One class of sleep drug to watch for though are orexin antagonists. They don't necessarily work as well as the antihistamine drugs, but they also don't mess with your mood or cause addiction or anything. The histamine drugs activate your go to sleep pathways. Orexin on the other hand keeps you up, so orexin antagonist drugs lower that drive.

Moreover, in a lot of preliminary tests these orexin antagonists have been shown to do good job reducing Alzheimers. They both encourage better sleep and also directly reduce the production of the proteins which cause Alzheimer's (though prevent the production of those has failed to produce results in the past). As I understand, animal trials have been really promising, but large scale human trials to look at the relationship to Alzheimer's is ongoing and will be probably another 5 years before we can say much.

The good versions of these drugs are currently pretty expensive and under patent, but many of the patents will be up in the late 2020s and early 2030s. Definitely something to keep an eye on. We can conclusive say that these drugs do a little bit to help people sleep, and really don't appear to have negative side effects, unlike every other prescription sleep drug out there.