Photo: RNZ / Alexander Robertson
Concerns have been raised that people using ADHD medication could be caught out by new police roadside drug testing.
Police are proposing to use a device that can test for cocaine, THC, methamphetamine and MDMA.
Legislation to allow roadside drug testing has passed its third and final reading in Parliament.
The legislation gives police powers to undertake random roadside saliva tests, similar to drink-driving enforcement.
Drivers who return a positive result will have their saliva sample sent for further laboratory testing. If that subsequent test finds qualifying drugs and an indication of recent use, the drivers would be issued a fine and demerit points.
Two positive roadside tests would be required before a driver is prohibited from driving for 12 hours.
Both meth and MDMA are amphetamines, but so is the ADHD medication dexamphetamine, and that could mean anyone using it could fail the tests as a result.
A pharmacist and senior lecturer in Biosciences at AUT is worried about the lack of information she has seen over what the new testing could be mean for people with prescriptions like dexamphetamine.
"I have seen nothing anywhere that has spoken about how this is going to be managed," Dr Catherine Crofts told Morning Report.
"We know that some of the tests that are out there in the community do cause some cross reactivity, and I've just found that there are some that don't.
"But we haven't seen anything about what the police are going to do or how it is going to be managed when somebody who is cross reacts, who is legally on these medicines."
Dr Crofts said about 50 percent of people with ADHD in New Zealand are taking dexamphetamine or lisdexamfetamine, which is becoming increasingly popular.
She said due to the shortage of methylphenidate - such as Ritalin or Concert - a lot of people are switching over.
"We're only talking about, a couple of percent of people in New Zealand likely to be affected," Dr Crofts said.
"But those people who are affected, it could have quite drastic impact to their employment if they're unable to drive, if they've got a sudden 12-hour stand down, how they manage childcare, (and) their daily living."
Dr Croft said she hoped there would be exceptions made for those on ADHD medication, with a photo of the prescription label or something similar to use as a medical defence at a potential roadside drug testing screening.
She also quashed concerns medications like dexamphetamine can negatively impact a user's ability behind the wheel.
"Only as much as that can improve somebody's ability to drive," she said.
"There's evidence out there that shows that people with ADHD who take these medicines have a lower risk of a road traffic accident than people who are unmedicated and on the road."
Dr Croft also said her understanding is that the majority of people using medical cannabis are only using the CBD component, and not THC.
"THC can increase your risk of impairment, but for most people on CBD, it shouldn't be detected in the drug testing regardless, "she said.
Meanwhile, the AA has welcomed the move and called it long overdue in its efforts to aid police.
It said in a statement that more than 100 road deaths a year have involved a driver subsequently found to have drugs in their system.
"Both illegal drugs and some prescription medications can affect people's focus, reaction times, and have other impacts that can make someone unsafe to be in control of a vehicle," AA road safety spokesperson Dylan Thomsen said.
"Roadside saliva tests have been used in Australia and Europe for years - it's about time New Zealand introduced them too.
"Close to half of road deaths in New Zealand involve people impaired by alcohol, drugs or both. The police have dramatically increased alcohol testing recently and the AA sees adding roadside drug testing as another way to turn the tide on impaired driving."
Thomsen said that many people believe their chances of being caught driving drugged are slim, and that new testing can help change that perspective.
"Some people have expressed concerns about being unjustifiably inconvenienced by the length of time drug tests take compared to alcohol, or highlighted concerns about their accuracy," he said.
"Because of the high number of deaths and injuries involving impaired drivers on our roads, the AA believes the benefits of having these tests outweigh arguments against them."
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