Azathioprine isn’t a drug I see terribly often in clinical practice, but there are some really important things to remember. I recently put together a podcast on azathioprine and I wanted to share some of my top azathioprine clinical pearls with you.
Azathioprine Clinical Pearls – Monitoring Parameters
Azathioprine can cause a significant number of toxicities and there are some very important monitoring parameters to remember. The most important one in my opinion is CBC. Azathioprine is an immunosuppressive agent and monitoring white blood cell count and for the risk of infection and malignancy is critical. There is a boxed warning with the use of azathioprine as it can cause malignancy.
In addition to CBC alterations, LFT monitoring is going to be important as the drug is implicated as a common cause of drug-induced liver impairment.
Azathioprine is broken down into active metabolites. Those active metabolites are eventually broken down by a couple of critical processes. Thiopurine methyltransferase (TPMP) is one of those critical pathways that essentially end the activity of azathioprine. In patients who are poor metabolizers via thiopurine methyltransferase, there is a significantly increased risk for toxicity. Another enzyme that is responsible for the inactivation of azathioprine’s active metabolites is nudix hydrolase 15 (NUDT15). TPMT is actually recommended by the AGA prior to using azathioprine. I cover more important pharmacogenomic pearls in our Board Certification All Access Packages.
Major Drug Interaction
Allopurinol doesn’t have a lot of significant drug interactions, but the one with azathioprine is definitely one to remember. Allopurinol can significantly increase the concentrations of azathioprine which can lead to toxicity. Other drug interactions would include medications that can cause hepatotoxicity and additive effects on myelosuppression. It is also imperative to remember the effects that immunosuppressive agents can have on the clinical response to vaccines.
If you’d like to learn more azathioprine clinical pearls, check out my recent podcast at Real Life Pharmacology!
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