Every week, the Nuance will go beyond the basics, offering a deep and researched look at the latest science and expert insights on a buzzed-about health topic.

In late June, the U.S. Food and Drug Administration approved a new drug to treat epileptic seizures. That drug, Epidiolex, gives patients a concentrated dose of cannabidiol (CBD), an organic chemical compound derived from the cannabis plant. It’s the first time the FDA has approved a prescription drug that uses an active compound found in marijuana.

It’s hard to overstate the importance of this FDA decision.

Roughly one in seven epilepsy patients is a child, according to the CDC, and CBD has long been known to relieve epileptic seizures. Some parents of children with epilepsy have gone so far as to travel to states where cannabis products are legal to procure CBD oil and bring it back, often illegally, to help their kids. Online epilepsy communities are packed with heart-wrenching testimonials about the benefits of these products.

Now, parents and patients won’t have to travel so far afield to get the medicine — Epidiolex will make CBD accessible everywhere.

For now, the drug is approved only for the treatment of seizures in patients with certain rare forms of epilepsy. But experts say it’s likely to have wide-ranging benefits — and many doctors will likely prescribe it off-label, which is legal in the United States for approved drugs.

“I think it’s going to have pretty broad efficacy for other types [of epilepsy],” says Elizabeth Thiele, MD, PhD, a professor of neurology and director of the Pediatric Epilepsy Program at Massachusetts General Hospital.

It’s hard to overstate the importance of this FDA decision.

It’s at the discretion of insurers whether to cover off-label applications of the drug, but Thiele suspects some doctors will be willing to write the script. “The need for [seizure drugs] in pediatrics is huge, and we’ve been using drugs off-label to treat pediatric epilepsy my whole career,” she says.

Doctors still don’t know conclusively how it works, but its use is not without precedent.

“The cannabis plant itself has been used for the treatment of epilepsy for a very long time,” says Jerzy Szaflarski, MD, PhD, director of the University of Alabama at Birmingham Epilepsy Center and author of one of the primary CBD studies that helped inform the FDA’s ruling. How long? Roughly 2,000 years, according to research that tracks the cannabis-epilepsy connection all the way back to ancient Mesopotamia. Szaflarski says the cannabis plant contains more than 500 different active and inactive compounds, and CBD is just one of them. What makes these compounds special is that they have the ability to act on the human nervous system’s endocannabinoid system.

The specific functions and operations of that system are opaque, but Szaflarski says it has been linked to the regulation of mood, sleep, pain, appetite, and other essential processes. By mimicking some of the human body’s neurochemicals, CBD and other cannabis compounds — including THC, the chemical that causes the “high” associated with marijuana use — can act on the endocannabinoid system both directly or indirectly. There’s also some evidence that CBD could relieve pain, anxiety, and other mental and physical ailments, says Igor Grant, MD, chair of the Department of Psychiatry at the University of California, San Diego School of Medicine.

Orrin Devinsky, MD, is director of the Comprehensive Epilepsy Center at New York University Langone Health. He says two specific nervous system receptors seem to be influenced by CBD. “But that is not proven,” Devinsky says.

“The mechanism of action is not a real sticking point for most clinicians or their patients,” Thiele says. “There are many medications we use where we don’t understand why it works.” The important thing, she says, is that epilepsy patients and their families now have a well-regulated, rigorously tested CBD treatment.

Asked about commercial CBD products — the oils and balms and other products sold in some states — Thiele’s endorsements are muted. “I am not as enthusiastic about going to a dispensary and getting CBD oil,” she says. “In trials, we’ve been looking at a purified CBD compound, not an extract of cannabis.” Thiele says these commercial products are mostly unregulated, so users have to rely on the quality assurances of the companies that manufacture and sell them. “I know many of my patients are using those, but I’d prefer a product that’s gone through the vigorous FDA approval process, especially for children who are growing and developing,” she says.

“The mechanism of action is not a real sticking point for most clinicians or their patients.”

Szaflarski mentions one popular commercial product: a CBD formulation called Charlotte’s Web that famously helped relieve the incessant grand mal seizures afflicting a young girl named Charlotte. “I do have patients who obtain CBD like this out of state, and they say they do better,” Szaflarski says. But like Thiele, he has reservations. “The concentrations in these products are only approximate, and I don’t know how well they’re tracked,” he says.

While prudent, his and Thiele’s concerns may seem like quibbles to the parents of children who are suffering. They may also seem somewhat unjust, considering that commercial and illegal CBD products were, for many years, the only options for a parent or patient — and undoubtedly helped guide medical science toward an FDA-approved drug like Epidiolex.

For many, that debate is moot. A tightly regulated, FDA-approved prescription CBD drug is now available. The era when parents and patients had to drive to another state in search of relief is coming to a close.