Methapyrilene 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 in the UK.

[1] 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.

[2] All of these products were reformulated in the late 1970s[3] when methapyrilene was demonstrated to cause liver cancer in rats when given chronically.