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Antihistaminic Agents Quick Revision

Antihistaminic Agents SUMMARY

1) Histamine, a biologically active substance potentiates the inflammatory and
immune responses of the body.
2) Anti-histaminic agents (or histamine antagonists ) are the drugs that
antagonise the action of histamine.
3) The first generation H1-antihistamines have a central effect so are used as
4) The second generation H1-antihistamines have low central effects so are used as anti-allergenic drugs.
5) Histamines are nitrogen containing organic compounds belonging to the
group of amines.
6) Histamines are synthesised and released by basophils and mast cells on
7) Diphenhydramine is a first generation antihistamine which is mainly used for treating seasonal allergies.
8) Dimenhydrinate is a comb ination drug as it comprises of diphenhydramine (53-55.5%) and 8-chlorotheophylline (not less than 44 – 47%) in a salt form, calculated on the dried basis.
9) Clemastine fumarate is the fumaric acid salt of clemastine. It is an antihistamine having antimuscarinic and moderate sedative properties.
10) Diphenylpyraline is an antihistamine used for treating allergy by competing with histamine to bind to the H1-receptor sites found on the effector cells.
11) Tripelennamine is an ethylenediamine derivative having anti -histaminergic property.
12) Chlorcyclizine is a first generation antihistamine belonging to phenylpiperazine class.
13) Meclizine hydrochloride is the hydrochloride salt form of meclizine, which is a synthetic piperazine having anti -emetic, sedative and H 1-antagonistic properties.
14) Buclizine hydrochloride is the hydrochloride salt form of buclizine, which is a piperazine H 1-receptor antagonist having antiemetic and anti -vertigo properties.
15) Chlorpheniramine maleate is a H1-recpetor antagonist.
16) Triprolidine hydrochloride is obtained by the reaction between equimolar amounts of triprolidine and hydrogen chloride.
17) Phenindamine tartrate is a phenylalkylamine sympathomimetic amine.
18) Promethazine hydrochloride is the hydrochloride salt form of promethazine, which is a phenothiazine derivative having antihistaminic, sedative and antiemetic properties.

19) Trimeprazine tartrate (or alimemazine) is a tartrate salt and a
phenothiazine derivative, which is used as an antipruritic agent.
20) Cyproheptadine is a first generation antihistamine wh ich is used as an
appetite stimulant and for treating allergic rhinitis and urticaria.
21) Azatadine maleate is a first-generation antihistamine. It is the dimaleate salt
of azatadine.
22) Astemizole is a long-acting, non-sedating second generation antihistamine.
23) Loratadine is an azatadine derivative and a second generation H 1-receptor antagonist.
24) Cetirizine (or zyrtec) is an orally active second generation H1-antagonist.
25) Levocetirizine is a third generation non-sedative antihistamine.
26) Cromolyn sodium is the sodium salt form of cromolyn, which is a mast cell
stabiliser having anti-inflammatory activity.
27) Cimetidine is a histamine congener and competitively inhibits the binding of
histamine to histamine H2-receptors.
28) Famotidine is a competitive H 2-receptor antagonist and its main
pharmacodynamic effect is the inhibition of gastric secretion.
29) Ranitidine is a non -imidazole blocker of those histamine receptors which mediate gastric secretion (H2-receptors).