Wow, this thread really has a lot of bad good advice. In general, yeah, it's good advice not to shoot ANYTHING, but you've got to keep in mind that some of us just like injecting things, and so telling them not to without providing any useful information is only going to worsen their chances of A.) making an educated and informed decision on the matter and B.) surviving it if they decide to go ahead with it.
I'm actually researching the same question on isopropyl alcohol right now, but for the sake of injecting Mylan fentanyl patches, and it seems doable, though I don't know all the precise details and I'd suggest that no one try this unless THEY happen to know them. However, I've found quite a few sources stating that rubbing alcohol, even as low as 70% from the drugstore, will completely evaporate and should therefor be safe, though you must make sure it is fully evaporated and allow it to dry at temperatures of 35c or above. How to filter benzo's, I really don't know, and again, this is just the word on the street so I'd say hold off on trying anything until you can find solid evidence on all the details of it. As for me, I sure aint prepared to try it yet!