Mepyramine, also known as pyrilamine, is a

first-generation antihistamine H1 antagonists, also called H1 blockers, are a class of medications that block the action of histamine at the H1 receptor, helping to relieve allergic reactions. Agents where the main therapeutic effect is mediated by negative modulation of his ...

, targeting the H₁ receptor as an

inverse agonist In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse agon ...

. Mepyramine rapidly permeates the brain, often causing

drowsiness Somnolence (alternatively sleepiness or drowsiness) is a state of strong desire for sleep, or sleeping for unusually long periods (compare hypersomnia). It has distinct meanings and causes. It can refer to the usual state preceding falling asleep ...

. It is often sold as a

maleate Maleic acid or ''cis''-butenedioic acid is an organic compound that is a dicarboxylic acid, a molecule with two carboxyl groups. Its chemical formula is HO2CCH=CHCO2H. Maleic acid is the ''cis'' isomer of butenedioic acid, whereas fumaric acid ...

salt, pyrilamine maleate. The medication has negligible

anticholinergic Anticholinergics (anticholinergic agents) are substances that block the action of the acetylcholine (ACh) neurotransmitter at synapses in the central nervous system, central and peripheral nervous system. These agents inhibit the parasympatheti ...

activity, with 130,000-fold

selectivity Selectivity may refer to: Psychology and behaviour * Choice, making a selection among options * Discrimination, the ability to recognize differences * Socioemotional selectivity theory, in social psychology Engineering * Selectivity (radio), a ...

for the

histamine Histamine is an organic nitrogenous compound involved in local immune responses communication, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Discovered in 19 ...

H₁ receptor over the

muscarinic acetylcholine receptor Muscarinic acetylcholine receptors (mAChRs) are acetylcholine receptors that form G protein-coupled receptor, G protein-coupled receptor complexes in the cell membranes of certain neurons and other Cell (biology), cells. They play several role ...

s (for comparison,

diphenhydramine Diphenhydramine, sold under the brand name Benadryl among others, is an antihistamine and sedative. Although generally considered sedating, diphenhydramine can cause paradoxical central nervous system stimulation in some individuals, particula ...

had 20-fold selectivity for the H₁ receptor). It was patented in 1943 and came into medical use in 1949. It was marketed under the names Histadyl, Histalon, Neo-Antergan, Neo-Pyramine, and Nisaval. In the 1960s and 70s it was a very common component in over-the-counter sleep aids such as Alva-Tranquil, Dormin, Sedacaps,

Sominex Sominex is the trademarked name for several over the counter sleep aids. Different formulations of Sominex are available, depending upon the market. Both the US and UK formulations contain a significant dose of a first generation antihistamine w ...

, Nytol, and many others. The US

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...

(FDA) included it in the list of chemicals and compounds barred from use in

over-the-counter Over-the-counter (OTC) drugs are medicines sold directly to a consumer without a requirement for a prescription from a healthcare professional, as opposed to prescription drugs, which may be supplied only to consumers possessing a valid pres ...

(OTC) nighttime sleep aid products in 1989. It is used in over-the-counter combination products to treat the common cold and menstrual symptoms such as Midol Complete. 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.

References

{{Navboxes , title =

Pharmacodynamics Pharmacodynamics (PD) is the study of the biochemistry, biochemical and physiology, physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or comb ...

, titlestyle = background:#ccccff , list1 = {{Histamine receptor modulators {{Monoamine reuptake inhibitors {{Sigma receptor modulators 2-Pyridyl compounds H1 receptor antagonists Muscarinic antagonists 4-Methoxyphenyl compounds Sigma receptor modulators Dimethylamino compounds

See also

References