The Food and Drug Administration is cracking down on several companies selling products advertised as containing cannabidiol (CBD), a compound in marijuana widely used without FDA approval to treat epilepsy and other conditions – and some medical pot activists are pleased to hear it.

In late February, the federal agency sent letters to seven companies that market CBD products to treat health conditions, five of them for humans and two for pets, warning their products are not “generally recognized as safe and effective“ and that the companies are engaging in illegal interstate commerce.

Marijuana is a Schedule I drug under the Controlled Substances Act, which means under federal law it has no accepted medical value. CBD, however, does not produce a high and research into the compound is on the upswing as parents of epileptic children and others flee to states that allow its use.

Although now accessible in most states – as 23 allow medical marijuana and a dozen others, many in the Deep South, allow just CBD oil – the FDA has not approved any CBD medicines and the products cannot be marketed for treatment of health conditions.

“To date, the FDA has not approved any drug product containing cannabidiol, for any indication, meaning none of these products have been determined by FDA to be safe or effective for their intended indications,” agency spokesman Jeff Ventura tells U.S. News.

“FDA has grown concerned at the proliferation of therapeutic claims being made about an increasing number of products, for sale in all 50 states, purporting to contain cannabidiol,” he says. “The marketing and promotional materials for many of these products indicate they are intended for the use in the diagnosis, cure, mitigation, treatment, or prevention of diseases, including, for example: cancer, various infections, psychiatric disorders, multiple sclerosis, arthritis and diabetes.”

Ventura says the FDA “has not issued guidance or an opinion on these kinds of products, [but] the agency reserves the right to take action when appropriate to preserve and protect the public health.”

Kevin Sabet, a former presidential drug policy adviser who now leads the anti-marijuana legalization group Smart Approaches to Marijuana, celebrated the FDA crackdown in a Wednesday email to supporters. “Let's hope this is a sign of more intervention to come,” he wrote.

Perhaps surprisingly, some pro-CBD activists hold the same view, seeing the crackdown as a good thing for patients and a way to weed out bad actors.

The FDA supplemented its letters with publicly released lab results showing levels of CBD in contested products. Some items, the results showed, had CBD concentrations lower than advertised.

“I’m extremely encouraged that they’re taking a look at this from the consumer point of view of safety,” says Paige Figi, founder of the Coalition for Access Now. “That’s exactly what I stand for and what I want.”

Figi’s daughter Charlotte suffers from Dravet syndrome, a rare and debilitating form of epilepsy that CBD appears to treat effectively. A high-CBD strain of cannabis called Charlotte’s Web is named for her.

The company that produces Charlotte’s Web-branded items in Colorado and California uses third-party lab testing to ensure quality, Figi says.

“They’re cracking down on quality, which is extremely important, and I’m very happy – I couldn’t be more pleased,” Figi says. She says she's glad the FDA outed companies misrepresenting their products and agrees with the FDA that health claims should currently be avoided by companies.

“It’s nerve-racking and frustrating to watch companies act this way,” she says. “I don’t think people should be making claims until we have proven data.”

Kris Hermes, a spokesman for the pro-medical marijuana group Americans for Safe Access, says CBD-producing companies likely can avoid FDA warning letters quite easily.

“Threatening letters from the FDA are not as likely to target medical marijuana companies that: a) do not engage in interstate commerce and only sell their products within the states that have legalized medical marijuana, and b) do not make claims as to proven efficacy without FDA approval,” Hermes says in an email.

Hermes says his advocacy group would be concerned if the FDA crackdown prevents CBD from reaching patients, but notes his group has not tested the contested products. Product reliability is increasingly important, he says, and Americans for Safe Access has set up a third-party certification program to help customers buy products with confidence.

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The FDA currently allows some research into CBD, giving fast-track status last year to a CBD medicine that may one day treat Dravet syndrome and fast-track approval for clinical trials of a drug using both CBD and THC – the marijuana compound that produces a high – for pain treatment for cancer patients.