Experimental "next-generation" party pills designed to side-step next month's Government ban have hit the streets.
One test batch put a man who took them in hospital.
A Weekend Herald investigation has found at least one of the new pills contains a substance police believe is illegal.
A legal loophole means party pill makers can put products on the market without having to prove they are safe.
Doctors say the new pills being created in the rush to meet demand may be as dangerous as those being banned.
The Government aims to have its ban on core party pill ingredient BZP in effect by Christmas.
The law change will classify BZP as a class C drug.
A range of pills being marketed as "non-BZP" is now on shop shelves. The pills, with names such as "Neuro Blast", cost $40 for a pack of three.
A man who took part in a trial of non-BZP pills for Auckland company London Underground was hospitalised when he found himself almost unable to breath, went numb and had his blood pressure almost double after taking two pills in August.
He said he felt he was going to die when he was hit by a "a surge of adrenalin into my heart".
The Ministry of Health says other users of next-generation pills have had heart palpitations and their fingers or toes have turned blue.
The Neuro Blast pills are being investigated by the police national drug intelligence bureau after scientific testing found they contained a stimulating substance called diphenyl prolinol.
Bureau head Mick Alexander said police believed they could prove this was a close version or "analogue" of pipradrol, a stimulant with side effects ranging from insomnia to psychosis and convulsions.
He would not comment further, saying legal action was possible.
London Underground refused to discuss the pills with the Weekend Herald and did not return calls about the police allegations.
A staff member, who would only give his name as Stan, said he knew of problems experienced by one of the trial participants but would not say what was in the pills.
He said Neuro Blast was no longer in shops - but the Weekend Herald bought some in the city yesterday.
Mr Alexander said police were aware parts of the multi-million dollar party pill industry were "pushing boundaries" with "obscure compounds" before the BZP ban.
"There are party pill suppliers selling pills without even knowing what is in them. If I was a user I would just stay away."
Mr Alexander said the party pill industry was exploiting a loophole in the Misuse of Drugs Act which meant manufacturers did not have to prove pills were safe before putting them on sale, as happened with food and medicine. Instead, the onus was on police to prove the pills were dangerous
The loophole will be addressed in a proposed Law Commission review of the 30-year-old act.
The Ministry of Health's chief public health adviser, Dr Ashley Bloomfield, said BZP party pills were banned because of safety issues "and there is no reason to expect there won't be safety issues with any of these purported newer and safer substances".
"The onus should be on manufacturers to show the safety and they have shown no inclination to do the studies you would need to do to show safety."
Users should "quite simply not take these pills".
Associate Health Minister Jim Anderton, who promoted the BZP ban, agreed the act needed to be reviewed "tomorrow" to place the onus of proof on pill makers but said it was a major job and the Law Commission would not begin work on it until next year.
He said the attempts to get around the BZP ban showed the party pill industry's motivation was not to be careful about the safety of users.
"It is to slip through the cracks and make money."
National MP Jacqui Dean said Mr Anderton had been too slow getting the ban into law, giving party pill manufacturers a head start.
"With the minister signalling he's going to do something for about 18 months, the people who established those markets and are making big money out of party pills have been working on the next generation."
Matt Bowden, a party pill supplier and head of the industry's Social Tonics Association, said he believed party pills should have to go through the same testing process as medicines but the lack of regulation was the reason there were breaches.
"Unless we have the Government work with us, all we can do is put out voluntary regulations and people will try to get around them."
