Eight people have been treated at Christchurch Hospital after taking synthetic cannabis.

At least three people have been admitted to intensive care and others treated within 24 hours in Christchurch after using synthetic cannabis.

The Canterbury District Health Board (CDHB) issued a warning about the illegal drug after a rush of people suffering from potentially severe synthetic cannabis toxicity ended up in Christchurch Hospital.

Emergency medicine specialist Paul Gee said there had been a noticeable increase in people needing emergency help due to the side effects of synthetic cannabis use.

Eight people have been treated in Christchurch over the last 24 hours, with three having to be admitted to the intensive care unit.

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CDHB said all the patients were male between the ages of 20 and 56 years old.

Gee said a man suffered a cardiac arrest last month after using synthetic cannabis, but was successfully resuscitated.

Toxicology analysis has identified the substance taken by the latest patients as either AMB-FUBINACA or AB-FUBINACA.

AMB-FUBINACA has been linked to several deaths in the North Island during the past year.

In a statement, the CDHB said it could not give any information to help drug users identify the "lethal" drug as the patients were "unable to disclose any useful information".

The board urged synthetic cannabis users in Canterbury to be extremely cautious.

"There are dangerous synthetic drugs available and taking them could seriously harm or kill you," Gee said.

Anyone needing help with addiction can contact Tuhauora, Christchurch's Central Coordination Service, by emailing chchaod@odysseychch.org.nz or can call the Alcohol and Drug Helpline on 0800 787 797.

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