A drug that replaced BZP in party pills has been linked to cerebral haemorrhages and strokes in users.
It took four years for DMAA to be banned under the new temporary rules set up to stop new legal highs from springing up.
Associate Health Minister Peter Dunne banned the drug in February after getting advice that it was literally blowing the minds of users.
Dimethylamylamine (DMAA) had been patented in 1944 as a Nasal decongestant. Health officials told Mr Dunne the drug had replaced BZP after the latter was banned in 2008.
But by 2012, the amount in doses had soared and the drug had morphed from the party pill market into dietary supplements and sports nutrition products.
It was a similar pattern to that followed by BZP, which health monitoring later tracked as being used by 15 per cent of the population.
Mr Dunne was told DMAA doses had increased as the drug became entrenched as a BZP replacement. The doses went from 50mg in pills up to 5gm packets of powder.
In the 18 months leading up to the ban, emergency medicine specialists reported at least five cases of cerebral haemorrhage.
They included a 23-year-old woman who took the recommended two-tablet dose of Pure X-S. Inside 30 minutes, she started vomiting and twitching and a brain scan showed bleeding across the frontal lobe.
Others included a man aged 36 who took Cocaine Party Powder before suffering a headache and weakness on his right side. He woke with weakness on his left side and a facial droop.
Other reported problems included a stroke and a young woman who reported "excessive bleeding" and bruises while taking a dietary supplement containing DMAA.
NZ Drug Foundation director Ross Bell said BZP had become a product which was "self-prohibiting". Those who used it did so sparingly because it came with a crushing hangover.
"But the new ones are said to be very moreish. People kept taking them," said Mr Bell.
An early version of synthetic cannabis had appeared on the market about seven years ago with few problems reported, he said. It had been banned - and was replaced with Kronic and similar substances that were reported to have a greater number of problems.
Papers released under the Official Information Act showed concerns were raised about the temporary banning system used to get rid of synthetic cannabis products.
Treasury officials warned health bureaucrats that users might find other substances that were "potentially more dangerous alternatives". The Treasury called for greater research before the temporary scheme was put in place.
Treasury officials also warned Mr Dunne the plan to ban the drugs could be out of proportion to the "size and nature of the health risk".
Officials said the plan to issue temporary banning notices was too rushed.
Mr Dunne received advice from the National Poisons Centre showing the number of calls in the lead up to synthetic cannabis being banned. Staff at the centre got one call every two days at the peak of concerns. After the ban, the calls dropped to a maximum of four a month.By David Fisher @@DFisherJourno Email David