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Drug Safety-related Labeling Changes (SrLC)

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IMURAN (NDA-016324)

(AZATHIOPRINE)

Safety-related Labeling Changes Approved by FDA Center for Drug Evaluation and Research (CDER)

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12/20/2018 (SUPPL-39)

Approved Drug Label (PDF)

5 Warnings and Precautions

(Additions and/or revisions are underlined)

WARNINGS:

Cytopenias

Patients with thiopurine S-methyl transferase (TPMT) or nucleotide diphosphatase (NUDT15) deficiency may be at an increased risk of severe and life-threatening myelotoxicity if receiving conventional doses of IMURAN. Death associated with pancytopenia has been reported in patients with absent TPMT activity receiving azathioprine. In patients with severe myelosuppression, consider evaluation for TPMT and NUDT15 deficiency. Consider alternative therapy in patients with homozygous TPMT or NUDT15 deficiency and reduced dosages in patients with heterozygous deficiency.

PRECAUTIONS:

Laboratory Tests: Complete Blood Count (CBC) Monitoring:

TPMT and NUDT15 Testing: Consider genotyping or phenotyping patients for TPMT deficiency and genotyping for NUDT15 deficiency in patients with severe myelosuppression. TPMT and NUDT15 testing cannot substitute for complete blood count (CBC) monitoring in patients receiving IMURAN.

6 Adverse Reactions

ADVERSE REACTIONS:

(Additions and/or revisions are underlined)

Hematologic:

… Patients with low or absent TPMT or NUDT15 activity are at increased risk for severe, life-threatening myelosuppression from IMURAN.

7 Drug Interactions

(Additions and/or revisions are underlined)

Drug Interactions: Use with xanthine oxidase (XO) inhibitors: One of the pathways for inactivation of azathioprine is inhibited by XO inhibitors (allopurinol or febuxostat). Patients receiving IMURAN and allopurinol concomitantly should have a dose reduction of IMURAN, to approximately 1/ 3 to 1/ 4 the usual dose. Concomitant use of IMURAN with febuxostat is not recommended. Inhibition of XO may cause increased plasma concentrations of azathioprine or its metabolite, 6-MP, leading to toxicity. It is recommended that a further dose reduction or alternative therapies be considered for patients with low or absent TPMT activity receiving IMURAN and xanthine oxidase inhibitors because both TPMT and XO inactivation pathways are affected.