Two more people have died from suspected synthetic drug overdoses in Christchurch in the last fortnight as the city grapples with a dangerous batch of the drugs.
Those on the front line say patients on synthetic cannabis are becoming more aggressive and turning on the people trying to help them.
St John's Craig Downing told 1 NEWS about one of these violent incidents.
"Last Saturday night we were called to a case that the ambulance staff responded to.
"They attended to a person and whilst in the back of the ambulance that person, without provocation or warning, violently attacked one of my staff," Mr Downing said.
"I'm extremely worried because we don't know from one patient to the next what's in this substance and as such every person is quite unpredictable."
Others dealing with Christchurch's less fortunate have also reported the new strain of synthetic cannabis causing issues.
"The latest batches are significantly more powerful than they've ever been, in fact up to 400 times the strength of THC which is really significant.
"From an addictive perspective one hit can get someone hooked on it," Christchurch City Mission's Matthew Mark says.
A paper is set to go to cabinet in the next few weeks with a plan on how to tackle the issue, including a possible law change.