What medicines are available to sleep for four hours, but feel like I got eight? I was listinging to Elliot in the Morning on DC101. They were talking about a drug that's being tested that allows a person to sleep two hours and feel fine. However, someone called in to say there's already something available that allows for four hours. What is it?

Summarized question: What drugs will make you feel fully rested on 4 hours of sleep?