HISTAMINE

HISTAMINE

Histamine is a potent vasodilator found in normal tissues and blood. It occurs widely in nature, e.g. in ergot and in all the organs and tissues of the human body as a result of putrefactive processes. It stimulates the secretion of pepsin and acid by the stomach. Histamine is converted into the corresponding aldehyde and ammonia by the flavoprotein, diamine oxidase. Some undegraded histamine is excreted in the urine in the form of the N-acetyl and N-methyl derivatives.

Histamine can be obtained by decarboxylation of the amino acid histidine which can be isolated from natural sources or can be prepared synthetically.

Histamine, m.p. 83-84°, is a crystalline compound which is freely soluble in water, alcohol and hot chloroform, and sparingly soluble in ether. It behaves as a di-acid base, forming salts such as the dihydrochloride.
Histamine dihydrochloride (Brand Names: Amin-Glaukosan; Imido; Imadyl; Ergamine; Peremine), m.p. 244-246°, occurs as odourless, hygroscopic, colourless crystalline powder. It is very soluble in water; soluble in aleohol; practically insoluble in chloroform and ether. It is stored in airtight containers and protected from light.

Histamine produces a strong vasodilatation of the capillaries. In large doses it may cause an increase in their permeability, so that fluid and plasma proteins may escape into the extracellular fluid and lead to oedema. In lungs, histamine acts on smooth muscle, producing bronchiolar constriction. It has the effect of stimulating the gastric glands to produce hydrochloric acid. The lacrimal and nasal secretory glands are also stimulated.

Uses : Histamine causes stimulation of smooth muscles and lowers blood pressure by dilating the arterioles and capillaries. It also stimulates various glands of internal secretion, especially the gastric glands.
The main use of histamine is to diagnose impairment of the acid-producing cells of the stomach and in hyposensitization.


Adverse Effect

The adverse effects of histamine therapy include headache, flushing of the skin, general vasodilation with a fall in pressure, tachycardia, bronchial constriction and dyspnoea, visual disturbance, vomiting, diarrhoea, and other gastro-intestinal effects



                                                                    

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