That's a good idea. Several years ago, up in Rhinelander, I skidded out on the access road to the trailer park I lived in, and hit a tree. (Black ice).
The cop who responded to the accident REALLY wanted to bust me for OWI. He put me through the field sobriety test, which I have trouble with due to physical disabilities. Luckily I passed that.
Bright sunny day...then he noticed that my eyes were slightly dilated due to a medication I take for tremors, and he was off to the races, and I was off for a blood test.
They tested for every drug of abuse known to modern man, including benzos, which I showed as having trace amounts of in my system, but did not test for Cogentin, which was the medication causing the dilated pupils. Luckily, after a long convo between a doctor and the cop, it was decided that amount of benzos in my blood stream was not enough to impair my driving. Left the hospital in the cop car and drove to my place (my truck still blocking traffic on the access road this whole time.) where I provided proof that the 2 benzos found in my blood stream were prescribed to me.
I narrowly escaped an OWI on that one. Interestingly, I got pulled over up here while still staying with (RIP) BFFs and apartment hunting for speeding (3mph over, yet! Got a warning) and the officer asked if I had any drugs on me or in the vehicle. I told him, "Only what's prescribed to me." He asked to see, so I dug the bottles out of my purse, he looked at the labels, and told me NEVER to carry any of those medications if they were not in the original RX bottles, since even if the drugs are prescribed to you, if you are carrying them loose, you can still be arrested for possession, or intent to distribute, depending on how many pills you have.