Examining the use of allopurinol: Perspectives from recent drug injury relief applications

Background/purpose: Previous studies have reported that the indication and starting dose of allopurinol may be associated with the incidence of hypersensitive reactions. As allopurinol-related severe cutaneous adverse reactions (SCARs) constitute a significant proportion of drug injury relief applications in Taiwan, this study sought to examine allopurinol use and related adverse reactions through an analysis of recent drug injury relief applications. Methods: Allopurinol-related drug injury relief applications from 1999 to 2016 were collected, and descriptive statistical methods were used to analyze recent applications dating from 2011 to 2016. Results: A total of 174 allopurinol-related drug injury relief applications were submitted between 2011 and 2016, with the majority involving cases over the age of 65 (75.3%; mean age of all cases was 69.2). Most allopurinol-related drug injuries concerned the skin (173 out of 174 cases, 99.4%). The majority of cases had other co-morbidities such as cardiovascular disease/hypertension (86.2%), chronic kidney disease (58.6%), or diabetes (46.6%). Over 70% of cases initiated allopurinol at a dose of 100 mg/day or less. Analysis revealed that the greatest number of cases (44.6%) occurred in those with an estimated glomerular filtration rate (eGFR) between 15 and 60 mL/min/1.73 m2 and who initiated allopurinol at a dose of 100 mg/day. Conclusion: Old age and renal dysfunction are key risk factors for allopurinol hypersensitivity. When considering allopurinol for elderly patients with impaired kidney function, a full risk-benefit assessment, dosage adjustments, and careful monitoring may be warranted. Keywords: Allopurinol, Compensation and redress, Drug-induced Stevens-Johnson syndrome, Taiwan, Toxic epidermal necrolysis