Prepared by Britain's GW Pharmaceuticals, Epidiolex uses purified cannabidiol, or CBD, which is one of more than 80 active components of the cannabis plant.
"This is a major medical breakthrough," said Commissioner Scott Gottlieb of the Food and Drug Administration (FDA, for its acronym in English).
"But it's also important to note that this is not an approval of marijuana or all of its components. It is the approval of a specific CBD drug for a specific use, "he added.
The drug was approved to treat the Lennox-Gastaut (LGS) and Dravet syndromes, types of epilepsy cause severe seizures, in patients of two or more years of age, says the FDA.
Dravet syndrome is a rare genetic condition that causes frequent seizures related to fever, involuntary muscle spasms and continuous life-threatening seizures, which require emergency medical attention.
Children who suffer from it "typically experience poor language and motor skills development, hyperactivity, and difficulties in relating to other people," the FDA said.
Like the Dravet syndrome, the Lennox-Gastaut syndrome also begins in childhood and causes multiple types of seizures, while the majority of affected children experience learning problems, intellectual deficiency and need help with their daily activities.
"For those who live with intractable seizures caused by the LGS and Dravet syndromes, Epidiolex represents a true medical breakthrough," said Philip Gattone, president and CEO of the Foundation for Epilepsy.
Before the drug can be marketed, the FDA must reclassify the CBD, which is considered a drug with a high risk of abuse and without medical value because it is derived from marijuana.
This procedure is expected to be completed in 90 days, according to GW Pharmaceuticals, which will market the medicine through its subsidiary Greenwich Biosciences.
The European Medicines Agency is currently reviewing the use of Epidiolex to treat seizures linked to the LGS and Dravet syndromes and its decision is expected next year.
The effectiveness of Epidiolex was studied in three randomized trials involving 516 patients with one of the syndromes, in order to compare the use of the drug with that of a placebo.
