Allopurinol response

Allopurinol is widely prescribed for the treatment of hyperuricemia and gout. An estimated 25-30% of gout patients in the UK and the US are treated with allopurinol. However, 0.1-0.4% of patients treated with allopurinol experience severe cutaneous adverse reactions (SCAR), including drug hypersensitivity syndrome, Stevens-Johnson syndrome, and toxic epidermal necrolysis. The genetic variant HLA-B*58:01, along with non-genetic factors, is known to be associated with this risk. Patients who are HLA-B*58:01-positive (having at least one copy of the HLA-B*58:01 allele) have a significantly increased risk of allopurinol-induced SCAR compared to those who are negative for this allele. It is still possible for a HLA-B*58:01 negative patient to develop SCAR on allopurinol. Guidelines regarding the use of pharmacogenomic tests in dosing for allopurinol have been published in Clinical Pharmacology and Therapeutics by the Clinical Pharmacogenetics Implementation Consortium (CPIC) and are available on the PharmGKB website.

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