A Rotorua addiction service manager is concerned locals have been illegally buying psychoactive substances spiked with methamphetamine since the sale of synthetic drugs was banned last May.
The Psychoactive Substances Act - passed in 2013 - regulated the availability of substances but allowed some products to stay on the market. In May 2014, the Psychoactive Substances Amendment Bill ended that interim product approval.
Te Utuhina Manaakitanga addiction service manager Donna Blair thought the number of people seeking help with psychoactive substances remained about the same.
However, the issues the service was dealing with have changed since it came into force.
"One of our concerns is that, now that it's no longer regulated, that we are seeing a small spike in the number of people coming through who are using psychoactive substances that have been spiked with methamphetamine."
Those drugs, which people were buying illegally, were even worse for them than the previously legal substances.
"That small number of people will report hand-on-heart that they don't use methamphetamine but when you blood test, it's in their blood stream."
Ms Blair declined to comment on whether the ban on psychoactive substances had been a good or a bad thing.
She said alcohol and cannabis remained the service's biggest issues, despite the continuing synthetic drug issues.
New Zealand Drug Foundation executive director Ross Bell said some people around the country had continued to use psychoactive substances after the ban. Synthetic cannabis was on the black market alongside new products.
"The added challenge is that people can also buy these substances online and have them posted from overseas," said Mr Bell. A thriving black market for the drugs had always existed.
"If people want to get their hands on substances, then they still can."
The psychoactive substances law as it first passed had been "brilliant" and should have gone a long way to giving the Government greater control over the drug market, he said. However, the amendment removing products with interim approval from sale meant the Government had handed control to the black market:
"Users of these products are at real risk now because the black market doesn't care for consumer protection. It doesn't care for potency or dosage or quality control."
Rotorua Area Commander Inspector Bruce Horne said police were continuing to investigate sales of synthetic cannabis. "Since the [ban] complaints about behaviour in the CBD had dropped significantly. We're not getting reports from people feeling unsafe.
"We would acknowledge there's still a supply of synthetics out there and synthetics being sold on the black market but just because that's happening doesn't mean the actions that have been taken have been a failure. It's reduced opportunities and the impact on the wider community."