Aside from questions about whether it's really safe to take drugs like that (which are excellent questions to ask), is it wise?
Even if the pills are harmless, would you really want to cut down sleep like that? I know I have wished for less sleep at times, but really what's so urgent that it can't wait until the morning? Do you think you might just end up packing more into your day and becoming more stressed, even if you didn't have a boss forcing you to do so?
I'm going to have to go with the "let the body work naturally" camp on this one.