SCIENCE / MEDICINE : Humidity Erodes Epilepsy Drug

A drug used to prevent epileptic seizures can lose a third of its effectiveness if stored in humid conditions, according to study results released last week by the Food and Drug Administration. The results prompted the FDA to renew its advice that drugs be stored in a cool, dry place.

The FDA is asking manufacturers of the epilepsy drug, carbamazepine, to change their packaging of the drug to keep out moisture. Users of the drug should keep their supplies tightly closed in a dry location, away from bathrooms, showers and humidifiers, the agency said.

The studies may help explain why some patients taking carbamazepine have complained that the drug’s ability to prevent seizures varies, the FDA said.

The research, conducted at FDA laboratories in Washington and in FDA-funded studies at the University of Tennessee College of Pharmacy in Memphis, found that when carbamazepine tablets were exposed to humidity, they hardened and then dissolved poorly in test liquids.