CPIC publishes guidelines on interpreting genetic test results for HLA-B*5801 when prescribing allopurinol therapy.

Allopurinol is an analog of the purine base hypoxanthine. It inhibits the conversion of hypoxanthine and xanthine to uric acid by XDH and is used in the treatment of gout.  Severe cutaneous adverse reaction, SCAR, also known as allopurinol hypersensitivity syndrome, is a rare serious and sometimes fatal side effect that occurs in an estimated 0.1 to 0.4% of allopurinol-treated patients.  SCAR is manifested by Stevens-Johnsons Syndrome (SJS), Toxic Epidermal Necrolysis (TEN) or drug reaction with eosinophilia and systemic symptoms (DRESS). 

There is substantial evidence linking HLA-B*5801 with allopurinol-induced SCAR [see Articles: 15743917, 18192896, 19018717, 19696695, 21301380, 21393610, 21545408].  A recent meta-analysis pooling all the published studies gave the odds ratios for allopurinol induced SCAR in HLA-B*5801 carriers as 73 and 165 for studies using healthy controls and allopurinol tolerant controls, respectively [Article: 21906289]. 
A multinational team of rheumatologists, clinicians and pharmacogenomics researchers evaluated the evidence on HLA-B*5801 and allopurinol-induced SCAR. The CPIC guidelines recommend that allopurinol not be used in patients who are known carriers of HLA-B*5801.

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Please click here to see excerpts from the guideline and access downloads of the article and supplement . 

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