It tastes of strawberry, but Epidiolex is the first drug approved in the US containing an ingredient from marijuana.
The US Food and Drug Administration (FDA) approved the drug on 25 June for the treatment of two rare but severe forms of childhood epilepsy: Dravet syndrome and Lennox-Gastaut syndrome.
The active ingredient in the drug is cannabidiol, and it contains only a trace of the psychoactive component of cannabis, tetrahydrocannabinol, or THC.
In clinical trials, Epidiolex proved effective at helping people with these conditions control their seizures.
“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 Scott Gottlieb, FDA commissioner.
But he warned that the organisation would continue to punish illegal marketing of cannabidiol-containing products with unproven medical claims.
The UK government last week announced a review into the possible use of marijuana-based medical products, in the wake of much public debate over the use of cannabis oil to treat epilepsy.
GW Pharmaceuticals, which developed Epidiolex, expects a decision on European approval early next year. In 2010, it won UK approval to sell Nabiximols for the treatment of multiple sclerosis, the first marijuana-based drug approved in the world.
The company is also developing cannabis-based treatments for epilepsy, schizophrenia and glioblastoma, a form of brain cancer for which there are no reliable treatments.