Associate Minister of Health Peter Dunne will roll over the 16 notices that were due to expire this week.
He said there were another 12 notices due to expire in the coming weeks bringing the number of notices to be extended to 28.
Mr Dunne said he was extending the notices to ensure no banned substance and the 50 products containing them, slip back into the market before permanent psychoactive legislation, announced last month is in place.
"This is about making sure there is no gap for those who may look to bring substances back on the market before the new law forces them to prove their products are safe," he said.
Mr Dunne said there had been a 75 percent fall in the number of emergency call incidents around synthetic cannabis products since the drug notices were introduced, according to National Poisons Centre data.
"That is a huge fall and it began the very month the notices came into effect, and is a very good indication that what we are doing is working and keeping young New Zealanders safe,"said Mr Dunne.
He announced key details of the new psychoactive substances drug legislation last month. It will require distributors and producers of party pills and other legal highs to prove the products are safe before they can be sold.
The legislation will be introduced to Parliament later this year and will be in force by around the middle of next year.
The regime will establish a new regulator within the Ministry of Health which will be responsible for issuing approvals.
Companies wishing to sell such products will need to apply to this regulator with scientific data similar to that which is required for the assessment of new medicines.
Even once approved, any such products are likely to be subject to retail restrictions on purchase age and premises where they can be sold, which will further reduce their potential to cause harm.
- By Kate Shuttleworth of APNZ
