Vomiting, drowsiness, chest pain, palpitations and dissociation from reality are some of the symptoms associated with synthetic cannabis such as Kronic, a Dunedin-based toxicologist says.
Leo Schep, of the National Poisons Centre, said there had been a "big spike" in calls concerning synthetic cannabinoids - plant matter that had been sprayed.
Of most concern was the clinical effect on people: "We just don't know the long-term effects".
"We just don't know what the hell is going on."
The centre had received calls from people who "feel like death has just walked up" and from emergency departments wondering what the product contained, Dr Schep said .
"This is a re-run of BZP."
The use of BZP (or Benzylpiperazine), from its introduction in 2000 to its being banned eight years later, was of public health concern, and synthetic cannabis should be treated no differently, he said.
Dr Schep said he was writing an in-depth review on synthetic cannabis because there was not enough information on the product.
"We know the short-term clinical effects, but as for long-term effects, we have no idea."
Community Alcohol and Drug Service (CADS) medical specialist Dr Gavin Cape said too little was known about its effects, toxicity, and addictiveness.
"The problem with making [Kronic] illegal is that there are thousands of chemicals out there, and also you drive it underground."
Cost-wise, it was roughly on a par with cannabis, without the risk of a criminal conviction.
If cannabis was legal, it was unlikely the substitutes would "get a look in".
Dr Cape was concerned about a lack of information on product packaging.
`There's very little information on the actual product.""It doesn't actually say what it is.
"It says it contains lots of different herbs. It might contain those herbs, but the active ingredient is a chemical that's been synthesised in a laboratory that's probably sprayed on to the various herbs."
CADS had had no referrals for Kronic use but Dr Cape said he had received mixed reviews from cannabis users who had experimented with it.
"If you do use it, you have to be pretty careful with it, is my understanding.
"It seems to affect different people in different ways, so there isn't one standard effect that it has.
"Some people say that it's very strong and lasts a long time and they feel incapable of doing many usual things ... a worry would be if you drove a vehicle - that probably is not a good idea."
Others described it as a "pale imitation" of cannabis, he said.
