Stores selling party pills and synthetic cannabis are heavily discounting stock before some chemicals become illegal on Friday.
The Government has banned the chemical DMAA, which is found in most party pills and three other chemicals found in fake cannabis.
Previously, BZP, a chemical found in legal highs, was made illegal.
John Frew, the co-owner of a store selling party pills, believes the latest move will end the sale of party pills altogether.
But Associate Health Minister Peter Dunne says the ban is a temporary measure, while legislation is developed to permanently regulate the industry.