Middlemore hospital in Auckland is seeing a sudden influx of drug users acting so violently they need sedation after taking what they thought were ecstasy pills.
Emergency care clinical head Vanessa Thornton says about 10 cases of people acting extremely aggressively have been seen over the past two weekends.
Ms Thornton says the people thought they had taken ecstasy.
But she says the symptoms are more similar to those people show after taking stimulant drugs, like methamphetamine.
Ms Thornton says the hospital has had to use six to eight security staff to control the individuals in order to sedate them.
She says the cases show how dangerous it is to buy drugs from the street, because there is no way of knowing what ingredients are really in the drugs.