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 ?
Promethazine, diphenhydramine, desloratadine, levocetirizine and loratadine with purity greater than 98.34% were offered by Eros Pharmaceutical Pvt.
Loratadine, Desloratadine (already approved) and Montelukast (new approval).
"We don't think Cetirizine and Loratadine work any differently so it is a matter of preference.
The data of 24 patients could be collected fully until the end of the study and were evaluated accordingly (acupuncture group: n = 15 and loratadine group: n = 9).
National Birth Defects Prevention Study found no association between loratadine and hypospadias (MMWR 2004;53:219-21).
A meta-analysis of 11 RCTs (1317 patients, average age 32) showed no significant difference in relief of eye symptoms between oral antihistamines (dexchlorpheniramine, terfenadine, and loratadine) and intranasal steroids (budesonide, beclomethasone, fluticasone, and triamcinolone) in patients with seasonal allergies, as measured by various symptom scores?
Standard-issue diphenhydramine, loratadine, and cetirizine are all effective in treating your child's allergies no matter what the cause or time of year!
The FDA approved Children's Claritin Grape Chewable Tablets (loratadine 5 mg) for temporary relief of symptoms due to hay fever or other upper respiratory allergies: runny nose; sneezing; itchy, watery eyes; and itching of the nose and throat.
The second-generation agents--fexofenadine, loratadine, cetirizine, and azelastine were developed in recent years to reduce these side effects.
But the authors said cost was the main motive behind the recent switching of two other drugs omeprazole in Sweden and loratadine in the US.
If sedation becomes problematic, loratadine (Claritin) and cetirizine are low-risk agents in pregnancy and may be considered, particularly after the first trimester.
In 2002, a study in Sweden noted that among male infants born to women who while pregnant had taken loratadine (Claritin[R]), a nonsedating antihistamine commonly used for seasonal allergies, hypospadias prevalence was twice that of the general population (1).