Originally Posted by cess

http://en.wikipedia.org/wiki/Doxylamine

Doxylamine is a member of the ethanolamine class of antihistamines and has anti-allergy power superior to almost every other antihistamine on the market, with the exception of diphenhydramine (Benadryl).[1] It is also the most effective over-the-counter sedative available in the United States,[2] and is more sedating than some prescription hypnotics. In a study, it was found that doxylamine succinate is possibly more effective than the barbiturate phenobarbital for use as a sedative.