Yes you can in every pharmacy. Just ask and no problem. I only try Caverta once (red diamond) ... 700-800 baths for 4 pills and no bad post-effects except very red eyes (because mixed with a lot of beers). I think Viagra is a little bit more expensive (but not sure).
Good to try when you are drunk and tired as it gives you power for all the night, but if you have no true erection problem, one half is far enough. You can ask the phamacy holder to cut them for you.