Doxylamine
"I have suffered from insomnia for decades and have tried many types of drugs for this issue.  I'm currently tapering off clonazepam and have found the Unisom tablets very helpful.  If I take half a pill I fall asleep within an hour and usually am able to go back to sleep in the night.  Took a whole pill last night and slept soundly.  I feel a bit tired today and will try to make do with half a pill from now on.  Nothing worse than insomnia!!"