Azathioprine

Pharmacogenomic Information in the Context of the FDA-Approved Drug Label*

The FDA recommends, but does not require genetic or phenotypic testing for TPMT.

Excerpt from the azathioprine drug label:

"It is recommended that consideration be given to either genotype or phenotype patients for TPMT."

Patients with low or absent TPMT activity who are treated with conventional doses of azathioprine are at increased risk for severe, life-threatening myelosuppression resulting from treatment with azathioprine. Patients with intermediate TPMT activity may be at increased risk of myelotoxicity when given conventional azathioprine doses. Physicians may consider alternative therapies for patients homozygous for non-functional TPMT alleles(most commonly associated with the alleles TPMT*2, TPMT*3A, and TPMT*3C), and dose reduction is recommended for heterozygous patients with reduced TPMT activity. Approximately 10% of Caucasians and African Americans carry one non-functional TPMT allele and exhibit intermediate TPMT activity, while 0.3% are homozygous for non-functional TPMT alleles, yielding low or absent TPMT activity.

For the complete drug label text with sections containing pharmacogenetic information highlighted, see the Azathioprine drug label PDF.

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