Allergic skin reactions to anticonvulsant medications in patients receiving cranial radiation therapy

Purpose: Erythema multiforme and Stevens-Johnson syndrome have been associated with anticonvulsant medications (AEDs) in patients with brain tumors receiving cranial irradiation. AEDs are also known to cause mild drug rashes. The incidence of these complications has not been well studied among patients with brain tumors. We reviewed the records of patients with brain tumors treated with cranial radiation and AEDs to assess the frequency of both severe and mild skin reactions. Methods: Retrospective review of 289 radiotherapy records of consecutively treated patients from 1988 to 1993. Results: Only one of 289 patients developed erythema multiforme. Milder rashes, however, occurred in 18% of exposures to AEDs including 22% of exposures to phenytoin, compared with the expected rate of 5-10%. Most of the mild drug rashes occurred before the initiation of radiotherapy, suggesting that radiation was not the cause of these reactions. Conclusions: Severe skin rashes are rare among patients with brain tumors receiving radiation therapy and AEDs, There is, however, an increased frequency of mild drug rashes among patients with brain tumors that does not appear related to radiation.