With respect to methyphenidate, the active chemical, yes, it can be plugged. You'd have to break down that coating though to get it in a nice available form obviously.
Oh, and for what it's worth? 60mg of methyphenidate in the form of crushed Ciba Ritalin tabs plugged, worked very nicely, giving a wonderful high and somewhat-cocaine like feeling, for about half an hour - before crashing and leaving the person in question sad, tearful, and feeling like a zombie, for approx. 6 hours, after which everything was more or less better.
The 30 minute rush you get from taking a good rush of nasal or rectal methylphenidate can NOT justify the horrible feelings you get afterwards for about 6 hours. It's a BAD BAD feeling, in my mind, worse than the comedown from amphetamines.
I still have many many ritalins and they are just sitting around for this very reason. I won't do it again. I just felt too horrible when I started to crash.
The peak was quite awesome though - everything you'd imagine a good speed or coke high to be. The crash was horrific, and absolutely negates any desire to do it again.
Play carefully