Figure 1. Algorithm for suggested clinical actions based HLA-B*15:02 and CYP2C9 genotype.
EM, extensive metabolizer; IM, intermediate metabolizer; PM, poor metabolizer
aIf patient has previously used phenytoin for longer than 3 months without incidence of cutaneous adverse reactions, reinitiate phenytoin with caution. Adjust dose based on CYP2C9 genotype if known.
bCarbamazepine should not be used as an alternative (4). Alternative medications such as oxcarbazepine, eslicarbazepine acetate, and lamotrigine have some evidence linking SJS/TEN with the HLA-B*15:02 allele and thus caution should be used in choosing alternatives to phenytoin (see Supplement for details).
cRecommended maintenance dose based on patient’s clinical characteristics