Christchurch Hospital has issued a stark warning to synthetic cannabis users, advising people in Canterbury to be "extremely cautious".
The hospital's emergency department has seen a number of people suffering from "probable severe synthetic toxicity", with seven people treated within 24 hours, and three needing admission to the Intensive Care Unit.
Canterbury DHB has seen a "noticeable increase" in patient attendances at the emergency department for side effects of synthetic cannabis use, says Emergency Medicine Specialist Dr Paul Gee.
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Some of the effects are minor but others are more serious, he says. In August, a man suffered a cardiac arrest after using synthetic cannabis but was successfully resuscitated.
The substance AMB-FUBINACA has been identified among analysis of various patients' toxicology levels. The same substance, according to Christchurch Hospital, has been linked to numerous deaths during the past year in Northland.
Patients have been unable to disclose any useful information about the lethal drug, the hospital says, so it is unable to give any information to help drug users identify it.
"These are dangerous drugs available and taking them could seriously harm or kill you," Dr Gee says.
Police said in June they had sent more synthetic drugs than normal to the Institute of Environmental Science and Research (ESR) for testing - many of which tested positive for AMB-FUBINACA.
AMB-FUBINACA was developed by American pharmaceutical corporation Pfizer, which makes a number of drugs including diazepam, venlafaxine and Viagra.
The drug was patented in 2009, but development was abandoned and it was never tested on humans. But a few years later it appeared for sale online as a designer drug.
There are around 200 known synthetic cannabinoids, ranging in strength from weaker than natural cannabis to the likes of AMB-FUBINACA - dozens of times stronger.