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Everything You Need to Know About K2, the Dangerous Weed Knockoff

“There’s nothing 'natural' about it. They’re just deadly chemicals made in a lab."
Spencer Platt / Getty

K2 has been masquerading as a substitute for weed for the past decade, every since Clemson University chemist John W. Huffman synthesized the compounds as research tools to study cannabinoid receptors. But his recipe has been bastardized in dangerous ways.

In bigger cities—especially ones with a substantial homeless population (the drug is cheap; you can get a hit for two dollars)—K2 has been causing a lot of adverse effects and even killing people. Some of the latest reports have shown that a batch in New York recently had rat poison in it. That might sound bizarre, but because there’s no established recipe for K2, it just is what it is. “Someone was seeking a new kind of high, maybe?” says Amarjot Surdhar, a psychiatrist who deals with substance abuse and addiction at Northwell Health in New York. “In an attempt to diversify some of the drugs people are selling, [k2] dealers or chemists may try to make various combinations of things.” Surdhar echoes something similar to what his peers are suggesting: The poison could tie up liver enzymes that metabolize other drugs, extending their effects. It could also just be malicious intent. What we do know is that K2 is making people sick. So why do people keep taking it?


What exactly is in K2?

Synthetic marijuana, otherwise known as K2 or Spice, is dried plant matter sprayed or coated with man-made hallucinatory substances that are created in an attempt to mimic THC, the psychoactive compound in marijuana. Super fun and reassuring fact if you’ve tried it or are considering trying it: Each bag is a mystery melange of chemicals. “There really is no one ‘main ingredient,’” says William Fantegrossi, psychopharmacologist and K2 researcher at the University of Arkansas for Medical Sciences. There are literally hundreds of synthetic cannabinoid drugs which can be found in these products.” The original compounds—first invented for research rather than to get high—are also totally different from what’s out on the street and online today.

To put it plainly, Huffman’s research got hijacked by dealers who wanted to see if they could imitate the effects of THC, cheaply produce a lot, and go all Frank Lucas in these streets. “It got out of his scientific literature and on to the street,” says Jane Maxwell, a research professor with the Addiction Research Institute at the Steve Hicks School of Social Work at The University of Texas, Austin. “That’s where you get the stories about people spraying it on potpourri and mixing it all up.” Yes, you heard me, potpourri. It gets better.

“You know where the potpourri comes from? Where the cheapest source of dried flowers are?” Maxwell—who’s spent time in the field for the past few years, getting to know everything about K2 culture—asks me. “The dried floral arrangements at cemetaries. People go out and harvest the dry stuff off of that. I’ve seen it happen. There’s large quantities so they use a clean cement mixer, throw the chemicals in there to mix it up.”


Why is K2 called “synthetic" marijuana? Does it provide the same type of high?

This is a loaded question and the short answer is no. The mixture of many different compounds works on the same receptors on the brain as THC, which is why it produces a high, Surdhar tells me. But K2 is way more intense.

Fantegrossi broke down some very complex but enlightening explanations of why. A little context: Drugs exert their actions as a consequence of binding to specific protein targets, or receptors. The ability of a drug to bind to a specific receptor is a measure known as “affinity,” and drugs with strong affinity bind better than those with weaker affinity. All drugs that exhibit efficacy at a specific receptor are known as “agonists” at that receptor. Drugs that induce a stronger response are referred to as “full agonists,” while drugs that only produce weaker responses are referred to as “partial agonists.”

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Synthetic cannabinoids found in K2 exhibit stronger affinity for CB1 receptors (one of two cannabinoid receptors, located in the central and peripheral nervous system) than THC, Fantegrossi says, and once they bind, they function as very high efficacy agonists (whereas THC functions only as a low efficacy, partial agonist). So “no matter how much cannabis you smoke, no matter how high the THC concentration in that plant material, you will simply max out the CB1 stimulation at a level far below what you can get with the synthetic cannabinoids in K2.” This might make people tempted try K2, thinking it’ll be marijuana but stronger. But it’s not just stronger, but way more unpredictable. There may be hallucinatory effects, and it affects each person differently.


Who is buying K2, and why?

a. It’s cheap and b. It can be addictive, so it may not be that people exactly choose to keep taking it. Thirdly, Maxwell says that in the early days of the drug’s street life—2009 and 2010—K2 was appealing to people who were on parole because it got them high and was, unlike most drugs, undetectable in a piss test. It still is pretty hard to detect in a person’s system. Fantegrossi elaborates: “Because the drugs found in these products are chemically distinct from the phytocannabinoids found within marijuana—things like the tetrahydrocannabinols and cannabidiol—they don't "cross-react" in standard urine toxicology screens.” Users are generally in their 20s and 30s and are more often male than female, and for the most part, they’re not in a position to afford more expensive drugs.

Where are people buying K2?

It used to be available at corner stores, in colorful packaging clearly indicating what it was. It’s been a banned substance since 2012, and now tends to come in more covert packaging, Maxwell says, and it’s most often purchased online since store owner aren’t allowed to sell it. It’s marketed as “enhanced” or “natural,” Surdhar says, but “there’s nothing natural about it. They’re just deadly chemicals made in a lab. And it’s very difficult to track things online if people are not declaring the contents, or the contents in it are not illegal.”

What adverse effects does K2 have on the body and how often does this happen?

Neurological side effects of K2 can present as agitation, confusion, dizziness, lack of coordination, sedation, and even seizures, says Tegan Boehmer, scientist and acting Health Studies Chief in CDC’s emergency management, radiation, and chemical branch. “Psychiatric symptoms are hallucinations, psychosis, violent behavior, and suicidal thoughts.” There’s also sometimes, nausea, vomiting, and chest pain, which Surdhar has seen when he’s received patients in the ER. Some of the more serious effects are myocardial infarction (heart attack), tachycardia (fast heart rate), hypertension (high blood pressure), acute kidney injury, and even death.

“The most important thing to know is that the synthetics are absolutely not marijuana,” Fantegrossi says. “Any one of these things can happen the very first time you try one of these products because you don't know what drug you're getting, you don't know how much is in there, and you don't know how your own individual metabolism will handle it. The warnings you see from the CDC and NIH are not scare tactics. Be careful out there.”


There hasn’t been an accurate count of deaths from K2 since the uptick in usage took place within the last few years. Deaths are rare, but Maxwell says there’ve been at least a handful in several states, including her own (Texas). There’ve been a lot of poisonings though.

Maxwell also says that around 20 percent of users report minor side effects that resolve quickly; 40 percent report more moderate ones that are prolonged; and 10 percent have been shown to exhibit symptoms that were life-threatening or resulted in significant residual disability that might be long-term.

How do doctors treat the adverse effects and addiction to K2?

Sometimes K2 users don’t want to get treated at all because they fear legal repercussions or that the doctor will chastise them, Surdhar says, but if they do end up in the ER, doctors provide comfort measures, treat them symptomatically, and have them evaluated for safety issues. Sometimes a patient will need to be medicated because of aggression or similar symptoms. Once the effects are gone, a patient might be kept in the hospital for a couple of days, Surdhar says, “Because many of them have some baseline psychiatric disorder on top of their use.” These things often go hand in hand, he says.

As far as addiction goes, all of my experts express frustration about how to somehow halt the surge in usage. “We are all at our wit’s end with these things. The evolution of this business keeps running ahead of the law enforcement, and the medical and science world,” Surdhar says. He says they’re working on pushing awareness and trying to operate with compassion at this point. “In our society, we have a knee-jerk reaction to anyone who uses any kind of psychoactive substances. Immediately, they’re bad people. From my perspective as a clinician, we’re trying to have a non-judgmental kind of understanding.”

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