It will come down to the observations of impairment coupled with the presence of drugs in your system. The pharmacist would be of little help. About all he could do is say that it might not impair some people ... which still doesn't m,ean it was reasonable to assume it would not impair you.
But the whole point is that the pharmacist can raise reasonable doubt, especially with the lack of a per-se limit. And if we can assume that some people can drive a car on the full dose, the pharmacist is effectively setting a floor to the per-se limit. If OP had 1/4 of that full dose in her blood, the lawyer can argue that the case is like claiming that someone with a BAC of .02 is guilty of DUI if it actually does go to court.
Sure, ANYTHING is possible, but I suspect a lot of jurors are going to be wondering why prosecution even brought this to trial.
In any event, listen to your attorney. If the officer is half way decent at his job and can articulate the objective signs of impairment, the state may well have a good case - even if the officer is an unlikeable lout.
Yes, but if the officer is an unlikeable lout and the OP had 1/4 the per-se amount in her system, OP's lawyer has to just go up there and laugh about .02 BACs for a little bit and remind the jury that drowsy driving could have been a much better explanation.
Prosecution has to prove beyond all reasonable doubt that either OP had so much medication in her system that a reasonable person would have been impaired or that OP would not have been impaired without the medication but was driving impaired with it. If the prosecutor can't prove it beyond all reasoanble doubt, OP should be found not guilty.
2nd listening to the attorney, though. He seems intent on bringing this to trial if prosecution pursues it.