<unk>  is an antihistamine and anticholinergic of the pyridine chemical class which was developed in the early 1950s. It was sold under the trade names Co-Pyronil and Histadyl EC. It has relatively strong sedative effects, to the extent that its primary use was as a medication for insomnia rather than for its antihistamine action. Together with scopolamine, it was the main ingredient in Sominex, Nytol, and Sleep-Eze. It also provided the sedative component of Excedrin PM. All of these products were reformulated in the late 1970s when<unk>  was demonstrated to cause liver cancer in rats when given chronically.
Methapyrilene
Cloricromen
Dihydroergocryptine
Plerixafor
Oxyphenisatine
Hymecromone
Cromolyn 
Niceritrol