The Drug Foundation is urging people to smoke real weed instead of playing Russian roulette with synthetic cannabis.
The call comes after video showing three stoned young men was uploaded to Facebook, one of whom is frothing at the mouth. That video came just weeks after a clip of a zombie-like young woman made headlines.
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Drug Foundation director Ross Bell says things are getting dire.
"We've got a situation now where I would recommend if people are going to choose to smoke something, to smoke natural cannabis over this synthetic stuff," he told Newshub.
The video of the young men in the park has been viewed more than 200,000 times in less than two days.
Massey University senior drug researcher Chris Wilkins says it's difficult to know how widespread the problem is because synthetic high users have no idea what they're actually consuming.
"They're often sold something they're told is ecstasy or LSD, or just natural cannabis, and actually it's one of these various dozens of compounds."
Youth are particularly at risk.
"They're more likely to believe just because it comes in a packet and it's got fancy writing on it that somehow it's safer, it's been tested," says Prof Wilkins. "That is not the case at all."
"I think the thing that we should be doing is giving really good, honest factual information about what is actually out on New Zealand's black market right now," says Mr Bell. "It is a smorgasbord of new chemicals."
Prof Wilkins says the United Nations is monitoring more than 600 different compounds used in synthetic highs, most of which are not subject to any international drug treaties, nor tested.
"Some of these compounds are toxic, they haven't been tested on anyone. They're novel compounds. And manufacturing is variable - even within a batch, you get different potencies of the compound, or you get different compounds or a mix of compounds. It's Russian roulette."
Aside from alcohol, psychoactive substances are largely banned in New Zealand, no matter what they contain. But Prof Wilkins says Customs has a hard time stopping them at the border.
"These literally just come in as powders in bulk, so you need to be able to forensically test those to identify what compound it is and stop it. It's a big challenge."
Mr Bell says it's time for the Government to treat cannabis as a health issue, not a criminal one.
"We have to be pragmatic. In lieu of anything else happening, it is ridiculous that people are choosing to smoke these very dangerous chemicals."