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 H 1 type of receptors (H 1 receptor antagonists ), those involved in allergic reactions. Agents blocking the H 2 type of receptors are usually called histamine H 2 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.
/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.
(ăn′tē-hĭs′tə-mēn′, - mĭn, ăn′tī-)
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.
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 histamine 1 (H 1 ) and histamine 2 (H 2 ) blockers, depending on the responses to histamine they prevent. H 1 - blocking drugs, such as alkylamines, ethanolamines, ethylenediamines, and piperazines, are effective in the symptomatic treatment of acute allergies. Second-generation H 1 blockers, such as cetirizine, fexofenadine, and loratadine, cause less sedation. The H 2 - 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.
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.
Antihistaminic Pharmacology An agent that counteracts the effects of histamine released during allergic reactions by blocking histamine–H 1 receptors Adverse effects Dry mouth, drowsiness, urine retention in ♂, tachycardia. See Histamine receptor.
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 H 1 receptors and act mainly on blood vessels, and those that block H 2 receptors and act mainly on the secretion of acid in the stomach. H 1 receptor blockers include diphenhydramine, chlorpheniramine (chlorphenamine) (Piriton), terfenadine (Triludan), promethazine (Phenergan), cyproheptadine (Periactin), mequitazine (Primalan) and phenindamine (Thephorin). H 2 receptor blockers are not usually referred to as antihistamines, although this is what they are. They include CIMETIDINE (Tagamet), and RANITIDINE (Zantac).
A drug that inhibits the actions of histamine. Histamine causes dilatation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion.
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.
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 H 1 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.
H 2 receptor blocking agents inhibit the stimulation of gastric secretions.
References in periodicals archive ?
Effect of medications on symptoms of allergic rhinitis Symptoms Sneezing Rhinorrhoea Nasal Itching Ocular obstuction symptoms Intranasal +++ +++ +++ +++ ++ steroids Oral +++ +++ -- +++ + antihistamines Intranasal + + -- + -- antihistamines Intranasal -- -- +++ decongestants Anticholinergics -- +++ Leukotriene + + ++ ?
10,17) While only slight pupil dilation has been measured with the use of combination products (with an antihistamine ), (18,19) an additive effect might be due to mild cholinergic blocking actions of the antihistamine .
For instance, oral antihistamines. because of the time required for absorption, are not good options necessarily if you're going to be taking the medication just prior to exposure," he said.
1] occupancy by antihistamines and in demonstrating that this measurement correlates with the.
Continue taking the antihistamine and NSAID every 12 hours until the cold symptoms clear (3 to 7 days).
Antihistamines were first discovered by Staub and Bovet (9) at the Louis Pasteur Institute in 1937; the first clinically useful antihistamine. phenbenzamine, became commercially available in the 1940s.
Take preventative action by taking antihistamines two to three weeks prior to the onset of hay fever season
UCB has built a successful antihistamine franchise worldwide and we are optimistic about the opportunity UCB has to expand it with the introduction of levocetirizine in the U.
There is also an antihistamine liquid which is great for children.
While the label doesn't always indicate it, what you want to reach for is an antihistamine .
Although pyrilamine is an over-the-counter antihistamine. it's premature to say that people taking antihistamines for allergies may have trouble regulating their body temperature in heat stress, Wong cautions.
For that reason, UTMB researchers tested their theory that the use of an antihistamine or a corticosteroid--which is given to tamp down the immune system's response and thus reduce inflammation--would fight off the infections better.