Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline forCYP2C9andHLA-BGenotypes and Phenytoin Dosing: 2020 Update

Phenytoin is an antiepileptic drug with a narrow therapeutic index and large interpatient pharmacokinetic variability, partly due to genetic variation inCYP2C9. Furthermore, the variant alleleHLA-B*15:02is associated with an increased risk of Stevens-Johnson syndrome and toxic epidermal necrolysis in response to phenytoin treatment. We summarize evidence from the published literature supporting these associations and provide therapeutic recommendations for the use of phenytoin based onCYP2C9and/orHLA-Bgenotypes (updates on cpicpgx.org).

Automated summary

Phenytoin, an antiepileptic drug, is influenced by genetic variations in patients, with individuals carrying the variant allele HLA-B*15:02 having an increased risk of severe skin reactions when receiving phenytoin treatment.