A new drug derived from marijuana just became the first of its kind to get the green light from the US government.

Called Epidiolex, the drug is designed to treat two rare forms of childhood epilepsy using a cannabis compound called cannabidiol (or CBD).

British-based GW Pharmaceuticals makes the drug. It does not contain THC, the well-known psychoactive component of marijuana responsible for the drug’s characteristic high.

The federal thumbs-up comes on the heels of several months of promising research results and a positive preliminary vote from the Food and Drug Administration this spring. Experts are hopeful that the approval will unleash a wave of new interest in the potential medical applications of CBD and other marijuana compounds.

“This approval serves as a reminder,” Scott Gottlieb, the FDA commissioner, said in a statement on Monday, “that advancing sound development programs that properly evaluate active ingredients contained in marijuana can lead to important medical therapies.”

In three large clinical trials which the FDA considered before giving Epidiolex the official green light, researchers presented strong evidence that the pharmaceutical-grade CBD in the medicine had the power to significantly curb some of the worst symptoms of two of the hardest-to-treat forms of epilepsy, known as Lennox-Gastaut syndrome and Dravet syndrome.

“This is clearly a breakthrough drug for an awful disease,” John Mendelson, a panel member and senior scientist at the Friends Research Institute, said at a public FDA meeting this spring that was called to discuss the scientific merits of the drug.

But although the green light means that patients will soon be able to access Epidiolex with a doctor’s prescription, many will also likely turn to less expensive sources of CBD, such as those sold in marijuana dispensaries. Researchers and advocates cautioned against this, however, with the caveat that it’s impossible to verify that what’s in those products is actually pharmaceutical-grade CBD.

Starting last spring with a study presented at the American Academy of Neurology’s yearly meeting in Boston, GW Pharmaceuticals has consistently presented strong clinical studies that appear to support Epidiolex.

“There’s a boatload of evidence to show for this drug at this point,” Orrin Devinsky, a lead author on one of those studies and a neurologist at NYU Langone Health.

A month after the Neurology meeting, Devinksy and his colleagues published a positive study of the drug in children with Dravet syndrome in the New England Journal of Medicine. Roughly 43% of the children in that study who got the drug saw their number of seizures cut in half, and 5% stopped having seizures entirely. In comparison, children who got a placebo had barely any noticeable change in their symptoms.

Almost exactly a year later, Devinksy and his team followed up those results with another favorable study in the same journal using a smaller dose of the drug in patients with Lennox-Gastaut. Devinsky said that low dose might be “the sweet spot” where most patients can achieve relief from symptoms without any unwanted side effects, such as drowsiness.

Also, although Epidiolex is designed to treat only two types of epilepsy, medical professionals and marijuana doctors in florida can technically prescribe it “off-label” for other conditions as well. (The anesthetic ketamine, for example, is prescribed this way for some hard-to-treat forms of depression.)

“We would expect that once this is approved as a drug it’s quite likely this will be tried in other populations off-label so it has a big opportunity to affect others,” Lubbers said.

Epidiolex vs. other CBD products

Scientists and advocates representing families of patients with epilepsy are hailing Epidiolex’s arrival as a long-awaited treatment. But they are also aware that desperate patients — especially parents of young children — may actively seek alternate sources of CBD that may be cheaper and don’t require a doctor’s prescription.

In states where marijuana is legal (or in states with laws legalizing CBD on its own), oils and salves made with CBD are widely available. But experts caution that these products may not be what they seem.

“What’s different with [Epidiolex] is that this is a well-studied and well-controlled product,” Laura Lubbers, the chief scientific officer of a nonprofit called Cure that funds epilepsy research.

But most dispensary-grade CBD products are not well-studied or well-controlled.

For a 2017 study published in the Journal of the American Medical Association, researchers tested 84 products purchased from 31 different online CBD sellers. Roughly seven out of 10 items had different levels of CBD than what was written on the label. Of all of the items they tested, roughly half of the items had more CBD than was indicated; a quarter had less. And 18 of the samples tested positive for THC, despite it not being listed on the label.

“The main thing is that CBD as approved by the FDA is pharmaceutical-grade CBD. It’s manufactured under stringent standards, the same as other FDA-approved drugs,” Shlomo Shinnar, the president of the American Epilepsy Society and a professor of neurology and epidemiology at the Albert Einstein College of Medicine. “That’s not the same as when people tell you, ‘Oh, I’ve got marijuana and it’s high in CBD,’ or ‘Oh, I’ve got a CBD product.'”

Epidiolex’s approval could also be a powerful catalyst for deeper research into other marijuana-derived medicines. Cannabis has more than 400 compounds, of which CBD and THC are only two, and researchers think the others could hold promise as well.

The drug’s green light also means that the Drug Enforcement Agency now has 90 days to reschedule CBD, which it listed in January of last year as a “marijuana extract” separate from “marijuana” or THC.

That means instead of being listed alongside marijuana as a Schedule 1 drug with “no currently accepted medical use,” CBD will soon be categorized as either a Schedule 2 or 3 drug, much like the popular ADHD medication Adderall.

Once that happens, it’ll unleash what Carreno called a “sea change” for CBD manufacturers and the industry as a whole, which up until this point has existed in a legal grey area.

Apart from CBD, researchers are also actively studying THC and other marijuana compounds for a range of potential medical uses, from relieving pain to soothing severe nausea. Although Epidiolex is the first marijuana plant-based drug to land FDA approval, the agency has already given the green light to drugs whose active ingredient is a lab-made version of THC, for example.

In the meantime, experts look forward to seeing Epidiolex made available to patients in need.