Hydroxyzine
"I was given this (50mg) as needed for anxiety/panic. The first time I took it, it knocked me out for 13 hours. When I woke up I was very groggy for at least 2 hours. After the mental  and physical exhaustion went away I did feel very calm and collected for quite some time. I am not taking it anymore because it is far too strong for me even in half or quartered doses. I'm happy if it works for you, but for me this was not good."