Table 3.

The DPWG Phenytoin Dosing based on HLA-B*15:02 Genotype (2017)

GenotypeImplicationDosing recommendations
Positive for HLA-B*15:02Increased risk of the life-threatening cutaneous side effect Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). The calculated risk of phenytoin-induced SJS/TEN in individuals with HLA-B*15:02 is 0.65%.Carefully weigh the risk of SJS/TEN against the benefits
Avoid phenytoin if an alternative is possible
  • Carbamazepine has a 10-fold higher risk of SJS/TEN for these individuals and is therefore not an alternative.
  • A comparable risk has been reported for lamotrigine as for phenytoin. The same applies for oxcarbazepine, but the most severe forms (SJS/TEN overlap and TEN) are not observed with oxcarbazepine.
If it is not possible to avoid this medication, then advise the individual to report any skin rash immediately

This DPWG table is adapted from (3).

From: Phenytoin Therapy and HLA-B*15:02 and CYP2C9 Genotype

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