My dad takes ambien as well, it can really mess you up.
One time it was late and I guess he had taken some but not gone to sleep. He asked me to go to the store with him so I did and he drove. Went about 20 the whole way, lol, not too big a deal tho cuz we were on neighborhood roads with 35mph speed limit.
What killed me tho is he turned by stereo up nearly 100% full volume! My pioneer goes up to volume 40, and I tell him all the time never turn it up past 30, yet he was blasting it at 38 and 39 and then I would turn it down and tell him to stop, 10 seconds later full volume again. With Boston Z6's getting 250w a piece and 2 15" SI Magnums ported getting 800 a piece, I think it's a little unnecessary to turn it up that loud, lol.
The next day when I told him about it he didnt remember anything. Not one thing. Not driving, not going to the store, not turning the music up, nothing. Pretty scary if you ask me.