It would work but not in the way you think. The harder it is for him to understand what's going on that harder it is to channel his thoughts properly. Which in turn makes his powers harder to control. Of course if given some time, and depending on just how much of the drug is running around in his noggin, he'd probably be able to conjure up something. Most of the time he's probably going to conjure something underneath a cement block causing it to shoot up, or pull a hammer out of his pants or hat. He doesn't particular find explosives pleasing so usually he only messes with the battleground itself, or the weapons that are in play. Maybe conjure a cartoonish bugs to break a chain that's holding up a chandler. 

But the short of it is yes it would hurt his ability to properly use his powers.

As for his mouth while he has escape artistry in there he usually can't conjure something out of his own body usually other objects.