NEW YORK (GenomeWeb News) – Patients of Asian ancestry taking the drug carbamazepine will now be advised to take a genetic test to determine whether they have a heightened risk of developing a rare but serious skin reaction, the US Food and Drug Administration said in a statement today.
Carbamazepine treats epilepsy, bipolar disorder, and neuropathic pain, and is sold under the brand names Carbatrol, Equetro, and Tegretol by Shire Pharmaceuticals, Validus Pharmaceuticals, and Novartis, respectively.
The FDA said the drug can in some instances cause life-threatening skin reactions including toxic epidermal necrolysis and Stevens-Johnson syndrome, which is characterized by skin lesions, blisters, fever, itching, and other symptoms.
The genetic predisposition for adverse reactions is much greater among people who have the HLA-B* 1502 human leukocyte antigen allele. This allele occurs almost exclusively in patients with Asian ancestry – a population that comprises around 5 percent of patients being considered for treatment with carbamazepine, the FDA said.
The FDA said the risk for adverse reactions to carbamazepine is between 1 and 6 per 10,000 new users in countries with mainly white populations, but it may be around ten times higher in Asian countries.
The FDA recommends a blood-based genetic test for the gene and notes that patients who test positive for the HLA-B* 1502 allele should not be treated with carbamazepine “unless the benefit clearly outweighs the increased risk of these serious skin reactions.”
Further information on the relabeling is available here.