FDA Strengthens Warnings
On Some Epilepsy Drugs
- The Wall Street Journal
12/12/2007 - The Food and Drug Administration Wednesday strengthened warnings on certain drugs used to treat epilepsy, bipolar disorder and nerve pain, discussing the possibility of rare skin disorders and recommending that patients with Asian ancestry undergo genetic testing before using the drugs.
Carbamazepine is a drug used for treatment of epilepsy, bipolar disorder and nerve pain. The drug is available as a generic and is sold under the brand names Carbatrol by Shire PLC, Tegretol by Novartis AG, and Equetro by Validus Pharmaceuticals Inc., a privately-held firm.
The FDA said the prescribing information for the drugs already carried a warning about the possibility of rare but severe -- and sometimes life-threatening -- skin reactions for all patients starting carbamazepine therapy. The skin reactions include toxic epidermal necrolysis and Stevens-Johnson syndrome, characterized by multiple skin lesions, blisters, fever, itching, the agency said.
However, the warning will be moved to a more prominent location on the drugs' labels and be placed in an existing black box warning that discussed risks for developing anemia. A black-box warning is the FDA's toughest drug warning and appears at the top of a drug's label.
The new recommendation that health care providers give patients with Asian ancestry a genetic test before starting treatment will also be added to the boxed warning section. The FDA said the manufacturers of carbamazepine-containing drugs have agreed to the labeling change.
The FDA said the risk of the skin reactions is estimated to be about 1 to 6 per 10,000 new users of the drug in countries with mainly white populations, but the risk in Asian populations is estimated to be about 10 times higher.
The FDA said studies have found a strong association between certain serious skin reactions and an inherited variant of a gene, HLA-B* 1502, which is found almost exclusively in people with Asian ancestry. Patients can find out if they have the gene by undergoing a blood test which is then sent into a laboratory for analysis.
The agency said patients who test positive for the gene should not be treated with carbamazepine unless the benefit clearly outweighs the increased risk of these serious skin reactions.
The FDA said patients who've taken carbamazepine for more than a few months and have not experienced any skin reactions are unlikely to ever experience these reactions, regardless of ancestry or genetic test results.
Patients currently taking carbamazepine who are concerned the skin reactions shouldn't stop taking the drug without first consulting their health care provider, the FDA said. |
