"Recreational doses are measured in tiny microgram quantities (less than the size of a match-head) so it is very easy to use more than intended," Dr Gee said.
Detective Senior Sergeant Jason Stewart said the last time a cluster of people had required treatment after using synthetic drugs in Christchurch was around six months ago.
"The real concern is that while five people have been treated in A&E in the last week, one person has been in ICU since their admission on Wednesday."
Police are working closely with customs and other agencies nationwide to target users and distributors of these substances as the effects of these drugs can be unpredictable and highly dangerous.
"In the case of synthetics users have very little knowledge of what they are actually taking and the public to be aware that there is a very real risk of serious harm or fatalities when people abuse any form of drug," Mr Stewart said.
Canterbury Police and Canterbury DHB advise drug users and the public to avoid any drug that is sold as an NBOMe or LSD-type drug and seek medical help for anyone suffering from adverse reactions.
If you see anything suspicious in your community contact Police straight away or call 111. Information can also be provided anonymously by calling Crimestoppers on 0800
555 111.
If you, your friend or family member wants assistance with drug addiction contact the Canterbury Police Organised Crime Unit or the Drug and Alcohol Help Line by calling 0800 787 797, emailing ada@adanz.org.nz or visit their website www.adictionshelp.org.nz