We recently gave a educational presentation to a group of other lawyers about a somewhat less known crime of "driving-while-drugged." In Ohio, in addition to driving under the influence of alcohol, one can also be arrested and prosecuted for: (i) driving with a prohibited concentration of specifically enumerated drugs (usually illegal drugs) in one's system (called a "per se" violation); and/or (ii) driving under the influence of any drug (legal or illegal) that affects one's coordination to any "appreciable degree."
Obviously, this type of prosecution requires that the police legally obtain a blood sample (vs. the BAC alcohol collection machine) - so there are more medical/scientific issues with this type of prosecution than alcohol-related DUIs. Further, when it comes to the specifically enumerated drugs that cannot be in your system (there is a list in the DUI statute), you can still be guilty of the driving-while-drugged DUI even if you are in reality coordinated enough to drive. Further, and perhaps more importantly, this driving-while-drugged type of DUI can happen to almost anyone who is not careful with their prescribed or over-the-counter medications.
We have seen more of these types of cases with our elderly clients (who would never dream of driving after even one drink) who are on a series of prescribed medicines and with clients who suffered some old trama injury who unwittingly became addicted to the pain medication.
So, as the doctor and the pharmacists say, read the labels of all drugs you are taking to see about any warnings about operating "heavy machinery" (like a car) when taking the medication. And remember that you can be found guilty of a driving-while-drugged "per se" charge even if you are in fact completely sober at the time you are caught driving.