Senior Sergeant Craig Dinnissen, of Dunedin, said police were called to help St John at a party in Castle St about 11pm on Monday.
A 19-year-old student had taken MDMA and was "trying to scratch his eyeballs out", he said.
The drugs were tested and contained a little MDMA but a "huge quantity of bath salts".
The man was taken to Dunedin Hospital.
Snr Sgt Dinnissen said people needed to practise caution when it came to untested drugs, and preferably not take drugs at all.
"That's a huge risk ... you're taking your life into your hands by popping pills that aren't prescription."
About the same time, police were called to assist St John with crowd control after two "very drunk" students fell from a roof in the Queen St area.
Both had minor injuries.
KnowYourStuff, which tests the make-up of drugs, is operating in Dunedin for Re-Orientation.
New Zealand's illicit drug market has had a major shake-up due to Covid-19, a new report forecasting likely price increases and a drop in purity.
A post-Covid-19 drug landscape document created by Drug Information and Alert NZ found it was "almost certain" the changes in the country's illicit drug market would have wide-ranging social impacts.
The document shows there was a significant reduction in seizures of MDMA in mail and non-mail imports, which during the January to March period were down 7% on 2019.
"It is likely there will be a continued reduction in supply of MDMA to New Zealand. However, it is unlikely the effects of this reduced supply will be as significant as that of methamphetamine," the report read.
— Additional reporting The New Zealand Herald
