Pot and alcohol are taken to induce a dysfunction alone.
True, but the crime you're referencing here isn't the taking of drugs, but the driving of the car while impaired. So while a person may take an anithistamine for a legitimate purpose, they make a choice to drive while their faculties are possibly impaired.
That seems just as premeditated to me.
The antihistamine use is extended to drunkards, too, and would protect them if only they weren’t drunk.
I’m not arguing that those who drive drunk can’t be given the same allowance we give others for talking on a cell phone, while taking antihistamines, etc. My problem is with their compounding the problem with something meant only to pervert their rational abilities alone.