Despite dire warnings about the dangers of synthetic cannabinoids, popularly known by names such as K2, Spice, Black Mamba and Kronic, they continue to grow in popularity. Just yesterday, 33 people were rushed to the hospital in Brooklyn, N.Y. with symptoms that suggested an overdose on the drugs, according to an NBC4 New York report. The city’s health department told the station that there have been more than 6,000 K2-related emergency room visits and two confirmed deaths in New York City since 2015. In January, the American Association of Poison Control Centers listed 1,462 exposures.

To get a better understanding of what K2 is and why the drug is so dangerous, NBC News spoke with Marilyn A. Huestis, a professor at the University of Maryland School of Medicine in Baltimore and former chief of chemistry and drug metabolism at the National Institute on Drug Abuse.

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Q: What exactly is K2?

A: These are synthetic compounds that bind to the same receptor in the body and brain as THC, the most psychoactive ingredient in [marijuana]. In fact, they can have really different structures from THC. The first synthetic cannabinoids were actually produced legitimately as tools for us to investigate the pharmacology of the endogenous cannabinoid system. This system is important for critical functions such as temperature control, hunger and reproduction. It also plays very important roles in the brain for executive function, which is what we use to take in information from the environment, evaluate it, and determine a course of action. The researchers who figured out how make these synthetics published their findings in scientific journals and illicit manufacturers learned from those articles.

Q: So, if the drugs just mimic compounds that are not only found in marijuana, but are also naturally occurring in the body, what’s the problem?

A: People are dying all the time from synthetic cannabinoids. They can be up to 100 times as potent as the THC in cannabis. Though this is a natural system in the body, marijuana or cannabinoids basically hijack the system and take over.

Q: Just how dangerous are these compounds — can they actually kill you?

We have learned that they can not only lead to death, but we have seen histories of kidney damage. They can destroy the kidneys so people may die or need to have dialysis and/or transplants. They can cause cardiovascular effects and can bring on heart attacks and strokes in the brain.

Q: What worries you most about these drugs?

A: It’s frightening. I have studied drugs my whole life and what is so frightening is that so many young people are using these compounds. This is already a known problem with cannabis. We know that if you start before age 17 and you use it frequently, not occasionally, it affects the brain in a way in which the nerves in the brain connect during brain development. So it can reduce IQ and can permanently change the brain, which isn’t fully developed until the end of one's 20s.