Authorities fight to control 'legal highs' but drug-makers have ways of staying one step ahead of the law.
Staff at Middlemore Hospital's emergency department were shocked by the violent seizures and hallucinations in people thought to have taken pills known as "red rockets".
Some users were so aggressive that they required sedation. Six people were treated in one weekend.
The pills are examples of the types of designer drugs available to young people.
They aim to mimic the effects of MDMA, the traditional ingredient of Ecstasy, but use different compounds which are often not covered by laws.
Symptoms similar to those at Middlemore were seen when six schoolgirls, the youngest aged 13, were taken to Waikato Hospital after taking pink pills at school in November last year.
One of the girls stole the pink pills from her mother's handbag and told her Fairfield College friends they were Ecstasy.
The pills were BZP, formerly a legal high but now a Class C drug, which led the girls to act aggressively in the hospital emergency department - behaviour not normally consistent with genuine Ecstasy.
And two 19-year-old aspiring soldiers, admitted planning to sell hundreds of Ecstasy tablets to their military friends for a New Year's Eve party.
George Steele and Shane McHaffie were caught last year with nearly 210 pills, a "big order" from their mates, including other army cadets who had given them money to buy the drugs.
The pills were not Ecstasy but 4-MEC.
Research shows these are far from isolated cases and follow the trend in Europe and the United States, according to the most recent Illicit Drug Monitoring System findings released in October.
Frequent drug users are often quick to switch to new drugs and this means they are well placed to comment on the emergence of new synthetic drugs, says the Massey University research paper led by Dr Chris Wilkins.
The annual study of 372 frequent drug users showed the proportion who noticed a new drug available increased from 9 per cent to 34 per cent between 2008 and 2011.
A total of 39 per cent mentioned "Ecstasy type" pills as the new drugs they had seen last year.
Often these drugs are not covered by laws, so they can be sold as legal highs.
"The paucity of research of the health risks of these compounds, and the fact users are unfamiliar with them, mean they can pose unpredictable and unknown harm."
Of those who noticed "new" drug users, 35 per cent said they had seen more young people taking drugs.
A worldwide shortage of MDMA means other synthetic compounds are being used, but the pills are still marketed as the genuine product.
These Ecstasy analogues are designed to be similar in chemical structure, but not identical, to controlled substances like MDMA so they can be sold as legal highs.
As soon as one analogue is identified and outlawed, the manufacturers tweak the design to stay one step ahead of the lawmakers.
The number of new psychoactive substances identified by the European Monitoring Centre for Drugs and Drug Addiction has rocketed from 13 in 2008, to 57 this year.
The annual EU drugs report, issued last week, says the boom has been driven by online retailers and most of the psychoactive substances sold as legal highs are made in China.
Inquiries by the Herald have found one manufacturer in China, CEC Chemicals, has been linked with the arrest of 10 people in New Zealand.
The company's website has a long list of designer drug compounds which can be ordered online.
Chief executive Eric Chang did not respond to Herald messages. But in emails to British journalists who posed as potential buyers in 2010, he promised to supply "new legal stuff for the UK".
"It falls outside all laws currently regarding research chemicals ... sorry, we cannot disclose the ingredient now. This is our technical know-how," the Daily Mail quoted Mr Chang as saying.
"It can't possibly be banned yet because it was only invented a few months ago."
Mr Chang has been named in court hearings in New Zealand, in which police say a covert inquiry has uncovered evidence of a syndicate importing and distributing hundreds of thousands of pills.
Drugs identified include compounds which the police say are "substantially similar" to Ecstasy and can therefore be considered analogues and Class C controlled substances.
But defence lawyer Ron Mansfield, who is representing several of those accused of involvement in the syndicate, has told the court that the legal definition of an analogue is unclear.
He said none of the drugs found was specifically listed under the Misuse of Drugs Act and the police charges will be defended.
"There is no [legal] authority as to what is and isn't an analogue," said Mr Mansfield.
"This case will turn on whether the substances are, in fact, analogues and could therefore be defined as a Class C controlled drug."
He said one of his clients sought chemical and legal advice before embarking on his "legal high" enterprise.
Once overseas experts were engaged and ESR methods analysed, Mr Mansfield said the error would become apparent - a defence which he has made no secret of to the police.
The case has been described by one judge as the "battleground for the legal high industry".
But even if the defence is successful, the victory will be short-lived.
Legal high substances are to be targeted by new legislation pushed by Associate Health Minister Peter Dunne after a Law Commission report highlighted the loopholes.
The Ministry of Health says current legislation has proved ineffective in dealing with the rapid growth in new psychoactive substances, such as party pills and other legal highs, as they are synthesised to be one step ahead of existing controls.
From next August, all psychoactive substances will be banned unless approved after costly and lengthy testing processes involving human clinical trials under a strict new regime.
The application fee will cost about $180,000 and testing up to $2 million.
The Ministry of Health regulators would look at toxicity, adverse effects and mental health effects before any new products were approved.
Under the new controls, legal high manufacturers will have to prove their products are safe.
Failure to do so could results in manufacturers being jailed for up to eight years.
* 34 per cent of frequent drug users noticed a new drug was available last year. a big increase from 9 per cent who noticed new drugs in 2008.
* 39 per cent mentioned 'Ecstasy-type' pills as the new drugs they had seen last year.
* 35 per cent of those who noticed new drug users said they had seen more young people taking drugs.
* 57 new psychoactive substances were identified by the European Monitoring Centre for Drugs and Drug Addiction this year, compared with only 13 in 2008.