Toxicology analysis identified the substance taken by the recent patients as either AMB-Fubinaca or AB-Fubinaca. AMB-Fubinaca has been linked to numerous deaths in the North Island during the past year.
The Canterbury District Health Board said it was unable to give drug users tips to help identify this lethal drug because the recent patients "were unable to disclose any useful information".
Synthetic cannabis users in Canterbury should be extremely cautious.
The health board said drug and addiction services could be accessed at Tuhauora, Christchurch's Central Coordination Service using this email address: chchaod@odysseychch.org.nz.
The Alcohol and Drug Helpline was also available on 0800 787 797.