No. That essentially amounts to torture, which I'm against. That said, there are some pretty potent arguments in favour of this, so I can certainly respect your opinion.
For instance:
What makes it right to experiment on innocent animals, but not upon murderous humans?
How do we justify animal experimentation? By saying that it benefits humanity. We often talk about ex-prisoners as having paid their debts to society - could this not be another method by which that might happen?
Shit like that. Personally, the main reason I'm against it is that experimenting on other species, while not necessarily right, isn't as creepp, and doesn't set the same precedents that experimenting on our own species does. Although I could imaging being pretty pissed off were I a rabbit.
Just one thing to note, as the poster above me stated, that medical experiments don't necessarily imply anything painful or dangerous.
Oh, and while I'm typing, another thing.
Whether or not you think that this is right comes down in part to what you believe prison should be: A place for rehabilitation, or one of punishment. Personally, I think that rehabilitation is the more important aspect, and, as such, medical experiments become unjustifiable. That said, it leaves the tricky issue of what to do with people who have non-negotiable life sentences or, over in the States, the death penalty. If we decide that they are beyond rehabilitation, then where does that leave us in the whole debate?