Allopurinol-induced Stevens-Johnson syndrome and toxic epidermal necrolysis: Signal detection and preventability from Vietnam National pharmacovigilance database.

WHAT IS KNOWN AND OBJECTIVE: Allopurinol, the first-line medication for hyperuricemia is well-known for its association with severe cutaneous adverse reactions, especially Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). In the current study, we analysed the Vietnamese spontaneous reporting database to identify signals and preventability of allopurinol-induced SJS/TEN in Vietnam from 2010 to 2019. METHODS: Signal generation was assessed using the case/non-case method. Reporting odds ratios (RORs) and 95% confidence intervals (95% CI) were calculated. RESULTS: Among 72,822 spontaneous ADR reports submitted to the Vietnam National Drug Information and Adverse Drug Reaction Monitoring Centre, 392 reports were on SJS/TEN, of which, 65 cases (16.6%) were related to allopurinol. The signals of allopurinol-induced SJS/TEN in Vietnam started in 2014 (ROR of 3.531, 95% CI: 1.830-6.810) and annually increased until 2019 (ROR of 11.923, 95% CI: 8.508-16.710). The preventability assessment showed that no allopurinol-induced SJS/TEN case was definitely unpreventable. 61.6% of the SJS/TEN cases were avoidable because they were associated with inappropriate prescribing such as unapproved indications, too high initial dose and even rechallenging in patients with a history of allopurinol allergy. WHAT IS NEW AND CONCLUSION: The signals of allopurinol-induced SJS/TEN in Vietnam started in 2014 and annually increased until 2019. Our first report specifically focusing on the ADR preventability of allopurinol showed that correction of medical errors relating to prescription could prevent more than 60% of SJS/TEN cases in Vietnamese allopurinol users. This is a feasible and practical solution, provided that there would be a systematic change in both healthcare systems and public awareness.