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"Thionylan" redirects here. The thionyl halides should not be confused with "thionylan" and include thionyl fluoride, thionyl chloride, and thionyl bromide.
Systematic (IUPAC) name
Clinical data
91-80-5 YesY
PubChem CID 4098
DrugBank DB04819 YesY
ChemSpider 3956 YesY
UNII A01LX40298 YesY
KEGG C11114 YesY
Chemical data
Formula C14H19N3S
261.387 g/mol
 YesY (what is this?)  (verify)

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.[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. It also provided the sedative component of Excedrin PM. All of these products were reformulated in the late 1970s when methapyrilene was demonstrated to cause liver cancer in rats when given chronically.[2]


Methapyrilene synthesis[3]

See also[edit]


  1. ^ The Birmingham Post Archive.
  2. ^ Lijinsky, W; Reuber, M.; Blackwell, B. (1980). "Liver tumors induced in rats by oral administration of the antihistaminic methapyrilene hydrochloride". Science 209 (4458): 817–819. doi:10.1126/science.7403848. PMID 7403848. 
  3. ^ Leonard, Frederick; Solmssen, Ulrich V. (1948). "2-Thenyl Substituted Diamines with Antihistaminic Activity". Journal of the American Chemical Society 70 (6): 2064–2067. doi:10.1021/ja01186a023.