A rising number of epileptic patients are using an alternative medicine to reduce their seizures. The herb in question is Cannabis sativa. Among the users are some of the almost 100,000 American children who have “intractable epilepsy,” which does not respond to standard antiseizure medications. Some parents report that marijuana helps to control their child's seizures when other standard drugs do not.

There is no pharmaceutical preparation of cannabis as a drug. Instead parents must personally buy pot at a medical marijuana dispensary—or perhaps illegally—to help their child.

The isolation of a chemical in marijuana that may be involved with tamping down seizures could soon change all that. Cannabidiol is a purified compound derived from cannabis that shows promise in treating epilepsy in both adults and children. The chemical, which also is responsible for some of the other health benefits associated with medical marijuana, is the main active ingredient in a new drug under investigation, called Epidiolex, manufactured by GW Pharmaceuticals. Epidiolex contains several other cannabinoid compounds but is formulated without tetrahydrocannabinol, the compound that makes people feel high.

As with some approved seizure medications, researchers do not understand exactly how cannabidiol functions as an anticonvulsant. Whatever its physiological underpinnings, cannabidiol seems to work. Animal studies and preliminary investigations with human adults suggest it significantly reduces seizures and is well tolerated and safe.

Now researchers are making formal efforts to test cannabidiol in children with intractable epilepsy. A year-long clinical trial will test whether it diminishes epileptic activity in 150 children who have not been helped by standard seizure medications. If Epidiolex proves itself, it will supply additional evidence that marijuana may serve as a potential cornucopia of medical leads to be used for future drug development.