So, it finally happened—in June 2018, the FDA fully approved Epidiolex, the CBD medicine for two epilepsy syndromes. Cannabidiol, or CBD for seizures, has long been a subject of study—but apart from being a first for cannabis in FDA history, this approval is considered a big win for the medical marijuana industry in general. It is also the first-ever approved medication to treat seizures typical to Dravet syndrome.
Yet this is neither unexpected nor a huge surprise. Globally and in the U.S., anecdotes abound of desperate patients reverting to this compound as a last resort to treat refractory epilepsy—with excellent results.
Science is not far behind, though, and so far it has demonstrated that CBD is not only effective in bringing seizures under control but also that it is very well tolerated. In fact, study outcomes were so promising that the FDA has granted Epidiolex, or Cannabidiol (its generic name), not only “Priority Review,” but also “Fast Track” and “Orphan Drug” designations. Without going into too many details—these are the kind of concessions a licensing applicant gets when it is clear to the FDA that the product is likely to be extremely helpful and safe for use to prospective patients. 
In a recent FDA press announcement and an NBC interview that sounds almost defensive, FDA management was quick to stress that this drug approval doesn't automatically make medicinal marijuana legal across the board.
Dr. Scott Gottlieb, FDA Commissioner, stated, “This is a purified form of CBD. It’s being delivered to patients in a reliable dosage form and through a reproducible route of delivery to ensure that patients derive the anticipated benefits...This is an important medical advance. But it’s also important to note that this is not an approval of marijuana or all of its components. This is the approval of one specific CBD medication for a specific use.”
He went on to warn the public against unproven claims for the use of CBD and explained that the FDA processes are in place to protect against snake-oil vendors.
“The promotion and use of these unapproved products may keep some patients from accessing appropriate, recognized therapies to treat serious and even fatal diseases,” Gottlieb said.
Also, there is an ongoing tango between federal and state law regarding CBD legality, as federally, marijuana and all its constituents and derivatives are still classified as an illegal Schedule I drug.
However, moves in the direction of excluding CBD from this legislation have already started. In May, the Drug Enforcement Administration (DEA) released an internal directive that basically excluded some CBD products from the classical definition of marijuana, also spelled “marihuana.” Some states are following suit, but official U.S. law still needs to change accordingly. 
This FDA approval is a massive scientific validation of the many benefits of CBD, though, and medical marijuana lobbyists and advocates consider the move to be very encouraging.
Epidiolex, the first-ever drug to get the approval of CBD for epilepsy from the FDA, has gotten the thumbs-up for use in the Lennox-Gastaut and Dravex syndromes for patients of two years and older. These two are rare and very severe forms of epilepsy.
CBD is a marijuana compound without psychoactive activity, and it has a low potential for severe side effects.
The FDA's approval will allow physicians, including those without a medical marijuana license or certificate, to prescribe this medicine the way they would any other. However, CBD as a line of treatment can only be lawfully pursued by patients and caregivers once "all possible treatments (including FDA-approved new and add-on medicines, dietary therapy, devices, and surgery) have been reasonably tried," according to the U.S. Epilepsy Foundation. 
Cannabidiol, in the strengths indicated and approved, has a low potential for causing liver damage. The most common tolerability issues reported during trials included sleepiness, low appetite, and diarrhea, but these presented mostly in patients on very high doses of CBD.
The most recent study to look at CBD and seizures associated with Lennox-Gastaut syndrome was published this year in May.
Researchers looked at the efficacy and safety of CBD for treatment-resistant seizures when it was taken together with conventional antiepileptic medication. The trial was well designed and was considered a so-called “gold standard” study—double-blind and controlled for placebo.
The researchers concluded: "Among children and adults with the Lennox–Gastaut syndrome, the addition of cannabidiol at a dose of 10 mg or 20 mg per kilogram per day to a conventional antiepileptic regimen resulted in greater reductions in the frequency of drop seizures than placebo. Adverse events with cannabidiol included elevated liver aminotransferase concentrations."
Only seven patients from a total of 225 terminated their participation due to side effects. 
Only the fact that it was funded and conducted by the same company that manufactures and distributes Epidiolex can be seen as a drawback. But then, this is not the only clinical evidence supporting CBD for epilepsy, with a better adverse-event profile than pharmaceutical drugs.
In an earlier Lennox-Gastaut and Dravet syndrome study conducted at the Mattel Children's Hospital at UCLA in California, children were given a CBD-enriched cannabis preparation as treatment. The parents were then asked to fill in an online survey with a special focus on efficacy, dosage, and tolerability. In total, 117 parents of children with treatment-resistant epilepsy participated.
The conclusion: "Perceived efficacy and tolerability were similar across etiologic subgroups. Eighty-five percent of all parents reported a reduction in seizure frequency, and 14% reported complete seizure freedom...Reported side effects were far less common during CBD exposure, with the exception of increased appetite (30%). A high proportion of respondents reported improvement in sleep (53%), alertness (71%), and mood (63%) during CBD therapy."
The authors noted that the study methodology was not optimal and that further, appropriately controlled clinical trials are necessary to firmly establish efficacy and safety of CBD for seizures. 
CBD for seizures and a myriad of other applications appear to be well on its way toward full acceptance and regulation by government and other official bodies. The majority of U.S. states allow for the legal use of medical marijuana and its derivatives already, but federally, its use is still illegal. Yet this recent FDA approval remains hugely encouraging for the whole pro-CBD community.