antihistamine

(redirected from loratadine)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.

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
..... Click the link for more information.
. 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 ?
Comparison of intranasal triamcinolone acetonide with oral loratadine in the treatment of seasonal ragweed-induced allergic rhinitis.
Also, pollen levels are highest in the morning, so loratadine and cetirizine will be well absorbed into your child's system and ready for battle if taken at bedtime (a good deal if pollen is your child's major "invader").
fexofenadine is indicated for use in children aged 6 years and older, loratadine for children 2 years or older, cetirizine for children 6 months and older, and azelastine for children 5 years and older.
Eleven cases and 22 controls were exposed to loratadine anytime from 1 month before pregnancy through the first 3 months of gestation.
The uncertainty regarding the reproductive safety of loratadine was complicated by the publication of a retrospective analysis from Sweden in 2002 suggesting that the risk of hypospadias in babies exposed in utero to loratadine was twice that of the general population.
Pregnancy outcomes were similar among the 161 women who took loratadine during the first trimester (a mean total dose of 159.
Exposure was defined as any maternal use of loratadine from 1 month before pregnancy through the first trimester.
Loratadine was significantly more effective than placebo for most end points, except for nighttime symptoms and non-nose/non-eye symptoms.
Loratadine and astemizole significantly boosted the growth of both melanoma and fibrosarcoma, and hydroxyzine promoted the development of just melanoma.
For medicinal products to be designated by the bidder closer to the active substance Loratadine, ATC R06AX13, the DAK-G intends to conclude drug discounts with the most possible pharmaceutical companies as soon as new pharmaceutical contract deals enter into force.
They compared the prices to cures under the drug names of paracetamol, ibuprofen, loratadine, cetirizine, loperamide and fluconazole.