Cutaneous adverse drug reactions to allopurinol: 10 year observational survey of the dermatology department – Cagliari University (Italy)

Background  Allopurinol is extensively prescribed for conditions associated with urate excess, despite being responsible for severe cutaneous adverse drug reactions (ADR). Objective  A cross-sectional survey of allopurinol cases observed at the main Dermatology Department with inpatients facilities in southern Sardinia. (approx 560 836 inhabitants). Material and methods  Data collection of all consecutive patients referred for ADR between 2001 and 2010. Causality assessment followed the WHO Collaborating Centre for Drug Monitoring criteria; illness severity score was adopted for toxic epidermal necrolysis (SCORTEN). Results  Allopurinol was the culprit drug in 84 of 780 cutaneous ADR cases (10.7%; 8.4 cases/year). Mean age was 74 years, 58% of the patients were female, 95% of patients required hospitalization. Clinical forms were maculo-papular eruptions (34 cases), Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (31 cases), vasculitis (six cases), Drug Rash Eosinophilia and Systemic Symptoms (DRESS) (three cases), Acute Generalized Exanthematous Pustolosis (AGEP) (three cases), Pityriasis rosea-like eruption (three cases), lichenoid dermatitis (two cases), fixed drug eruption (one case), erythroderma (one case). The indication for allopurinol prescription was asymptomatic hyper-uricemia in 95% of the patients. Twelve patients were under allopurinol dosage adjustment according to creatinine clearance. Final causality assessment was definite for 12% of the cases and probable for the remaining 88%. Full recovery was achieved in 88% of subjects; ten SJS/TEN patients died (12% overall mortality; 32% mortality of the SJS/TEN cases). Conclusion  Considering the populations size of Southern Sardinia, is plausible that 1.5/100 000 Sardinian will be affected by allopurinol related ADR per year. Advanced age, and inappropriate allopurinol prescription were the main conditions affecting morbidity and mortality.