COLORADO SPRINGS, Colorado (AP) - The U.S. Food and Drug Administration is expected to decide soon whether to give its first approval to a prescription drug made from the marijuana plant.

But parents who have used other products containing chemicals from the plant to treat their children's severe forms of epilepsy are feeling more cautious than celebratory. They want assurance that existing medical marijuana markets in more than two dozen states won't be harmed if the drug called Epidiolex (Eh-peh-DYE'-oh-lex) gets approved.

In particular, some advocates worry that drugmaker GW Pharmaceuticals has lobbied for changes to several states' definition of marijuana, seeking legal cover for pharmacies to sell cannabis-derived products that have the FDA's backing.

A company representative says GW Pharmaceuticals only wants to ensure its product can reach patients.