Which among the following is a H2 receptor blocker?
Cimetidine was the first H2 receptor antagonist used for the treatment of acid peptic disorders. Cimetidine may have weak anti androgenic side effects resulting in reversible gynecomastia and impotence, primarily in patients receiving high doses for prolonged periods of time. H2 receptor blockers like cimetidine, ranitidine, and famotidine inhibit gastric acid secretion but otherwise share no effects with H1 agents, do not produce significant intoxication. Also Know: Cetirizine have competitive antagonism/inverse agonism at H1 Receptors. It reduces or prevents histamine effects on smooth muscle, immune cells. It is clinically applied for IgE immediate allergies, especially hay fever, uicaria. Ethylenediamines (Prototype: Pyrilamine): These include some of the most specific H1 antagonists. Although their central effects are relatively feeble, somnolence occurs in a fair propoion of patients. GI side effects are quite common. Atropine sulfate, a naturally occurring antimuscarinic drug, competitively antagonizes the effects of acetylcholine and other muscarinic agents. It increases sinus node automaticity and AV conduction by blocking vagal activity. It thus has been termed a parasympatholytic drug. Ref: Skidgel R.A., Erdos E.G. (2011). Chapter 32. Histamine, Bradykinin, and Their Antagonists. In L.L. Brunton, B.A. Chabner, B.C. Knollmann (Eds), Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12e.
Cimetidine
Cetirizine
Pyrilamine
Atropine