Notwithstanding the above, section 5A(3) of the act provides a defence for the person charged with the section 5A(1) offence if they can show that the specified controlled drug had been prescribed or supplied to them for medical or dental purposes. And that the drug was taken in accordance with directions given by the prescriber or the supplier, and in accordance with any accompanying instructions given by the manufacturer or distributor of the drug, and that the drug was obtained lawfully.

The individual may need to provide written evidence, such as a prescription receipt or the information leaflet that accompanied the medication. However, this defence would not apply if their driving were found to be impaired by any substances, as this is already covered in existing laws and remains an offence.