
    • Co-trimoxazole (Bactrim, Septra, Sulfatrim)
    • Cyclosporine (Neoral, Sandimmune)
    • Gold compounds such as auranofin (Ridaura) and aurothioglucose (Aurolate, Solganal)
    • Methotrexate (Rheumatrex)
    • Penicillamine (Cuprimine, Depen)
    • Sirolimus (Rapamune)
    • Tacrolimus (Prograf)

  • Tell your doctor if you have any type of infection or if you have, or have ever had, kidney, liver or pancreas disease.

  • Tell your doctor if you are pregnant, plan to become pregnant or are breast-feeding. Use birth control to be sure you or your partner will not become pregnant while you are taking this medication. Do not breast-feed while taking this medication.

  • If you are having surgery, including dental surgery, tell the doctor or dentist that you are taking azathioprine.

  • You should know that azathioprine may decrease your ability to fight infection. Stay away from people who are sick, wash your hands often and watch for signs of infection and fever.

What side effects can this medication cause?

Azathioprine may cause side effects. Tell your doctor if any of the following symptoms are severe or do not go away:

  • Diarrhea
  • Muscle aches
  • Upset stomach
  • Vomiting

Some side effects can be serious. The following symptoms are uncommon, but if you experience any of them, or any symptoms listed in the important warning section of the medication insert, call your doctor immediately.

  • Blurred vision
  • Cough
  • Flu-like symptoms
  • Lack of energy
  • Loss of appetite
  • Mouth sores
  • Pain in the upper right part of the stomach
  • Rash
  • Stomach pain
  • Yellowing of the skin or eyes

What monitoring will I need?

Your doctor will order regular lab tests to check your response to azathioprine and monitor for toxicity. You will need to have your blood counts — white blood cells, red blood cells and platelets — and liver enzymes checked regularly. Your doctor may order additional tests depending on the results.

For additional information on azathioprine, please visit


Reviewed by health care specialists at UCSF Medical Center.

This information is for educational purposes only and is not intended to replace the advice of your doctor or health care provider. We encourage you to discuss with your doctor any questions or concerns you may have.