Hj-receptor antagonists

Another antiulcer histamine Hj receptor antagonist containing a thiazole moiety is zalb-dine (131) Its synthesis can be accomplished readily by brominating 4 acetyl 2 methylimidazole (129) to give haloketone 130 Displacement with amidinothiourea completes the synthesis of zaltidme (131) via a displacement cyclodehydration sequence [45]... 

Studies of the histamine Hj-receptor antagonists substances were extracted from 97... 

Histamine Mast cells Activation Hj receptor antagonists (e.g., diphenhydramine chloride, Benadryl )... 

Histamine Hj receptor Antagonist Acute (central nervous system) Sedation Diphenhydramine27... 

Fujikura T, Shimosawa T, Yakuo I Regulatory effect of histamine Hj receptor antagonist on the expression of messenger RNA encoding CC chemokines in the human nasal mucosa. J Allergy Chn Immunol 2001 107 123-128. 

Hj-receptor antagonists almost completely block secretion of hydrochloric acid in the stomach in response to most stimuli. These drugs play a major role in treating stomach ulcers associated with hypersecretion, because they have the ability to reduce both the volume of stomach secretion and overall acidity as well as pepsin activity. 

Hj-receptor antagonists reversibly and competitively inhibit histamine action on H2 receptors. They are pure antagonists since they do not affect Hj receptors, j3-adrenorecep-tors, or muscarinic receptors. 

Hydroxyzine hydrochloride Atarax, Vistarit) is the antihistamine with the greatest use in the treatment of anxiety. It is often used to reduce the anxiety that is associated with anesthesia and surgery. It also produces sedation, dries mucous membranes (via an anticholinergic mechanism), and has antiemetic activity. A more extensive discussion of the pharmacology of the Hj-receptor antagonists is found in Chapter 38. 

The most common use of the Hj-receptor antagonists is for the relief of allergic reactions such as rhinitis and urticaria. These compounds are also used to prevent mo-... 

The tricychc tertiary amine doxepin Zonalon, Prudox), a potent Hj- and Hj-receptor antagonist, is indicated for the short-term relief of pruritus associated with topical eczematous dermatitis. Systemic absorption occurs, and the drug may potentiate or alter the metabolism of a va-... 

Do not take tab with antacids or Hj-receptor antagonists separate doses by at least 2 hr... 

Verongula gigantea Hyatt, Verongida, Porif. verongamine (bromotyrosine metabolite)/histamine Hj receptor antagonist Mierzwa 1994... 

The Clinical-Molecular Interface The Many Uses and Abuses of Hj Receptor Antagonists... 

Hj receptor antagonists (antihistamines) are among the most widely used therapeutic agents. Indeed, sometimes the exact same molecule (e.g., diphenhydramine) is marketed in different aisles in the same pharmacy under many brand names for different... 

The contraction of smooth muscle, increase in vascular permeability and mucus secretion are mediated by H receptors and is associated with increase in intracellular cyclic GMP. These type of effects are competitively blocked by Hj receptor antagonists (antihistaminics) like mepyramine. 

Fixed dose combination of histamine Hj-receptor antagonists with antacids except for those combinations approved by the Drugs Controller, India. 

Terfenadine was introduced into the marketplace as the first nonsedating histamine-1 (Hj) receptor antagonist. It was launched in the United States in 1985 under the brand name Seldane . Its patent protection was near expiration when the drug was voluntarily withdrawn from the antihistamine market in 1997. 

Nauta WTh, Rekker RF. Structure-activity relationships of Hj receptor antagonists. In Histamine and anti-Histami-nics. II, Handbook of Experimental Pharmacology. Rocha a Silva M (Ed.). Springer, Berlin, 1978, p. 215. 

Histamine Hj-receptor antagonists bind to Hj receptors without activating them, preventing histamine binding and action. They are more effective in preventing the histamine response than in reversing it. 

The superiority of omeprazole-like irreversible HVK -ATPase inhibitors over H2-receptor antagonists in acid-related disorders of the upper gastrointestinal tract is quite obvious. Their clinically relevant advantages are related to their different mode of action which is independent of the kind of acid stimulation and to their longer duration of action. Reversible H /K -ATPase inhibitors share the secretagogue independent mode of action with the irreversible inhibitors but show a duration of action which is comparable with that of Hj-receptor antagonists. Their clinical advantage over irreversible inhibitors has still to be proven. Other H /K -ATPase inhibitors such as Cl channel blockers are, at present, of experimental interest only. 

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