Med of the Month: Azathioprine

This Women's History Month, we're highlighting one of the inventions by the late Dr. Gertrude B. Elion.

Born in New York City in 1918, Dr. Elion’s path into science was shaped early by curiosity and personal loss. After her beloved grandfather died of cancer when she was fifteen, she became determined to pursue work that could one day help treat serious disease. Despite graduating with top academic honors, opportunities in laboratory research were scarce, particularly for women during the Great Depression. Undeterred, she continued studying while teaching science in New York City schools and completing graduate research at night and on weekends, ultimately earning her master’s degree in chemistry from New York University in 1941.

Her career would later transform modern drug development. Working alongside Dr. George H. Hitchings, Elion helped pioneer a targeted, mechanism-based approach to medicine that moved pharmaceutical research beyond trial and error. Their work ultimately earned Elion a share of the 1988 Nobel Prize in Physiology or Medicine, recognizing discoveries that led to treatments for cancer, transplantation, infectious diseases, and autoimmune conditions.

Among those contributions was azathioprine, a medication that continues to play an important role in immunosuppressive therapy today. Azathioprine is a prodrug, meaning it doesn't become active until the body converts it. In this case, into 6-mercaptopurine (6-MP), which is itself another one of Dr. Elion's discoveries. Once active, it interferes with DNA synthesis and slams the brakes on rapidly dividing immune cells.

For dentists, this matters because patients on azathioprine come to your chair with a very different immune landscape than your typical patient.

Generic Name: Azathioprine

Brand Name(s): Azasan, Imuran

Pronunciation: ay za THYE oh preen

About this drug:

• Azathioprine is an immunosuppressant used to relieve joint pain and swelling for patients with rheumatoid arthritis.

• It is also used to prevent the body from rejecting a kidney after a transplant.

Dentistry-related tidbits:

• If treating a patient taking azathioprine, note that:

  • Azathioprine may cause thrombocytopenia.

  • Azathioprine may increase a patient's chance of getting a serious infection. Advise the patient to avoid being around sick people and wash their hands frequently. Follow any dental infections closely.

Staying Safe: important interactions to be aware of

• Using a tool like MedAssent DDS Rx Check can help support safe prescribing. Important interactions include:

  • Steroids in combination with azathioprine may increase the risk of serious infections (only prescribe if absolutely necessary and for the shortest duration of therapy).

  • Linezolid and trimethoprim can increase the risk of myelosuppression in patients taking azathioprine.

Fun facts:

• Dr. Elion earned a Nobel Prize without ever completing a PhD. While working full-time in pharmaceutical research, Dr. Elion pursued doctoral studies at night. After several years, she was told she would need to leave her job to continue the program full-time. Faced with that decision, she chose to remain in the laboratory instead. Years later, after receiving multiple honorary doctorates and the Nobel Prize, she reflected that staying in research had been the right choice.

• Azathioprine was born from cancer research, not transplant medicine. Dr. Gertrude B. Elion and Dr. George Hitchings were originally studying how rapidly dividing cells make DNA in order to develop treatments for leukemia. Their work led to the creation of 6-mercaptopurine, a drug that interfered with cell replication. Researchers later realized that modifying this compound could selectively suppress immune activity, leading to the development of azathioprine. What began as cancer drug research ultimately became one of the first medications capable of preventing organ transplant rejection, helping make modern transplantation possible.

• Paradoxically, azathioprine may be used off-label to treat immune thrombocytopenia (ITP). Azathioprine is a purine analog immunosuppressant that works by inhibiting lymphocyte proliferation. In ITP, the core problem is an overactive immune system destroying platelets. Azathioprine addresses this by (1) suppressing autoreactive B and T lymphocytes that are driving the antiplatelet antibody production, (2) reducing overall immune activation. This can lead to fewer antibodies, less platelet destruction, and a rising platelet count. The drug-induced thrombocytopenia from azathioprine is a different mechanism: primarily through bone marrow suppression (myelosuppression), where it reduces platelet production rather than destruction. This is a dose-dependent, toxic effect.

Get more dental-specific drug information with the Digital Drug Handbook (web) or BrushUp Rx (mobile app).