The Government is bringing forward the start date for legislation on drugged-driving and is including some sedatives and anti-anxiety medication.
Transport Minister Steven Joyce said he was bringing forward by a month the start date for changes to legislation tackling drugged driving to November 1.
The Land Transport Amendment Act 2009 passed in June created a new offence for drivers impaired by drugs, introduced compulsory testing for suspected drugged-drivers and allowed blood testing for drugs.
Banned substances while driving would now include benzodiazepines - sedatives and anti-anxiety medications which can impair driving ability.
"When the legislation was passed in June drugged driving campaigners raised concerns around the exclusion of benzodiazepines," Mr Joyce said.
"I asked officials to look into it and they reported that this class of drugs should not be excluded from the legislation.
"With the support of most parties in Parliament the change to include benzodiazepines will be made this month as an addition to the Illegal Street Racing legislation."
Mr Joyce said police had indicated they were ready to implement changes and there was no reason to delay.
The new start date coincides with a ban on using hand-held mobile phones while driving.
"The drugged driving legislation is only aimed at drivers who pose a road safety risk. A driver who is not impaired will not be affected by this law," Mr Joyce said.