Young people are ending up in hospital after smoking synthetic cannabis.

Auckland City Hospital's emergency department often has one or two such patients a day.

A spokesman says most of the patients are aged between 16 and 21.

The Government has promised to move on the drugs, which have names such as Kronic, Aroma and Dream - but not until next April.

However, last night, Associate Health Minister Peter Dunne said he would instruct officials to "look at what further steps can be taken".

"These figures from the Auckland District Health Board certainly do indicate that there is an issue to be dealt with," Mr Dunne said.

The National Poisons Centre says there has been a sharp increase in the number of calls it receives about the effects of the drugs.

Toxicologist Leo Schep said users of synthetic cannabis were being treated at many emergency departments, including in Dunedin, where the centre is based.

'They're turning up [here]. And we [usually] get nothing in Dunedin ED - you just don't get the recreational drugs you get up north. It's serious."

The poisons centre was receiving about 10 calls a month about synthetic cannabis, Dr Schep said.

"That may not sound like much, but to us it's a big jump."

Symptoms - such as anxiety and increased heart rate - were usually harmless, but the centre had been called by paramedics after a user had had a seizure.

Dr Schep would like to see the products banned, but said there was disagreement about the risks they posed.

Those risks have been highlighted by a North Shore mother who posted a warning to other parents on a Trade Me forum after taking her teenage son to hospital on Tuesday night after he smoked Kronic.

She said the experience was the "worst night of my life ... His heart had accelerated to an alarming rate, and wouldn't stop pounding".

A law change expected to come into effect in April next year will limit where the R18 synthetic cannabis can be sold and how it is advertised.

The Government will also consider a Law Commission recommendation to make firms gain permission before selling synthetic drugs. The would-be seller would have to prove that the drugs were safe.

Such products can now be sold until they are proven harmful.

The Government is to formally respond to the Law Commission report before Parliament rises for the election at the end of November.

Institute of Environmental Science and Research forensic general manager Keith Bedford has said that although little is known about them, the synthetic substances in Kronic appear to pose a low-level of risk.

Dr Bedford said a "moral panic" was fuelling attitudes to ban the products instead of restricting them.

But he said he strongly supported the Law Commission's recommendation.

Dr Schep agreed that very little was known about the long-term or even short-term effects of the drugs, and said he found that alarming.

"Marijuana has been well characterised ... It's been around since the birth of time. Whereas these were created in a lab in the 1980s, for a rat for goodness sake."

He said the attention the products received didn't necessarily match the harm they posed.

"I think part of the attention is because it's so readily accessible. My youngest son, who is 12, could walk into a local dairy and buy it with his pocket money."

While some teenagers would always experiment with drugs, Dr Schep said, it was easier for them to do so when the product was legal.

Western Australia's Health Minister, Kim Hames, announced on Monday that the state would ban synthetic cannabinoids such as Kronic.

Other Australian states are likely to follow.

But Kronic's Albany-based manufacturers have already announced a new "Aussie Gold" formula they claim will still be legal.

A report by New Zealand's Expert Advisory Committee on Drugs noted that when substances are banned, new compounds quickly emerge to take their place.

That seemed to be confirmed by Kronic in a post on its Facebook page: "We've got a few tricks up our sleeves, and you should see our sleeves ... Gandalf would be jealous".

* Auckland City Hospital emergency department often treats one or two synthetic cannabis smokers a day.
* Most patients are aged 16 to 21.
* About 10 calls are made every month to the National Poisons Centre about the products.
* Associate Health Minister Peter Dunne says he will "look at what further steps can be taken".