Kronic is marketed as "legal weed", and its creators say there have never been reports of negative side-effects in the seven years it has been on the market.
However, the Australian Medical Association said using Kronic could cause severe paranoia, anxiety and panic attacks, high heart rates, agitation and restlessness.
Some people have ended up in hospital after smoking synthetic cannabis. Auckland City Hospital's emergency department often has one or two such patients a day.
The Government has promised to move on the drugs, which have names such as Kronic, Aroma and Dream - but not until next April.
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