A spike in hospital admissions related to synthetic drug use in Christchurch has alarmed emergency services, amid suspicion that two deaths in the past fortnight were linked to use of the drugs.

St John territory manager Craig Downing fronted media today urging people to stay away from the "poison" and to remember "this is not cannabis in any way shape or form".

"They [synthetic drugs] are extremely dangerous. We don't know what's in them."

Downing said every day staff across the country, from Kaitaia to Bluff, went out to help others and did not expect to be abused by the synthetic drug users who were often violent.

"Our strong message is keep your hands off our ambos; they are not to be touched," Downing said.

On Saturday, a staff member was violently assaulted, he said.

Nineteen people in Christchurch have been affected by synthetic cannabis toxicity in the past fortnight, according to the Canterbury District Health Board. Two patients remain in intensive care.

Detective Inspector Greg Murton said police were very concerned about hospital admissions as a result of synthetic drug use, drugs he condemned as "extremely addictive and harmful".

Murton said they posed inherent risks as there was no way for people to know what they were taking.

"Dealers and manufacturers have no scruples about what these synthetic drugs are made up from and are only motivated by money."

Synthetic drugs, party pills and the like were a mix of unknown quantities of unknown chemicals in varying doses, some of which were "extremely toxic" and had been attributed to a number of deaths already, Murton said.

"Users are taking chances with their very life when they take party pills or so-called synthetic cannabis.

"When we have sometimes up to a dozen hospitalisations at once, as well as a number of fatalities attributed to synthetic drugs; that should be a wake-up call to anyone contemplating using them to stop immediately." 

Murton said police were focused on law enforcement and apprehension in regards to the suppliers and manufacturers of illegal drugs.

"Anyone with information relating to illegal drug activity, no matter how minor, is urged to contact police.

"You can do this by contacting your nearest police station or anonymously through Crimestoppers on 0800 555 111."

During the first week of September, St John reported attending 23 synthetic-drug-related callouts across the country. At one, the person was deceased.

Police Minister Stuart Nash said the issue was a matter of life and death and being taken seriously.

Nash said several government agencies were working on initiatives and changes were on the way.

"One of them, for example, is taking some of these worst substances out of Psychoactive Substances [Act] and putting them under the Misuse of Drugs [Act].

"It means the police have greater power to go after the people peddling this misery into our communities."