antihistamine


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Related to antihistamine: decongestant

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.

antihistamine

/an·ti·his·ta·mine/ (-his´tah-mēn) an agent that counteracts the action of histamine; usually used for agents blocking H1 receptors (H) and used to treat allergic reactions and as components of cough and cold preparations. Agents blocking H2 receptors, used to inhibit gastric secretion in peptic ulcer, are usually called H.

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.

antihistamine

[-his′təmin]
Etymology: Gk, anti + histos, tissue, amine (ammonia compound)
any substance capable of reducing the physiological and pharmacological effects of histamine, including a wide variety of drugs that block histamine receptors. Many such drugs are readily available as over-the-counter medicines for the management of allergies. Toxicity resulting from the overuse of antihistamines and their accidental ingestion by children is common and sometimes fatal. These substances do not completely stop the release of histamine, and the ways in which they act on the central nervous system are not completely understood. The antihistamines are divided into histamine1 (H1) and histamine2 (H2) blockers, depending on the responses to histamine they prevent. H1-blocking drugs, such as alkylamines, ethanolamines, ethylenediamines, and piperazines, are effective in the symptomatic treatment of acute allergies. Second-generation H1 blockers, such as cetirizine, fexofenadine, and loratadine, cause less sedation. The H2-blocking drugs are effective in the control of gastric secretions and are often used in the treatment of gastroesophageal reflux. Antihistamines can both stimulate and depress the central nervous system. antihistaminic, adj.

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.

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.

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).

antihistamine

see ALLERGY.

Antihistamine

A drug that inhibits the actions of histamine. Histamine causes dilatation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion.

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.

antihistamine (an´tīhis´təmin),

n a drug that counteracts the release of histamine such as occurs in allergic reactions; also has topical anesthetic and sedative effects, as well as a drying effect on the nasal mucosa.

antihistamine

a drug that counteracts the effects of histamine by acting on histamine receptors without activating them but preventing their accessibility to histamine. A competitive and reversible reaction. There are two types:
Those that block H1 receptors are commonly referred to as the antihistamines and are widely used to relieve the symptoms of allergic reactions, especially urticaria. Some have an antinauseant action that is useful in the prevention of motion sickness and others have a sedative and hypnotic action.
H2 receptor blocking agents inhibit the stimulation of gastric secretions.
See also histamine antagonists, H2-receptor blocker.
References in periodicals archive ?
Read the label to ensure you choose the appropriate antihistamine medication for your symptoms.
Parents should think twice before administering antihistamines to relieve their child's symptoms during their next ear infection.
Use of nonsedating antihistamines (including loratadine) and sedating antihistamines also were not associated with hypospadias.
Superiority of An Intranasal corticosteroid compared with an Oral Antihistamine in the As-Needed Treatment of Seasonal Allergic Rhinitis.
Prof Robert Davies of the British Allergy Foundation said: "Older antihistamines can make you feel drowsy, and in fact some are also sold as mild sleeping pills.
Many people who take antihistamines experience some distressing side effects: drowsiness and loss of alertness and coordination.
For example, he might take the antihistamine only at night and take the decongestant alone in the daytime.
before the meta-analysis also demonstrated that the intranasal steroid fluticasone propionate modestly reduced TNSS compared with the oral antihistamine fexofenadine (1 point vs 1.
The most common treatment for hayfever is an antihistamine, available as tablets (liquids for young children), nasal sprays and eye drops.
The researchers used self-reported data on medically diagnosed allergies and antihistamine use for 419 patents with glioma and 612 cancer-free patients from Duke University and NorthShore University HealthSystem.
With the Additional Supply (AS) legislation changes in 2005, optometrists with appropriate training may access prescription-only medicines (PoM) including mast cell stabilisers, most of the topical ocular antihistamine eye drops and a non-steroidal anti-inflammatory drug (NSAID).