The FDA approved GW Research's cannabidiol (CBD) for the treatment of two rare and severe forms of epilepsy, Lennox–Gastaut syndrome and Dravet syndrome. This was the first FDA approval for a drug that contains a purified drug substance derived from marijuana.

“This approval serves as a reminder that advancing sound development programs that properly evaluate active ingredients contained in marijuana can lead to important medical therapies,” said FDA commissioner Scott Gottlieb. “We'll continue to support rigorous scientific research on the potential medical uses of marijuana-derived products and work with product developers who are interested in bringing patients safe and effective, high-quality products.”

Researchers have previously reported anti-inflammatory, anti-emetic, neuroprotective and anticancer activity with CBD (Nature Reviews Drug Discovery 3, 771–784; 2004). CBD's activity is distinct from the effects of tetrahydrocannabinol (THC), which causes the intoxication and euphoria associated with marijuana.

GW and others are also developing CBD and THC for other indications. Insys Therapeutics has initiated phase III trials of CBD in seizure disorders and infantile spasms, as well as phase II trials in Prader–Willi syndrome. GW is testing its GWP42003 formulation of CBD for schizophrenia and other indications. GW's nabiximols, a combination of CBD and THC, is in phase III trials for neuromuscular spasm and spasticity (and already approved in this setting in many countries in the European Union and elsewhere). And Intec Pharma is trialling a combination of CBD and THC in phase I for pain.

Dronabinol, first approved by the FDA in 1985 for chemotherapy-induced nausea and vomiting, is a synthetic form of THC.