Mepyramine

Mepyramine, also known as pyrilamine, is a first generation antihistamine, targeting the H₁ receptor as an inverse agonist.^[1] Mepyramine rapidly permeates the brain, often causing drowsiness.^[2] It is often sold as a maleate salt, pyrilamine maleate.

Mepyramine

Clinical data
Other names	Pyrilamine; N-[2-(dimethylamino)ethyl]-N-[(4-methoxyphenyl)methyl]pyridin-2-amine
AHFS/Drugs.com	International Drug Names
MedlinePlus	a606008
Routes of administration	oral, topical,
ATC code	R06AC01 (WHO) D04AA02 (WHO)
Legal status
Legal status	In general: Over-the-counter (OTC)
Identifiers
IUPAC name N-(4-methoxybenzyl)-N',N'-dimethyl-N-pyridin-2-ylethane-1,2-diamine
CAS Number	91-84-9 Y 59-33-6 (maleate)
PubChem CID	4992
IUPHAR/BPS	1227
DrugBank	DB06691 N
ChemSpider	4818 Y
UNII	HPE317O9TL
KEGG	D08183 Y
ChEBI	CHEBI:6762 N
ChEMBL	ChEMBL511 Y
CompTox Dashboard (EPA)	DTXSID9023542
ECHA InfoCard	100.001.912
Chemical and physical data
Formula	C17H23N3O
Molar mass	285.391 g·mol−1
3D model (JSmol)	Interactive image
SMILES O(c1ccc(cc1)CN(c2ncccc2)CCN(C)C)C
InChI InChI=1S/C17H23N3O/c1-19(2)12-13-20(17-6-4-5-11-18-17)14-15-7-9-16(21-3)10-8-15/h4-11H,12-14H2,1-3H3 Y Key:YECBIJXISLIIDS-UHFFFAOYSA-N Y
NY (what is this?)  (verify)

The medication has negligible anticholinergic activity, with 130,000-fold selectivity for the histamine H₁ receptor over the muscarinic acetylcholine receptors (for comparison, diphenhydramine had 20-fold selectivity for the H₁ receptor).^[3]

It was patented in 1943 and came into medical use in 1949.^[4]It was marketed under the names Histadyl, Histalon, Neo-Antergan, Neo-Pyramine, and Nisaval.^[5] In the 1960s and 70s it was a very common component in over-the-counter sleep aids such as Alva-Tranquil, Dormin, Sedacaps, Sominex, Nytol, and many others.^[5] The US FDA included it in the list of chemicals and compounds barred from use in over-the-counter nighttime sleep aid products in 1989.^[6]

It is used in over-the-counter combination products to treat the common cold and menstrual symptoms such as Midol Complete.^[7] It is also the active ingredient of the topical antihistamine creams Anthisan^[8] and Neoantergan^[1] sold for the treatment of insect bites, stings, and nettle rash.