antihistamine

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Related to Antihistaminergic: H1 receptor antagonist, H1 antihistamine

antihistamine

 [an″te-, an″ti-his´tah-mēn]
a drug that counteracts the effects of histamine, a normal body chemical that among its actions is believed to cause the symptoms of persons who are hypersensitive to various allergens. While the term antihistamine can broadly include any agent that blocks any histamine receptor, in practice it is usually used to denote those blocking the H1 type of receptors (H1 receptor antagonists), those involved in allergic reactions. Agents blocking the H2 type of receptors are usually called histamine H2 receptor antagonists, and include the agents used to inhibit gastric secretion in peptic ulcer.

Antihistamines are used to relieve the symptoms of allergic reactions, especially hay fever and other allergic disorders of the nasal passages. Some antihistamines have an antinauseant action that is useful in the relief of motion sickness. Others have a sedative and hypnotic action and may be used as tranquilizers. Many are ingredients of compound preparations used to treat coughs or the common cold.

Patients for whom an antihistamine has been prescribed should be instructed about the side effects of these drugs, including drowsiness, dizziness, and muscular weakness. These side effects present a special hazard in driving an automobile or operating heavy machinery. Other side effects include dryness of the mouth and throat and insomnia.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

antihistamine

(ăn′tē-hĭs′tə-mēn′, -mĭn, ăn′tī-)
n.
A drug used to counteract the physiological effects of histamine production in allergic reactions and colds.

an′ti·his′ta·min′ic (-mĭn′ĭk) adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

antihistamine

An agent that counteracts the effects of histamine released during allergic reactions by blocking histamine (H1) receptors.
 
Adverse effects
Dry mouth, drowsiness, urine retention in men, tachycardia.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.

antihistamine

Antihistaminic Pharmacology An agent that counteracts the effects of histamine released during allergic reactions by blocking histamine–H1 receptors Adverse effects Dry mouth, drowsiness, urine retention in ♂, tachycardia. See Histamine receptor.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

antihistamine

One of a group of drugs which act against histamine-a powerful and highly irritant agent released in the body by MAST CELLS, after contact with certain ALLERGENS. Antihistamine drugs fall into two groups-those that block H1 receptors and act mainly on blood vessels, and those that block H2 receptors and act mainly on the secretion of acid in the stomach. H1 receptor blockers include diphenhydramine, chlorpheniramine (chlorphenamine) (Piriton), terfenadine (Triludan), promethazine (Phenergan), cyproheptadine (Periactin), mequitazine (Primalan) and phenindamine (Thephorin). H2 receptor blockers are not usually referred to as antihistamines, although this is what they are. They include CIMETIDINE (Tagamet), and RANITIDINE (Zantac).
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

antihistamine

see ALLERGY.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

Antihistamine

A drug that inhibits the actions of histamine. Histamine causes dilatation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

antihistamine 

Any substance that reduces the effect of histamine or blocks histamine receptors, usually the histamine 1 (H1) receptor. It is used in the treatment of allergic conjunctivitis and also in the temporary relief of minor allergic symptoms of the eye. Common agents include antazoline sulfate, azelastine hydrochloride, cetirizine, chlorphenamine, emedastine, epinastine hydrochloride, ketotifen, levocabastine, loratadine and olopatadine. See hypersensitivity; mast cell stabilizers.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
APA: High-potency antipsychotics are preferable during pregnancy; they're less likely to cause anticholinergic, antihistaminergic, or hypotensive effects
For example, the antihistaminergic effects of TCAs may be used to clinical advantage in patients with comorbid neurotic dermatitis or with abdominal complaints related to acid production.[39] Tricyclic antidepressants that increase norepinephrine levels may be more efficacious in treating somatic syndromes relating to chronic pain and migraine headache.[37] Because IBS is one of the most common complaints of somatic patients with underlying psychiatric illness, patients who have predominant cramping and diarrhea may benefit from the anticholinergic properties of TCAs.
Unlike the TCAs, the SSRIs do not cause the broad spectrum of side effects that result from anticholinergic, antihistaminergic, and [alpa]-adrenergic properties.
This nonspecific mechanism of action is also responsible for the variety of side effects associated with TCA therapy, including dry mouth, constipation, blurred vision (anticholinergic effects), sedation, weight gain (antihistaminergic effects), and sexual dysfunction (serotonergic effects).[45,50] The TCAs are also extremely lethal in an overdose situation and are associated with orthostatic hypotension (with subsequent falls and fractures), cognitive dysfunction, and cardiac effects causing bundle branch or complete heart block and sudden death.[27] TCA therapy should be initiated with conservative low doses and plasma-concentration monitoring.
BDZs, BDZAs, and melatonin agonists potentiate sleeppromoting systems, while orexin antagonists and antihistaminergics suppress wakepromoting systems.