(Sorry this is so long, but I hope you find it useful. I've bolded some parts, not so much to emphasize them, as to show the main points in case it is too much reading for anyone.)

Christina sums it right up. I just looked up a bunch of information, both for my state and yours. The laws concerning this are about "intoxicants", regardless of source. I was not able to turn up anything specific, such as a list of exactly what prescription meds are considered intoxicant in your state. Or in mine.

In what I read, it is all about impairment. With something like alcohol, they've got that well-covered in specificity and easy tests to measure how much and how much trouble any given level means. It doesn't seem quite so clear in regards to other things. However, the bottom line seems to be that if they determine you're impaired, you'll be charged. So, it's not the taking, or the taking and not being impaired. It comes down to taking (of whatever) and being perceived to be impaired.

I'd be kind of surprised if they had a specific list. (Though there might be some kind of list with a "including but not limited to" clause, I could not find such a thing.) Though that's a bit scary in worst-case-scenario thinking (Omg, I've had too many Twinkies, and the sugar's making me drive crazy! Lol. ), it's probably mostly fairly obvious.

I'm perplexed a bit by their saying they're doing studies to determine when one is not considered under the influence. Any substance will be different for different people. Weight, metabolism etc all affect such things. So it can't (or shouldn't be) a time thing. The only thing I can think is if they figured some blood level they considered problematic (like what they do with BACs).

It may be obvious to you if you are impaired. Even if you don't think you are, it might not hurt to ask someone else what they think. It's not a guarantee of course, but it could help. (I had that happen once with prescription meds (not psych meds). Thought I was fine, so didn't ask anyone, right? When I got to my psych appt., she asked if I had driven. I thought it was an odd question. But she'd asked because she thought (and determined that) I was loopy. It was the last appt. of the day. She said she wouldn't have me driving and promptly drove me home(!) Kind of embarrassing!)

It's not about Seroquel. Also they're not saying it's narcotic or narcotic-like -- though I don't think you drew that conclusion. So it's weird they would say such a thing specifically, as the law does not seem to do so.