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Risk of Stevens-Johnson syndrome and toxic epidermal necrolysis during first weeks of antiepileptic therapy: a case-control study. Study Group of the International Case Control Study on Severe Cutaneous Adverse Reactions.

BACKGROUND
There is still controversy about whether all antiepileptic drugs are associated with the severe cutaneous reactions Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). We have studied the role of antiepileptic drugs in SJS and TEN, taking into account potential cofactors that might confound or modify the risk.


METHODS
The case-control study in France, Italy, Germany, and Portugal identified cases of SJS/TEN that developed when the patient was not in hospital and were validated by an expert committee. Controls were patients admitted to the same hospital as the case for an acute illness or an elective procedure.


FINDINGS
73 (21%) of the 352 SJS/TEN cases and 28 (2%) of the 1579 controls reported intake of antiepileptic drugs. Among the 73 exposed SJS and TEN patients, 36 reported intake of phenobarbital, 14 of phenytoin, 21 of carbamazepine, 13 of valproic acid, and three of lamotrigine. Risk was highest in the first 8 weeks after onset of treatment. For individual antiepileptic drugs the univariate relative risk of SJS/TEN for 8 weeks or less of use was 57 (95% CI 16-360; multivariate risk 59 [12-302]) for phenobarbital; 91 (26-infinity) for phenytoin; 120 (34-infinity) for carbamazepine; 25 (5.6-infinity) for lamotrigine, and 24 (5.9-infinity) for valproic acid. The result for valproic acid was based on four case users, all of whom reported concurrent use of other associate drugs. The univariate relative risk for more than 8 weeks of use was 6.2 (2.4-17.0; multivariate risk 2.1 [0.5-9.3]) for phenobarbital, 1.2 (0-5.4) for phenytoin, 0.4 (0.02-2.1) for carbamazepine, and 7.0 (2.4-21.0; multivariate risk 2.0 [0.3-15.0]) for valproic acid.


INTERPRETATION
SJS and TEN are associated with short-term therapy with phenytoin, phenobarbital, and carbamazepine. The association with valproic acid seems to be confounded by concomitant short-term therapy with other causal drugs. Lamotrigine also has the potential for severe skin reactions. The period of increased risk is largely confined to the first 8 weeks of treatment.