(CNN) Kratom is an opioid-like substance sought out by users to boost energy and manage pain. It's long been considered a supplement, loosely regulated by the Food and Drug Administration. In August (PDF), the Drug Enforcement Administration outlined plans to move it to the controlled substances list. However, after a public outcry, including letters from members of the House of Representatives and the Senate , the DEA withdrew its intent make it Schedule 1. Instead, it opened a pubic comment period to react to possible scheduling. The public comment period closes at 11:59 p.m. December 1.

Schedule I drugs are considered to have "no currently accepted medical use and a high potential for abuse." Drugs considered Schedule I include LSD, marijuana, heroin and ecstasy.

But what do we know about kratom?

Native to Southeast Asia, the kratom tree's leaves have been used for centuries as an herbal drug by laborers and farmers. Today, kratom leaves are ground into pills and powders, and sold as a dietary supplement. It can be found in head shops and online. It's even made into drinks in some bars

When taken at low dosages, kratom can act like a stimulant, heightening alertness. At higher doses, kratom is a sedative, producing opioid-like effects that dull pain.

-- the active ingredients in kratom -- bind to the opioid receptors in our body, said about as potent as morphine, Boyer said, and "dulls pain very well. ... You can have very, very good analgesia." It has this effect because mitragynine and 7-hydroxymitragynine-- the active ingredients in kratom -- bind to the opioid receptors in our body, said Dr. Ed Boyer , a professor of emergency medicine at the University of Massachusetts Medical School, who has done a handful of studies on the substance. It'sabout as potent as morphine, Boyer said, and "dulls pain very well. ... You can have very, very good analgesia."

But unlike opioid drugs such as hydrocodone or heroin, kratom doesn't appear to slow breathing, Boyer said.

An alternative for pain relief

A growing number of people in the United States have turned to kratom. According to a July report by the Centers for Disease Control and Prevention, calls to poison centers about kratom exposure increased tenfold from 26 in 2010 to 263 in 2015. About 35% of the reported cases involved mixing kratom with other substances, such as benzodiazepines and narcotics.

Some people use kratom for its pain-relieving quality. One of them is Leonard Rodda, who owns a store in Atlanta that sells the herb. He began using the supplement about two years ago, after having side effects from the narcotics he was prescribed after a car accident.

"Before I changed over to kratom, my life was almost suicidal. I couldn't drive. I was sleeping all the time. If I went to a movie, I was asleep within a little while. It wasn't a way to live. I've always been active. I always worked out," Rodda said.

"When I started taking kratom, I noticed some of my old self come back: work out in the yard, ride a bike, you know, that kind of thing. Quality of life is a big thing, and I think kratom has been great for me."

Rodda takes two doses of kratom in the morning and says his pain has disappeared and his life has completely changed. He says that many of his kratom customers are like him: middle-age or older, looking for pain relief.

"It does give you a little euphoria," Rodda said. "Sometimes, it makes you concentrate better. There are some strains that give you a little lift."

A solution for opioid addiction?

Online, there are instructions and testimonials about how to use kratom to withdraw from opioid addiction. It's an increasingly popular use, Boyer said.

"One of the benefits of it is, it treats opioid withdrawal, helps individuals with problematic opioid use, eliminates some of the stigmas," he said.

Typical treatments for opioid addiction, such as methadone and buprenorphine, often require frequent visits to doctors and counselors and dealing with insurance. But kratom does not. You simply can buy it online or at a store.

But Boyer pointed out that the "quick fix" that kratom can appear to be is not a solution for opioid addiction.

"Providing something that you can just walk into a head shop and purchase ... you eliminate getting true professional help," he said.

And there is the risk of becoming addicted to kratom, Boyer said.

Risk of addiction

According to the DEA (PDF), long-term withdrawal symptoms from kratom can include hostility, aggression, emotional changes, runny nose, achy muscles and bones, and jerky movement of the limbs. In some cases, users may experience hallucinations and delusions. However, this is based on a 1975 Thai study of kratom users, some of whom also had a history of opium or heroin use.

Overall, the effects of the plant aren't well understood. There have been a handful of reports of seizures related to kratom use. "It appears in certain individuals ... but it's clearly an uncommon event; otherwise, you would find a lot of reports of it. That's not being seen. It's very sporadic," Boyer said.

According to the DEA, there have been 15 kratom-related deaths worldwide between 2014 and 2016. However, it is unclear whether other drugs were also involved. "What they cannot say is [that the deaths were] caused by kratom. You don't know if kratom caused it," Boyer said.

In addition, because of the loose regulation of kratom, it's hard to determine whether the supplement may have other additives that might contribute to its toxicity. In fact, Boyer cited a case in which someone came into the emergency room because of kratom use, but toxicology reports revealed that what the patient thought had been kratom was actually hydrocodone. "We know it's not just kratom," Boyer said.

As one study cautioned , "the protean blends of herbal products, and potential for contamination with synthetic chemicals, make the risk for opioid-related death a real and unpredictable possibility."

Federal agencies take action

In 2014, the FDA issued an import alert that allowed US Customs agents to detain kratom without a physical examination. "We have identified kratom as a botanical substance that could pose a risk to public health and have the potential for abuse," said Melinda Plaisier, the FDA's associate commissioner for regulatory affairs.

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According to the DEA, between February 2014 and July 2016, nearly 247,000 pounds of kratom were seized.

Up until now, the DEA considered kratom a " drug of concern ." If kratom receives temporary Schedule I distinction, it can be listed for up to three years, when the DEA can then decide to make the designation permanent.

The CDC calls the increase in kratom use in the United States " an emerging public health threat ." But Boyer says there simply isn't enough known to draw any real conclusions about the drug.

For policy makers, he said it is a matter of balancing clinical utility versus risk. "So, are they banning a substance that has potential clinical utility? Possibly. Are they banning a substance that has profound risk to people? Possibly," Boyer said. "I think what I would prefer is to see somebody not ban it but at least do some research to see how bad the risk is or how good the benefit is."