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Case Reports
. 2021 Jan 18;193(3):E94-E97.
doi: 10.1503/cmaj.201022.

Azathioprine-induced severe anemia potentiated by the concurrent use of allopurinol

Lorenzo Madrazo  1 , Emily Jones  2 , Cyrus C Hsia  2
Affiliations
Case Reports

Azathioprine-induced severe anemia potentiated by the concurrent use of allopurinol

Lorenzo Madrazo et al. CMAJ. .
No abstract available

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Conflict of interest statement

Competing interests: None declared.

Figures

Figure 1:
Figure 1:
Hemoglobin (Hb) and white blood cell (WBC) count of a 66-year-old man taking azathioprine. Trend shows a gradual decline in Hb and WBC until the patient was admitted to hospital and azathioprine was stopped at week 12, after which Hb and WBC begin to improve.
Figure 2:
Figure 2:
Pathways of azathioprine metabolism. Allopurinol inhibits the xanthine oxidase (XO) pathway, which normally metabolizes 6-mercaptopurine (6-MP) into 6-thiouracil (6-TU), a nonactive metabolite. Inhibition of the XO pathway leads to shunting toward the hypoxanthine phosphoribosyltransfirase (HPRT) pathway, increasing the production of 6-thioguanine (6-TG), thereby increasing the risk of myelosuppression., Polymorphisms in the thiopurine methyltransferase (TPMT) enzyme can also cause shunting toward production of 6-TG. Hyperactivity in TPMT can increase the risk of hepatotoxicity through the production of 6-methylmercaptopurine (6-MMP).,
See this image and copyright information in PMC

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