Description
Mepyramine is a first generation antihistamine that acts as an inverse agonist at the histamine H
1 receptor. It is reported to bind with high affinity to a G
q/11 protein-coupled form of the receptor and to promote a G protein-coupled inactive state of the H
1 receptor that interferes with the G
q/11-mediated signaling of the endogenously expressed receptor, as well as to reduce G protein availability for other non-related receptors associated with this signaling pathway. Mepyramine has been shown to inhibit histamine-induced inositol phosphate production with a log EC
50 value of -7.94.
Chemical Properties
solid
Uses
Pyrilamine maleate Selective inverse agonist for the H-1 histamine receptor. Pyrilamine Maleate is commonly utilized as a radioligand ([3H]Mepyramine) binding assay for the H1 receptor. And also used to exhibit blocking ability of KCNQ/M channels which is potentially related to an adverse effect seen in excess intake of antihistamines.
Uses
A histamine H1 receptor antagonist
Uses
Mepyramine maleate is used as bulk pharmaceutical (antihistaminic). Product Data Sheet
brand name
Histavet-P [Veterinary] (Schering-Plough Animal Health); Pymafed (HoechstRoussel).
General Description
Pyrilamine, 2-[4-methoxybenzyl[2-dimethylamino)ethyl]-amino]pyridine, is available as theacid maleate salt (1:1), which is a white crystalline powderwith a faint odor and a bitter, saline taste. The salt is solublein water (1:0.4) and freely soluble in alcohol. A 10% solutionhas a pH of approximately 5. At a pH of 7.5 or above,the free base begins to precipitate.
Pyrilamine differs structurally from tripelennamine byhaving a methoxy group in the para position of the benzylradical. It differs from its more toxic and less potent precursorphenbenzamine (Antergan) by having a 2-pyridyl groupon the nitrogen atom in place of a phenyl group.
Clinically, pyrilamine and tripelennamine are consideredamong the less potent antihistaminics. They are highly potent,however, in antagonizing histamine-induced contractionsof guinea pig ileum. Because of the pronounced localanesthetic action, the drug should not be chewed, but takenwith food.
General Description
White crystals or powder. Melting point 100-101°C. Bitter saline taste. An antihistaminic medicine.
Air & Water Reactions
Water soluble.
Reactivity Profile
PYRILAMINE MALEATE is an acidic salt of an amine. Usually does not react as either oxidizing agents or reducing agents but such behavior is not impossible. May be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen may be generated in combination with strong reducing agents, such as hydrides.
Health Hazard
SYMPTOMS: Symptoms of exposure to PYRILAMINE MALEATE may include drowsiness, potentiation of the sedative effect of barbituates, fatigues, vertigo, incoordination, tremor, muscle weakness, dryness of the mouth and throat, tinnitus, pupillary dilation, blurred vision, urinary retention, impotence, epigastric and intestinal pain, anorexia, nausea, vomiting, diarrhea, excitation, euphoria, insomnia, nervousness, palpitation, tachycardia, hypotension, hypersensitivity reactions, respiratory depression, coma and delirium.
Fire Hazard
Flash point data for PYRILAMINE MALEATE are not available, however PYRILAMINE MALEATE is probably combustible.
Biological Activity
Selective inverse agonist for the H 1 receptor. Inhibits histamine induced inositol phosphate (InsP) production (log EC50 = -7.94) and intracellular calcium mobilization. Sequesters G q/11 protein, reducing its availability for other receptors associated with the same signaling pathway.
Biochem/physiol Actions
Pyrilamine maleate is a H1 histamine receptor antagonist. Pyrilamine maleate induces sleep in vertebrates. In Cassiopea, it induces concentration dependent dormancy.
Safety Profile
A human poison by
ingestion. An experimental poison by
ingestion, subcutaneous, intravenous, and
intraperitoneal routes. Experimental
reproductive effects. Questionable
carcinogen with experimental tumorigenic
data. Mutation data reported. An
antihistamine. When heated to
decomposition it emits toxic fumes of NOx.
Veterinary Drugs and Treatments
Antihistamines are used in veterinary medicine to reduce or help
prevent histamine mediated adverse effects; predominantly used in
horses.
