Health experts are warning of the dangers of so-called legal highs after six people were treated in one Cumbrian hospital in a week.
They were taken to West Cumberland Hospital, in Whitehaven, having been suspected to have taken Ivory Wave, which is advertised as bath salts.
They were suffering from extreme agitation and visual and auditory hallucinations.
The most serious cases were placed under cardiac monitoring.
North Cumbria University Hospitals Trust said in one case it took four members of staff to restrain a woman suspected of having taken the drug.
Consultant cardiologist Dr Kate Willmer said the symptoms were worse than with mephedrone, which was banned in April.
She said: "People are coming into the hospital in an extremely agitated state, with acute paranoid psychosis.
"If you try to give them anything to help them they are convinced you are trying to harm them so we have had to completely knock out two or three of them in order to treat them."
She said all of them had had very fast heart rates.
The long-term effects of the substance were not yet known, she said.
NHS Cumbria director of public health Professor John Ashton said: "There is no regulation for either illegal drugs or legal highs so people do not know what they are taking, what chemicals they contain or what the effects could be."