Carbamazepine is used for the treatment of epilepsy and is commonly used as a mood stabilizer for bipolar spectrum disorders.23 Recently published CPIC guidelines strongly support HLA-B*1502 genotyping for patients of Asian ancestry who are being considered for the treatment with carbamazepine.27 CPIC guidelines followed changes to the product labeling in 2007, which incorporated the use of pharmacogenomic testing into the black-box warning section.23 This warning highlights the risk of severe and potentially fatal dermatologic reactions, Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN). Both the FDA labeling and CPIC guidelines recommend genetic testing for presence of the HLA-B*1502 allele in patients of Asian ancestry.23, 27 The guidelines for testing highlight distinct ethnic and regional differences in the distribution of the risk allele that should be considered when evaluating who should be tested. The HLA-B*1502 polymorphisms are found in the highest frequencies in Asian populations (10–15% in patients from China, Thailand, Malaysia, Indonesia, the Philippines, and Taiwan; 2–4% in patients from south Asia and India), with extremely low or nonexistent(<0.01%) in patients of European, Hispanic, Native American, and African descent.28
