U.S. health agencies are targeting a threat to Americans that is readily available nationwide.7-hydroxymitragynine, also known as 7-OH, is a concentrated form of kratom, a plant-derived substance that has been commonly used for pain relief and as a stimulant.The concentrated byproduct has been linked to opioid receptors in the body, triggering the potential for abuse and various drug-related symptoms.HEALTH OFFICIALS WARN OF DANGEROUS SUBSTANCE AVAILABLE IN STORES ACROSS THE NATIONThe substance, which is considered a "synthetic opioid," has been bottled into drinks, powders and tablets that are sold at vape shops, gas stations and other stores across the country.An uptick in 7-OH-related medical events has led the Department of Health and Human Services (HHS) and the Food and Drug Administration (FDA) to crack down on sellers of these products.In a Tuesday press release, the HHS announced that the FDA is recommending a scheduling action to control these products under the Controlled Substances Act (CSA).FDA Commissioner Marty Makary, M.D., M.P.H., wrote in a statement that vape stores are "popping up in every neighborhood in America, and many are selling addictive products like concentrated 7-OH." AMID KRATOM OVERDOSE CLAIMS, GROUPS CALL FOR REGULATION, BETTER TESTING OF DRUG"After the last wave of the opioid epidemic, we cannot get caught flat-footed again," he said. "7-OH is an opioid that can be more potent than morphine. We need regulation and public education to prevent another wave of the opioid epidemic."There are no FDA-approved 7-OH drugs, according to the health agency. It is not lawful in dietary supplements, nor can it be lawfully added to conventional foods.Kratom is derived from the leaves of a tree (Mitragyna speciosa) found in regions of Southeast Asia, such as Malaysia and Thailand, according to Lori Karan, M.D., professor of internal and preventive medicine at Loma Linda University in Loma Linda, California, who previously spoke to Fox News Digital.The leaves of the tree contain more than 40 different active compounds, with the most prevalent being mitragynine, 7-hydroxymitragynine and speciofoline. The plant is thought to have dual properties. It produces a stimulant effect at low doses and an opioid-like, analgesic effect when taken in higher amounts, according to Dr. Richard Clark, medical director of the San Diego division of the California Poison Control System."It has activity at opioid receptors in the brain, like opioid analgesics, and for that reason has been used as either a substitute for opioid analgesics or a tool to improve symptoms of opioid withdrawal," Clark previously told Fox News Digital.Americans most commonly use kratom for self-treatment of chronic pain and to help battle opioid withdrawal symptoms, he added.When isolated in its concentrated state, 7-OH, the active metabolite present in the kratom plant, becomes a highly potent analgesic.7-OH can be more potent than morphine, leading to the potential for abuse and drug-related symptoms like dependence and withdrawal, according to the HHS.While vendors may advertise kratom as safe and "all-natural," the composition can vary widely and may not accurately reflect the product labeling, experts caution.It’s uncommon for kratom to cause major toxic effects, but when people ingest large amounts or combine it with other drugs, they may experience hallucinogenic reactions, convulsions, coma and, in rare cases, death, Clark warned.CLICK HERE TO SIGN UP FOR OUR HEALTH NEWSLETTER"There is also a potential for individuals to develop dependence and withdrawal with heavy kratom use," he said.Other side effects may include nausea, dizziness, confusion and tremors, according to Karan.The FDA and HHS announced a call to action against 7-OH products in a press conference on Tuesday, where Robert F. Kennedy Jr. described its growing availability and the weight of addiction on the American people."They’re putting [vape shops] around schools, they’re putting them in our poorest neighborhoods, and now they’re putting them in every gas station," the HHS secretary said.For more Health articles, visit www.foxnews.com/health"They’re marketed for children. They’re gummy bears, they’re bright colors, they’re candy-flavored. This is really a sinister, sinister industry."During the same press conference, Makary noted that there is no intention for the agencies to deem pure kratom as "safe" for use at this time.Shiv Sudhakar contributed to this report.