Therapeutic drug monitoring (TDM) of thiopurine drugs


Thiopurine drugs are prescribed to treat patients with acute lymphoblastic leukemia, autoimmune diseases and inflammatory bowel disease. Thiopurine drugs must be metabolized to pharmacologically active metabolites in order to exert its effects. The amount of active metabolites is regulated by the enzyme, thiopurine methyltransferase, which functions to inactivate about 90% of the drug dose to balance the formation of active metabolites. Individuals with low TPMT activity are unable to inactivate the drug methylation and these individuals are at risk for bone marrow toxicity, if they receive standard dose therapy. Therefore, TPMT activity should be assessed prior thiopurine drug administration.

Originally presented on May 20, 2016, in Salt Lake City, Utah.

Lecture Presenter

Kamisha Johnson-Davis, PhD, DABCC

Kamisha Johnson-Davis, PhD, DABCC

Medical Director, Clinical Toxicology
ARUP Laboratories
Associate Professor, Department of Pathology
University of Utah School of Medicine

Dr. Johnson-Davis is an associate professor (clinical) at the University of Utah School of Medicine. She received her BS in biochemistry from the University of California, Riverside, and her PhD in pharmacology from the University of Utah. She was a postdoctoral research associate at the Center for Human Toxicology and completed a postdoctoral fellowship in clinical chemistry at the University of Utah Department of Pathology. Dr. Johnson-Davis is board certified in clinical chemistry and toxicological chemistry. She is a diplomate of the American Board of Clinical Chemistry and a fellow of the National Association of Clinical Biochemistry and the Association of Clinical Scientists.


After this presentation, participants will be able to:

  • Discuss the function of thiopurine drugs and how its metabolism plays a critical role in balancing drug efficacy and drug toxicity.
  • Describe how genetic mutations can impact the function of the thiopurine methyltransferase enzyme
  • Highlight analytical methods that are used to support therapeutic drug management of thiopurine drugs

Sponsored by:

University of Utah School of Medicine, Department of Pathology, and ARUP Laboratories