HLA-B*1502 screening and toxic effects of carbamazepine.

To the Editor: Chen et al. (March 24 issue)1 report the absence of the Stevens–Johnson syndrome and its related disease, toxic epidermal necrolysis (SJS–TEN), in subjects who were screened for the HLA-B*1502 allele and were advised not to take carbamazepine if they carried the allele. Case–control studies involving subjects of Han Chinese and Thai origin have also shown an association between SJS–TEN and the receipt of phenytoin, lamotrigine, and oxcarbazepine among HLA-B*1502 carriers.2-4 The Food and Drug Administration has stated that “healthcare providers should consider avoiding phenytoin as alternatives for CBZ [carbamazepine] in patients who test positive for HLA-B*1502.”5 Chen et al. state that lamotrigine and oxcarbazepine were among the alternative medications offered to HLA-B*1502 carriers and did not indicate whether the investigators or treating physicians warned patients not to take phenytoin. The increasing use of HLA-B*1502 screening to prevent carbamazepineinduced SJS–TEN will lead to the replacement of this drug with other anticonvulsants among HLA-B*1502 carriers. Given the availability of other elective therapeutic choices, it may be prudent to advise HLA-B*1502 carriers to avoid not only carbamazepine but also other structurally related anticonvulsants, such as phenytoin, oxcarbazepine, and possibly lamotrigine. Elizabeth J. Phillips, M.D. Simon A. Mallal, M.B., B.S.