For a nation in the grips of an opioid epidemic, Scott Carpenter's story sounds familiar: He took prescription painkillers for chronic knee pain, and the pills became an on-again, off-again habit.

He broke the cycle four months ago when he started taking a herbal supplement called kratom to control his cravings.

“It was a game-changer,” said the 51-year-old Denton man who works in construction. “I took it and was thinking to myself, this is how normal people feel.”

The Southeast Asian plant derivative, which has been used for generations by people overseas for pain, and mood disorders, and to boost energy, is gaining a following in the United States. It can also help wean someone off addictive opioids, some say. But imports of capsules, teas and other kratom products will be cut off at the end of September, when a U.S. Drug Enforcement Administration ban of the plant's active compounds goes into effect.

The DEA says the goal of the ban is avoiding “an imminent hazard to public safety,” as agency officials figure out how to regulate what they consider an increasingly popular recreational drug.

The DEA plans to “schedule” kratom in its top tier of controlled drugs, which includes heroin, LSD and marijuana. That's a category reserved for compounds with no accepted medical use, a high potential for abuse and a lack of safety, said Todd Edwards, a spokesman for the DEA's Baltimore District Office.

Agency officials say kratom produces “opioid-like effects” and is often marketed as a legal alternative to controlled substances. The DEA reports that law enforcement nationwide has seized more of the supplement in the first half of 2016 than in any previous year, accounting for millions of doses illegally marketed as treatments for which they haven't been approved.

While the agency considers kratom dangerous, it is also concerned about the dubious purity and consistency of the derivative being used; herbal supplements are not government-regulated. There have been more than 660 calls to U.S. poison centers between 2010 and 2015 linked to kratom, up from two calls between 2000 and 2005, according to the U.S. Centers for Disease Control and Prevention.

Edwards said the agency has not been involved in any Baltimore area cases, and Baltimore health officials say they've not come across kratom much. The state Department of Health and Mental Hygiene, though, said there have been five kratom-related deaths in the past two years.

That's a fraction of the number of overdose deaths from opioids. In Maryland last year, there were 748 deaths related to heroin, 340 attributed to fentanyl and 351 related to prescription painkillers.

Authorities nonetheless see potential peril from Kratom.

“The Department of Health and Mental Hygiene urges Marylanders to avoid taking substances for the purpose of experiencing a high,” said Dr. Howard Haft, deputy secretary for public health. “At the most extreme range, we see such opioids as heroin and fentanyl contributing to fatal overdoses on an epidemic scale.”

There have also been instances of fatal overdoses related to synthetic substances, he said, and now kratom is posing “a threat to life if used.”

Kratom has been on a federal watch list for years, and a half-dozen states already have banned it, according to the American Kratom Association. Users have been able to buy the supplement online, however.

The impending ban frustrates kratom users; almost 133,000 have signed a WhiteHouse.gov petition to keep it legal.

Users like Carpenter say alternative over-the-counter and prescription medications were not only less effective than kratom for pain and addiction but carried side effects. Carpenter said kratom also improved his anxiety and mood, allowing the single father of a 10-year-old boy to get through his home and work day more even-tempered and clear-headed.

Such testimonials have proliferated online as the once “underground” product has become more widely used in the United States over the last 15 to 20 years, said Walter C. Prozialeck, chairman of the department of pharmacology at Midwestern University.

Prozialeck published a review of kratom studies in 2012 and found research into the plant's power as a pain reducer and addiction treatment promising, though still in the beginning stages.

He called taking kratom off the market unwarranted, since much of the danger is not likely from the plant but from other drugs combined with it by users or unscrupulous dealers.

“There have been some really bad drugs of abuse the DEA has banned, like bath salts,” he said. “They caused a high but also had a tendency to cause psychiatric effects in some individuals. There was also synthetic marijuana, which wasn't marijuana but had an effect similar to THC, the active constituent of marijuana. In each of those cases there was more evidence the drugs were harmful. It's less clear with kratom.”

Andrew Kruegel, an associate research scientist at Columbia University who studies kratom, said its long-term health effects still need to be explored. But he sees the most promise in developing kratom into new types of pain relievers, without some of the dangers posed by traditional opioid-based prescription painkillers.

Kratom's active compounds — mitragynine and 7-hydroxymitragynine — activate the same opioid receptors in the brain that the prescription painkillers do but in unique ways that avoid some of the side effects, he said. Kratom is less likely to cause dependence or respiratory depression, which is what kills people who overdose.

The compounds in kratom “are very exciting from the research perspective because they provide an opportunity to address the opioid overdose epidemic that is currently sweeping our nation through the development of new, safer drugs for pain,” Kruegel said.

His research team will apply for a license from the DEA to continue kratom research during the ban, but Kruegel said he's concerned that the ban on imports will make obtaining plant material difficult.

He's also concerned that the DEA's move will stigmatize kratom, further complicating drug development. “I do not think there is clear evidence at present that kratom use represents an imminent public health hazard, which would warrant emergency placement on Schedule 1,” he said. “The scientific literature in cells and animals, and anecdotal evidence in humans, suggests that kratom may be safe, but more research is needed before making an informed regulatory decision.”

Signs warning customers of the ban are already going up in local smoke shops, with one Baltimore County store owner lamenting that kratom — sold for $1 a capsule — now makes up more than 40 percent of business.

Others say they aren't sure what they'll do when kratom is no longer available.

Michelle Meadows, a 28-year-old Richmond, Va., restaurant manager and student, said kratom helped her kick her longtime heroin addiction last year and she still takes it to stave off cravings.

She first bought kratom online in 2014 to get high, but “it had little recreational appeal,” she said, “and this comes from the same woman who would ingest multiple boxes of cough medicine and inhale carbon dioxide from soda bottles as a teenager.”

Meadows said after a three-week heroin binge last spring, she decided she'd had enough and decided to try her leftover kratom stash to treat herself. She took it on a regular schedule to avoid the pain and discomfort of detoxification, eventually weaning herself down to once a week.

The supplement gives her a lift in energy and mood, similar to caffeinated coffee or tea, she said.

“I have developed a spiritual connection to this plant,” she said. “It has allowed me to become a productive member of society. It has allowed me to be the best mother, wife and student that I can be. It has given me my life back”

meredith.cohn@baltsun.com