Hawke's Bay psychiatric and addiction services are being urged to prepare for an influx of people dealing with intense synthetic cannabis withdrawals.

Experts have warned stockpiling, fire sales and an added burden on health services may occur when all synthetic cannabis products are withdrawn from sale within a fortnight.

In a Government policy reversal, Associate Health Minister Peter Dunne said on Sunday all legal high products would be banned until they could be proven "low-risk", with a law change to be introduced under urgency to Parliament next week.

Hastings Deputy Mayor Cynthia Bowers, a staunch leader against legal highs, was pleased about the ban but said "it has taken too long".


"Common sense has prevailed ... Clearly Labour were going to announce their policy on the issue and it put some pressure on the Government, but I think the pressure from local leaders and communities, the power of the people. That really was so strong the Government couldn't possibly ignore us."

She described the news of the blanket ban as a relief and said there was an "element of satisfaction", knowing the Bay had played a large part in the war against legal highs.

Hastings Mayor and Local Government New Zealand president Lawrence Yule said addicts could stockpile and withdrawal problems might become apparent as supplies ran out.

"If [an addict's] life has been ruined by psychoactive substances, then they could look at this as an opportunity to get themselves off it with the proper support, and that could be a life-changing experience," Mr Yule said.

District health boards and drug rehabilitation agencies had a responsibility to support addicts, he said.

Adult Selections Napier, the last remaining legal high retailer in Hawke's Bay, did not wish to comment yesterday, while Discretions store owner and former stockist Gordon Arcus could not be reached.

St John Hawke's Bay district operations manager Stephen Smith said an increase in emergency call-outs involving legal highs had been seen in the past 6-12 months. "We have been involved in serious incidents where the use of these substances has led to irrational behaviour, seizures and cardiac arrest.

"People under the influence of legal highs are frequently violent, anxious and experience rapid heartbeat and other concerning symptoms."

Drug Foundation chief Ross Bell said a ban would have negative consequences, warning of fire sales, stockpiling and over-consumption, while National Poisons Centre toxicologist Leo Schep said psychiatric and addiction services needed to prepare for an influx of people with legal high withdrawal symptoms.

Meanwhile, Prime Minister John Key admitted the Government had made a mistake leaving 41 synthetic products on the market, after passing the Psychoactive Substances Act last July.

He also admitted a black market was likely to develop.