Avoid phenytoin in Han Chinese and Thais

Phenytoin should be avoided if alternative treatment is possible in patients of Han Chinese and Thai origin, warns the MHRA in its latest Drug Safety Update (2010;3: Issue 6) (www. mhra.gov.uk).

    Recent evidence shows that phenytoin is associated with an increased risk of Stevens-Johnson syndrome in people carrying the human leukocyte antigen (HLA) allele HLA-B*1502. The prevalence of this allele in Han Chinese and Thai populations is 8-9 per cent compared with 1-2 per cent in Caucasians; it is also low in Japanese populations.
• The MHRA also offers advice on the risk of nephrogenic systemic fibrosis associated with gadolinium contrast agents, and information about tear-off strips in new patient information leaflets containing key facts for children and adolescents about methylphenidate.