Allergic rash due to antiepileptic drugs: clinical features and management.

Optimal management of allergic rash from antiepileptic drugs (AEDs) is unclear. We identified 50 patients with 68 reactions (36 to one AED, 10 to two AEDs, and four to three AEDs). The AEDs implicated were carbamazepine, 30; phenobarbital (PB), 20; phenytoin, 16; ethosuximide, one; and AED combination, one. Sixty-three reactions were cutaneous eruptions, three exfoliative dermatitis, and two Stevens-Johnson syndrome. Forty-six reactions were mild (rash only), 18 moderate (systemic symptoms or other organ system involvement), and four life-threatening (all with PB). In most patients with greater than 1 reaction, the second and third reactions were not more severe than the first. Prior antibiotic allergies or nonmedication allergies were no more common than in a control group without reactions. The AED was ceased abruptly in 59 patients (22 of whom did not receive a new AED), tapered in five, and continued unchanged in four. Despite this, there was no status epilepticus (SE) during the reaction or its treatment, and no patient's seizure control deteriorated. In 40 cases, a new AED was added--16 after the reaction had resolved and 24 before total resolution. Rash recurred with the new AED in 50 and 42% respectively (NS). We conclude that, though allergic rashes to AEDs are usually mild, the rare occurrence of severe reactions indicates that the AED should be ceased. This can be done abruptly with minimal risk of SE. A new AED can be added, if necessary, prior to the resolution of the rash without increasing the risk of further reactions.