Cupid Shop owner Carl Lapham said some users would ''flip out'' in a couple of weeks' time when Parliament passes urgent legislation to ban synthetic drugs.
''There'll be that many going cold turkey. They'll all want the help at the same time, and the health department won't have the resources to cope with it.''
Not all users of synthetic highs were badly affected: some held down jobs, and had normal lives, he said.
For many, it was akin to having a glass of wine with a meal, he said.
''We all have our vices ... we all do something in our life that we wish we didn't.''
Some people should not drink alcohol or gamble, but those activities were not banned, he said.
He told the Otago Daily Times yesterday it was too early for users to stockpile.
''Pay days start [Tuesday], Wednesday, Thursday.
''Not the sort of question you'd ask today.
''Nobody's stocking up, because they haven't got any money in their pocket.''
He had sympathy with opponents, but ''I'm not the moral police''.
''At the end of the day, I can see for and against.''
Dunedin father Wayne McFadyen, whose 26-year-old son was using synthetic drugs again after going clean for about six months, blamed the Government for not acting sooner and more decisively.
''I hold the Government totally responsible. They're the ones allowing it.
''The Government don't care because we're the poor people ... they don't give a stuff about the community,'' he said.
He believed Parliament should be recalled from recess immediately to introduce an outright ban.
Mr McFadyen said his son relapsed about a month ago, and ''this time round he's worse''.
He was ''out of control'' and desperately needed help.
Dunedin toxicologist Dr Leo Schep, of the National Poisons Centre in Dunedin, said the centre was pleased with the impending ban, which would reduce harm caused by the substances.
Their legality gave users a false sense of security, Dr Schep said.
