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Drug Interaction Between Febuxostat and Thiopurine Antimetabolites: A Review of the FDA Adverse Event Reporting System and Medical Literature
Author(s) -
Logan Jill K.,
Wickramaratne Senarath Yapa Shalini,
Harinstein Lisa,
Saluja Bhawana,
Muñoz Monica,
Sahajwalla Chandrahas,
Neuner Rosemarie,
Seymour Sally
Publication year - 2020
Publication title -
pharmacotherapy: the journal of human pharmacology and drug therapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.227
H-Index - 109
eISSN - 1875-9114
pISSN - 0277-0008
DOI - 10.1002/phar.2362
Subject(s) - febuxostat , medicine , thiopurine methyltransferase , discontinuation , allopurinol , adverse event reporting system , adverse effect , azathioprine , xanthine oxidase , pharmacology , xanthine oxidase inhibitor , concomitant , gout , hyperuricemia , uric acid , biochemistry , chemistry , disease , enzyme
Background There is a known drug interaction (DI) between xanthine oxidase (XO) inhibitors and the thiopurine immunosuppressants, azathioprine (AZA) and mercaptopurine (6‐MP). Xanthine oxidase inhibition increases concentrations of AZA and 6‐MP active metabolites, possibly resulting in myelosuppression. When allopurinol is used with AZA or 6‐MP, dose reduction of AZA or 6‐MP is recommended. Febuxostat is a newer XO inhibitor approved for the treatment of gout. Objective To determine the clinical impact of the febuxostat‐thiopurine DI. Design and Setting Case series derived from the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) and published medical literature. Patients Nineteen patients who received concomitant febuxostat and either AZA or 6‐MP. Measurements Laboratory and clinical data. Results Nineteen cases reporting myelosuppressive events were identified in patients receiving febuxostat with AZA or 6‐MP. Eighteen cases were treated with the combination of AZA and febuxostat. A median of 1.6 months elapsed from initiation of the drug combination until discovery of the event. Sixteen cases required hospitalization; 15 reported administration of blood products. Thirteen cases reported resolution of the event with discontinuation of both drugs, two reported discontinuation of the thiopurine only, and one reported discontinuation of febuxostat only. Limitations Thiopurine monotherapy may cause myelosuppression. Complications of immunosuppression that may contribute to the real‐world morbidity and mortality associated with the febuxostat‐thiopurine DI were not examined. Finally, FAERS data are limited by the voluntary nature of reporting. Conclusion Current febuxostat labeling contraindicates concomitant administration of febuxostat with either AZA or 6‐MP. This case series demonstrates that the DI can result in clinically significant adverse events and is supportive of current febuxostat labeling.