/an'ti his"teuh meen', -min/, n. Biochem., Pharm.
any of certain compounds or medicines that neutralize or inhibit the effect of histamine in the body, used chiefly in the treatment of allergic disorders and colds.
[1930-35; ANTI- + HISTAMINE]

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Synthetic drug that counteracts the effects of released histamine in the body.

Antihistamines compete with histamine at one of the three types of histamine receptors, preventing allergic attacks (see allergy) or inflammation. Some antihistamines also prevent motion sickness and vertigo. Drowsiness is a frequent side effect. H2 antihistamines, which bind to the second receptor type, are used to control gastric-acid secretion (see stomach) and treat peptic ulcers.

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      any of a group of synthetic drugs that selectively counteract the pharmacological effects of histamine (q.v.), following its release from certain large cells (mast cells) within the body. Antihistamines replace histamine at one or the other of the two receptor sites at which it becomes bound to various susceptible tissues, thereby preventing histamine-triggered reactions under such conditions as stress, inflammation, and allergy.

      The antihistamines that were the first to be introduced are ones that bind at the so-called H1 receptor sites; they are therefore designated H1-blocking agents and oppose selectively all the pharmacological effects of histamine except those on gastric secretion. The development of these antihistamines dates from about 1937, when French researchers discovered compounds that protected animals against both the lethal effects of histamine and those of anaphylactic shock. The first antihistamines were derivatives of ethylamine; aniline-type compounds, tested later and found to be more potent, were too toxic for clinical use. In 1942, the forerunner of most modern antihistamines (an aniline derivative called Antergan) was discovered; subsequently, compounds that were more potent, more specific, and less toxic were prepared. More than 100 antihistaminic compounds soon became available for treating patients.

      Since histamine is involved in the production of some symptoms of allergy and anaphylaxis, antihistamines can control certain allergic conditions, among them hay fever and seasonal rhinitis; the nasal irritation and watery discharge are most readily relieved. Persons with urticaria, edema, itching, and certain sensitivity reactions respond well. Antihistamines are not usually beneficial in treating the common cold and asthma. Antihistamines with powerful antiemetic properties are used in the treatment of motion sickness and vomiting. Used in sufficiently large doses, nearly all antihistamines produce undesirable side effects; the incidence and severity of the side effects depend both on the patient and on the properties of the specific drug. The most common side effect in adults is drowsiness. Other side effects include gastrointestinal irritation, headache, blurred vision, and dryness of the mouth. If a patient's condition does not improve after three days of treatment with antihistamines, it is unlikely that he will benefit from them. Antihistamines are readily absorbed from the alimentary tract, and most are rendered inactive by monoamine oxidase enzymes in the liver.

      During the 1970s an H2-blocking agent, cimetidine (Tagamet) was introduced. Compounds of this class suppress histamine-induced gastric secretion and have proved extremely useful in treating gastric and duodenal ulcers.

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Universalium. 2010.

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Look at other dictionaries:

  • antihistamine — (n.) 1933, from ANTI (Cf. anti ) + HISTAMINE (Cf. histamine) …   Etymology dictionary

  • antihistamine — ► NOUN ▪ a drug that counteracts the effects of histamine, used in treating allergies …   English terms dictionary

  • antihistamine — [an΄tī his′tə mēn΄; an΄tēhis′tə mən, an΄tihis′tə mēn; an΄tī his′təmin΄, an΄tē his′təmin΄, an΄ti his′təmin΄] n. any of several synthetic drugs used to minimize or prevent the action of histamine, as in an allergic condition antihistaminic… …   English World dictionary

  • antihistamine — an·ti·his·ta·mine .ant i his tə .mēn, .an .tī , mən adj tending to block or counteract the physiological action of histamine <human blood lacks antihistamine activity> antihistamine n any of various compounds that oppose the actions of… …   Medical dictionary

  • antihistamine — UK [ˌæntɪˈhɪstəmiːn] / US [ˌæntɪˈhɪstəˌmɪn] noun [countable/uncountable] Word forms antihistamine : singular antihistamine plural antihistamines medical a drug used to treat an allergy (= a bad reaction to something you swallow or touch) …   English dictionary

  • antihistamine — noun Date: 1946 any of various compounds that counteract histamine in the body and that are used for treating allergic reactions (as hay fever) and cold symptoms • antihistamine adjective • antihistaminic adjective or noun …   New Collegiate Dictionary

  • antihistamine — [[t]æ̱ntihɪ̱stəmɪn[/t]] antihistamines also anti histamine N COUNT An antihistamine is a drug that is used to treat allergies …   English dictionary

  • antihistamine —    An exogenous agent that inhibits the release of histamine, the amino acid derivative that stimulates vasodilation and permeability under many circumstances, particularly tissue irritation. The most common type of antihistamine, the H1 receptor …   Herbal-medical glossary

  • antihistamine — noun A drug or substance that counteracts the effects of a histamine. Commonly used to alleviate the symptoms of hay fever and other allergies …   Wiktionary

  • antihistamine — an|ti|his|ta|mine [ˌæntıˈhıstəmi:n, mın] n [U and C] a drug that is used to treat an ↑allergy (=an unpleasant reaction to particular foods, substances etc) …   Dictionary of contemporary English

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