I've been on lunesta for quite some time .......of and on. For me .....I would never take it during the day.
It is a non-narcotic sleeping pill and I'm certain you cannot get high on it. I did build a tolerance to it though.......it just doesn't work for me anymore.
It's not a controlled substance -- I've never heard it being a problem to prescribe it to an addict. Hopefully it just helps him get some good sleep.