Any advice before med switchback?

[Dignan]

I was wondering if anyone knew how to tell (or what tests to ask for) if a general feeling of cognitive slowness was related to long term Dilantin use or simply a side effect of my current drug Keppra. I am also having libido issues.

My doc hasn't been very helpful, and I think he is just giving me an educated guess (how educated it is I don't know). We are talking about moving me back to Dilantin since I felt fine when taking it (I got off of it due to some bone loss and the docs general sense that I shouldn't take it for so long), but before I go back to Dilantin I want to be certain that the issues I have experienced since I began tapering off of it were not related to the Dilantin to begin with. Obviously, if Dilantin were the problem, I wouldn't want to make things worse by going back to it.

I have a doc appt. in a few weeks, and I am sure he will tell me his opinion, but before I make the switch back, I WANT PROOF, that the Dilantin after effect is not the cause of the mental slowness and libido issues.

So, does anyone know of any testing (scans, particular bloodwork, or anything else) that I can have him either do or show to me help me feel comfortable before switching meds back??

Thanks.