Incidence of Stevens–Johnson syndrome following combination drug use of allopurinol, carbamazepine and phenytoin in Taiwan: A case–control study

The goal of our study was to investigate the incidence of Stevens–Johnson syndrome (SJS), the frequency of SJS diagnosis, and the association between SJS and prior use of allopurinol, carbamazepine or phenytoin. This case–control study utilized data from the National Health Insurance Research Database (NHIRD) of Taiwan. Controls visited the emergency department of the same hospital for trauma or fractures (excluding burns) and used allopurinol, carbamazepine or phenytoin during the past 3 months. We determined whether patients were prescribed a combination of drugs in addition to allopurinol, carbamazepine or phenytoin within the last 3 months. We identified 1 853 985 controls and 7327 SJS-diagnosed patients using the Taiwan NHIRD records for 2000–2008. Higher use of allopurinol (49.8%), carbamazepine (39.1%) or phenytoin (21.3%) was observed among patients (n = 3131) than among controls (n = 2858). The overall SJS incidence rate was 3.6/1 000 000. Drug combinations were uncommon (<10%) in patients or controls taking allopurinol. However, combination drug use exceeded 10% in patients taking carbamazepine or phenytoin. Logistic regression analysis of recent combination drug use revealed that phenobarbital, valproate, non-steroidal anti-inflammatory drugs (NSAIDs) including piroxicam and tenoxicam, and antibiotics including amoxicillin and cephalexin were strongly associated with SJS. Patients with gout or epilepsy taking allopurinol, carbamazepine or phenytoin should be evaluated carefully by physicians. Concurrent use of piroxicam, tenoxicam, phenobarbital, valproate, amoxicillin or cephalexin, in addition to carbamazepine or phenytoin, may increase the incidence of SJS.