Mepyramine
Mepyramine, also known as pyrilamine, is a first generation antihistamine, targeting the H1 receptor as an inverse agonist. It rapidly permeates the brain often causing drowsiness. It also has anticholinergic properties. However, its anticholinergic potency is negligible compared to its antihistaminergic activity; it has an H1 to muscarinic Ki ratio of 130,000 to 1, compared to a ratio of 20 to 1 for diphenhydramine.
It was patented in 1943 and came into medical use in 1949. It is used in over-the-counter combination products to treat the common cold and menstrual symptoms. It is also the active ingredient of the topical antihistamine creams Anthisan and Neoantergan sold for the treatment of insect bites, stings, and nettle rash.
