Originally Published: 09 AUG 22 03:01 ET

By Sandee LaMotte, CNN

(CNN) -- There's nothing nice or dreamy about synthetic weed, sold under such catchy names as AK-47, K2, Spice, Scoobie Snacks, Mr. Nice Guy and 24-Karat Dream.

Sometimes packaged as e-juice for vaping or as edibles, most synthetic cannabinoids are sold as dried plant materials sprayed with acetone, embalming fluid or other solvents laced with lab-made psychoactive substances.

Between 2010 and 2015, synthetic cannabis poisonings were on the rise, according to the ToxIC Case Registry, with more than 42,000 cases of toxic exposure reported during that time. However, those numbers may now be declining in states in which the use of recreational marijuana is permitted, said Tracy Klein, assistant director for the Center for Cannabis Policy, Research and Outreach at Washington State University in Vancouver, Washington.

She's the lead author of a study that found calls to poison centers about synthetic cannabinoid fell by more than a third between 2016 and 2019 in states that have legalized marijuana for recreational use.

"These products are made in a powdered format and could be sprayed on or added to something that looks exactly like natural cannabis. So, in a party situation, I could see that someone could use this unintentionally," said Klein, who is also an associate professor in the WSU College of Nursing.

However, people may also use synthetic cannabinoids "to attempt to avoid positive drug screens performed as a condition of employment, in substance abuse treatment programs, or in the criminal justice system," according to the US Centers for Disease Control and Prevention.

A deadly problem

Marijuana copycats have sent thousands of people to emergency rooms over the past decade. Some have even died, including a 17-year-old boy "who suffered a cardiac arrest after reportedly taking a single 'hit' of K2/Spice," according to the CDC.

There's no way to know which synthetic cannabinoids are actually in the purchased product or what else might be in the solvents used to soak the dried plants, experts say.

In April 2018 in Illinois, 153 people fell ill and four died after using synthetic cannabinoids laced with rat poison. Later that year in New Haven, Connecticut, a version of K2 sickened 95 people in two days. They experienced symptoms such as nausea, vomiting, lethargy and a loss of consciousness.

Officially known as "synthetic cannabinoid receptor agonists," these artificial products are different from synthetically made cannabis products that have a medical use, Klein said.

"They don't show up on regular drug tests," she said, "nor does the body recognize them in any way that has positive effects."

The study, published Tuesday in the Journal of Clinical Toxicology, analyzed data from the National Poison Data System between 2016 and 2019. Researchers found there were 7,600 calls related to synthetic cannabinoid use during those three years. About 65% of the calls to poisoning centers were for situations that required medical attention and 61 people died.

Over half of those calls (56%) occurred in states with restrictive cannabis policies, the study found. Closer to a third (38.6%) occurred in states that allow medicinal use and 5.5% occurred in "permissive" states, where recreational use is legal, according to the study.

How synthetic cannabinoids work

Synthetic cannabinoids were first developed in the 1980s as a way to study how tetrahydrocannabinol or THC, the psychoactive ingredient in cannabis, impacted the brain to produce a high, the CDC said.

"One particular synthetic cannabis was designed by a pharmaceutical company as a potential drug to ease pain," Klein said. "It was found to be so strong and so powerful, and have so many side effects, that it was not pursued."

Today synthetics are mostly produced overseas and shipped to the United States. In fact, the first shipment "recognized to contain synthetic cannabinoids was seized at a U.S. border in 2008," according to the CDC.

"It's not just a US problem. This has become an international problem," said Klein, pointing to data that lists at least 320 different synthetic cannabinoids sold on the illegal market as of February 2022.

"And those are just the ones that have been reported and identified," she added.

While not the same as weed, synthetics do work on the same cannabinoid receptors as THC, but can be up to 100 times more potent because of the way they bind with receptors in the brain, Klein said.

Exposure can cause mild to severe neurologic reactions, such as agitation and depression of the central nervous system, even to the point of coma. Other symptoms include "sleepiness, irritability, confusion, dizziness, incoordination, inability to concentrate, stroke, and seizures," the CDC noted.

Psychiatric symptoms include "hallucinations, delusions, psychosis, violent behavior, and suicidal thoughts," the agency said. "Other physical signs and symptoms, including tachypnea, tachycardia, hypertension, severe nausea and vomiting, chest pain and heart attack, rhabdomyolysis (breakdown of damaged muscle), kidney failure, and death."

There is no antidote for synthetic cannabinoid poisoning and long-term effects are unknown, the CDC stated. Treatment is supportive, by using intravenous fluids, oxygen, and other airway protection and medications for agitation and combativeness.