Drugs known as K2 or Spice, often sold as "safe" or "legal" versions of marijuana, are none of those things, a research review concludes.
These synthetic cannabinoids (SCBs) are not detectable with standard drug screening for the active substance in marijuana because they are very different, and potentially dangerous, molecules, the study team writes in Trends in Pharmacological Sciences.
"Synthetic cannabinoids produce a number of adverse effects such as neurological, gastrointestinal, cardiovascular, and renal toxicities as well as tolerance, dependence, and even withdrawal," lead author Benjamin Ford from the University of Arkansas for Medical Sciences in Little Rock said.
Evidence of K2 and Spice use in the United States was first reported in 2009, Ford and his colleagues write, but it wasn't until late 2010 that the National Forensic Laboratory Information System reported tremendous spikes in K2 and Spice product usage.
"Alarmingly, there have been over 20 deaths reported between 2011 and 2014 due to some of these toxicities," Ford told Reuters Health by email.
A major issue regarding acute toxicities of SCBs concerns the poor and inconsistent quality control of synthetic cannabinoids in these products, Ford said.
"It is common for a single K2 or Spice product to contain between three to five different synthetic cannabinoid compounds at arbitrary, and sometimes dangerous, doses," he said.
Ford and his colleagues reviewed existing studies of the chemical structure of these compounds, how they work in the brain, how they affect animals in experiments, and the types of side effects seen among human users.
Ford concludes that terms like "synthetic marijuana" or "synthetic pot" are very misleading descriptions. They suggest that K2 and Spice products contain marijuana-like compounds and produce effects similar to those of marijuana, he said. But, the SCBs are much more potent than regular marijuana and sometimes cause more intense reactions.
It's important to note that there is very little crossover between the adverse effects observed with synthetic cannabinoids and marijuana, he added.
"The problem is that people are abusing these new synthetic cannabinoid receptor agonists because a lot of them don't show up on the urine tox screen," Dr. Rana Biary, an emergency physician at NYU Langone Medical Center in New York, told Reuters Health.
"So it's a way to bypass any form of drug screen monitoring, and so a lot of people who are regularly having their own drug screens sent on might be using this in lieu of marijuana," said Biary, who wasn't involved in the review.
Biary noted that the earliest synthetic cannabinoids were chemically designed to look just like THC, the psychoactive substance in marijuana, and were studied as a way to reduce cancer-induced vomiting.
"But what ended up happening is there was an unexpected side effect where they found that people were having different effects, and so they then started to create different molecules that actually no longer resemble THC," she said.
"The reason that we're kind of getting concerned about synthetic cannabinoids now is that first of all, the molecules are changing so quickly that we actually don't really know what is in the bag that people are selling," Biary said.
"As soon as we start to regulate one, there's already several that are down the pipeline of new synthetic cannabinoids that are available," she said.
One problem in with overuse symptoms is that there's no consistent presentation as far as symptoms, Biary added.
"So with one batch, patients might come in wildly agitated, screaming, needing to be restrained, needing large amounts of medication to sedate them, while the next batch, they're coming in not breathing so well, their blood pressures might be low," she said. "So part of the problem is the presentations are so unpredictable, and you can't really say you know if someone overdosed on, or is using, a synthetic cannabinoid."