antihistamine

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antihistamine

(ăn'tĭhĭs`təmēn), any one of a group of compounds having various chemical structures and characterized by the ability to antagonize the effects of histaminehistamine
, organic compound derived in the body from the amino acid histidine by the removal of a carboxyl group (COOH). Although found in many plant and animal tissues, histamine is specifically important in human physiology because it is one of the chemicals released from
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. Their principal use in medicine is in the control of allergies such as hay fever and hives. Some antihistamines are also useful as sedatives and for the prevention of motion sickness; others, such as fexofenadine (Allegra) and loratadine (Claritin) are nonsedating.

Antihistamine

A type of drug that inhibits the combination of histamine with histamine receptors. These drugs are termed either H-1 or H-2 receptor antagonists depending on which type of histamine receptor is involved. H-1 receptor antagonists are used largely for treating allergies, and H-2 receptor antagonists are used to treat peptic ulcer disease and related conditions. See Histamine

The primary therapeutic use of H-1 receptor antagonists is to antagonize the effects of histamine released from cells by antigen-antibody reactions; they can thus inhibit histamine-induced effects, such as bronchoconstriction, skin reactions, for example, wheals and itching, and nasal inflammation. These drugs, therefore, are quite effective in reducing allergy signs and symptoms, especially if they are administered before contact with the relevant antigen; however they are not effective in treating asthma. Their effects vary widely, both among the drugs and from individual to individual; in young children excitement may be seen. Another common set of effects caused by many of these drugs, including dry mouth, blurred vision, and urinary retention, can be ascribed to their anticholinergic actions. H-1 receptor antagonists have low toxicity. The chief adverse effect is sedation. Overdoses of H-1 receptor antagonists may be associated with excitement or depression, and although there is no pharmacologic antidote for these drugs, good supportive care should be adequate in managing cases of poisoning. See Allergy, Antigen-antibody reaction

H-2 receptor antagonists are much newer. Histamine stimulates gastric acid secretion by combining with H-2 receptors. By preventing this combination, H-2 antagonists can reduce acid secretion in the stomach, an effect that makes these drugs useful in managing various conditions, such as peptic ulcer disease.

Other conditions in which H-2 antagonists are used to lower gastric acidity include reflux esophagitis, stress ulcers, and hypersecretory states such as the Zollinger-Ellison syndrome, in which tumor cells secrete large amounts of the hormone gastrin, which stimulates gastric acid secretion. In these conditions, administration of H-2 antagonists reduces symptoms and promotes healing.

The toxicity of H-2 antagonists is quite low, and adverse effects are reported by only 1-2% of patients. The most common side effects are gastrointestinal upsets, including nausea, vomiting, and diarrhea.

antihistamine

[‚an·tē′hist·ə‚mēn]
(pharmacology)
A drug that prevents or diminishes the effect of histamine; used in treating allergic reactions and common-cold symptoms.

antihistamine

any drug that neutralizes the effects of histamine, used esp in the treatment of allergies
References in periodicals archive ?
"I've tried anti-histamines, steroid creams, evening primrose and all sorts of moisturisers - but usually nothing will calm the itchiness down except getting into a cool bath.
In most cases, an anti-histamine treatment is prescribed.
Twelve of those children were provided with anti-histamine medication while two cases required Epi Pen jabs which are required for severe allergic reactions.
"Whilst in some cases it may be necessary to see a doctor, especially if the symptoms persist, there are many anti-histamine medications that can be bought over the counter at your pharmacist that should provide effective relief.
Anti-histamine with Adrenaline###9 (23.7%)###11 (30.5%)
The second type of heatstroke occurs in adults, patients with chronic diseases, sedate persons, alcoholics, obese persons, elderly persons or patients who take anti-histamine drugs or anti-depressants, as well as persons who consume excessive quantity of coffee and/or tea.
Bring your darkest sun glasses, a hat, and a non-sleepy anti-histamine. Wine country has lots of pollen, yeast and mold.
Quercetin is a natural anti-histamine found in apples, citrus fruits and tea, so include them in your diet.
If this occurs, anti-histamine tablets (available at pharmacies without a prescription) will help.
The participants were also apprised about the latest research and techniques in the treatment of allergy patients and provision of effective anti-histamine medicines and appropriate use of nebulizers and inhalers by the patients.
The sufferers should acquire anti-histamine available over the counter at most pharmacies.
Gaza's 1.5 million Palestinians have been suffering the effects of a crippling Israeli blockade since the Hamas movement took full control of the territory after pushing out security forces loyal to Mahmoud Abbas, the Palestinian president, in June 2007.Since then there have been shortages of basic necessities such as food, fuel and medicines as Israel has strictly controlled all deliveries.Medicine shortagesLast week, the International Committee of the Red Cross said that virtually no medical supplies were reaching the Gaza Strip, putting the lives of several hundred patients at risk."We got a list of zero stock medicines in Gaza, like baby formula, paracetamol, anti-histamine tablets," Ibrahim Hamami, a Palestinian-Briton and family physician from Buckinghamshire, said.