The U.S. Food and Drug Administration approved the first prescription drug derived from the marijuana plant, as a treatment for rare forms of epilepsy that primarily afflict children. The drug, called Epidiolex, is an oral solution containing highly purified cannabidiol (CBD), which is one of scores of chemicals in the cannabis sativa plant, commonly known as marijuana. The drug contains only trace amounts of the psychoactive element THC and does not induce euphoria. Epidiolex was approved for patients age 2 and older who suffer from Lennox-Gastaut and Dravet syndromes. Both cause uncontrolled daily seizures and put patients at high risk for other physical and intellectual disabilities, injury and early death. The disorders afflict fewer than 45,000 people in the United States, but experts expect Epidiolex to be prescribed for other types of epilepsy as well. The drug is the first treatment approved for Dravet syndrome. The medication, tested in three randomized, placebo-controlled trials with more than 500 patients, was effective in reducing seizures, the FDA said.