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  • Topic: H1 antagonist, Histamine, Histamine antagonist
  • Pages : 6 (1986 words )
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  • Published : November 8, 2010
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If somebody where to ask you if you know what an antihistamine is your answer would probably be yes seeing as these drugs are well known for their allergy relief. But there is more to know about antihistamine than the fact that they help resolve your allergy problems. As the paper goes on we will be taking a closer look into antihistamines, discovering that the way antihistamines help with allergies is through their blocking action, stopping histamine from attaching to its receptor. We see that even though drowsiness is a commonly known side effect of these drugs it is mostly a side effect pertaining to what is known as first generation antihistamines; second generation antihistamines, which are the newer ones do not cause sedation or drowsiness. Even though antihistamine is a wonderful medication and serves a very important use in the medical world it still presents its disadvantages as do all drugs. In this paper we see how a very useful form of antihistamine can be used as a narcotic for recreational purposes. We also learn that antihistamines can be used for treatments other than blocking histamine; antihistamine is currently being investigated to be used as a painkiller, expanding the branch of analgesics. There is much to be learned about antihistamines and in the pages following you will be presented with some of this very useful information.

What are antihistamines?
Antihistamines are most commonly used to control the symptoms of allergies such as hay fever. Antihistamines are drugs that fight the histamine released during an allergic reaction by blocking the action of the histamine on the tissue. Antihistamines do not stop the development of histamine nor do they stop the conflict between the IgE and antigen. Therefore, antihistamines do not stop the allergic reaction but protect tissues from some of its effects. How do antihistamines work?

Antihistamines work by preventing the actions of histamine, which is a substance produced by the body as part of its natural defenses. It is stored in cells called mast cells, in almost all tissues of the body, and is released when the body reacts to a foreign substance (known as an allergen). The released histamine binds to its receptors (H-1 receptors) causing a chain reaction that includes an increase in blood flow to the area, and the release of other chemicals that add to the allergic response. Itching is one of the results. Antihistamines work by blocking histamine receptors, therefore reducing the reactions that cause itching. However, histamine is only one of many substances in the body that cause itching. Types of antihistamines

There are two different types of antihistamine, the older group, know as first generation antihistamines are sedating antihistamines, they enter the brain and cause drowsiness, while the newer non-sedating antihistamines known as second generation antihistamines do not. Many antihistamine drugs are available without a prescription. Examples include the first-generation antihistamines such as brompheniramine (Dimetapp, Bromphen, Dimetane, Nasahist), chlorpheniramine (Chlor-Trimeton), clemastine (Allerhist, Tavist), and diphenhydramine (Benadryl), and a second-generation antihistamine loratadine (Claritin). Loratadine (Claritin) does not cause drowsiness. Common prescription antihistamines (all second-generation antihistamines) include cetirizine (Zyrtec), desloratadine (Clarinex), and fexofenadine (Allegra). These antihistamines (and loratadine) are less likely to cause adverse effects like drowsiness or dry mouth. Several antihistamine nasal sprays (for example, azelastine [Astelin]) are also available to treat symptoms such as runny nose, sneezing, and itchy nose. Itching can occur during the day but is usually worse in early evening and at night, so sedating antihistamines are used because they help make you sleepy, as well as reducing the itch. Antihistamines come in tablet, chewable tablet, capsule,...
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