Donormyl (Doxylamine succinate) is over-the-counter antihistamine sleeping aid. The sleep-inducing properties of Doxylamine are comparable to that of secobarbital. It is known since 1948.
Donormyl works by inhibiting histamine receptors, thus it is also can be used to alleviate allergy and cold symptoms. Unlike common sleeping pills such as benzodiazepines and benzodiazepine-like drugs, doxylamine is not habit-forming and does not negatively affect sleep quality.