The role of histamine in allergy development

Active selection of histamine into the blood occurs in the development of any allergic reaction. Histamine is a mediator (mediator) the transmission of nerve impulses, which in normal circumstances is bound. During an allergic reaction, it acts on the sensitive receptors, and it causes bronchial spasm, lowering blood pressure, dilation of small blood vessels (capillaries), which in turn contributes to tissue edema and rashes, increased secretion of gastric juice. Severe allergic reactions due to a sharp drop in blood pressure may occur renal failure. All sensitive histamine H1 receptors are divided not responsible for reaction bronchial tissue edema and H 2 - are responsible for gastric acid secretion.

Antihistamine drugs

Any drugs which can block the histamine receptors and a histamine yield blood. Such drugs called antihistamines. H1 receptor blockers-induced histamine relieve muscle spasms of the bronchi, reduces the permeability of small blood vessels, and thus tissue swelling, prevent a sharp drop in blood pressure, make it easier for allergic reactions. H2 receptor blockers reduce gastric acid secretion and are used for diseases of the gastrointestinal tract.

What is Claritin

Claritin (INN - loratadine) - is an antihistamine, histamine H1-receptor, which provides rapid and sustained anti-allergic effect (reduces itching and swelling of the tissues, relieves muscle spasm of the bronchi).

Improvement of notes within the first 30 minutes after ingestion. Antihistamines reaches a maximum effect within 8-12 hours after the onset of action and lasts more than 24 hours.

Available Claritin pharmaceutical company Schering-Plough, USA.

Indications for use

Claritin is prescribed for the following diseases:

• allergic rhinitis (seasonal and perennial)
• allergic conjunctivitis;
• hay fever (allergy to pollen);
• bronchial asthma and asthmatic bronchitis;
• urticaria and angioedema (rash quickly, which merges and changes in tissue swelling);
• itchy allergic rash;
• allergic reactions to insect bites and other

Contraindications for use

Do not take Claritin if:

• hypersensitivity thereto;
• pregnancy, breast-feeding Breast-feeding: feed - and no nails! ;
• a child under the age of two years.

Claritin should be taken with caution in severe liver disease.

Side effects when taking Claritin

Since receiving Claritin violates all exchanges of histamine in the body, it can cause a number of side effects that occur:

• From the nervous system: fatigue, anxiety Anxiety - how to distinguish normal from disease? , Agitation, dizziness, headache, drowsiness, trembling hands, memory impairment, depression Depression - a little more than a bad mood   (depressed mood);
• on the part of the skin and subcutaneous tissue: skin inflammation;
• With the genitourinary system: micturition, menstrual disorders, vaginitis (inflammation of the vaginal mucosa);
• by metabolism Metabolism: The basis of life of all living things : Weight gain, sweating, thirst;
• on the part of the musculoskeletal system: leg cramps, pain in muscles and joints;
• From the digestive system: nausea, vomiting, dry mouth, change in taste, constipation or diarrhea, stomach pain, bloating, decrease or increase in appetite, stomatitis;
• The respiratory system: dry mucous membranes of the nose, inflammation of the sinuses, cough, sometimes - bronchospasm;
• From the senses: visual impairment, conjunctivitis, pain in the eyes and ears;
• on the part of the cardiovascular system: reduction or increase in blood pressure, palpitations;
• Allergic reactions: tissue edema, urticaria, pruritus;
• may also occur: back pain, chest, fever, chills, sore breasts.

Claritin does not cause such side effects like drowsiness and impaired concentration, therefore, does not affect performance. But potentially hazardous activities that require high concentration and speed of psychomotor reactions (eg, driving) during treatment Claritin should not be performed.

Histamine and its role in the human body

Histamine - a substance which is in an inactive form in most body tissues. Active histamine released from the exposed tissue, injury, allergic disorders or poisons. Role of histamine located on the cell membranes of the gastro-intestinal tract, respiratory system, skin is to neutralize foreign substances. Histamine located on gastric glands, intestines, lacrimal, salivary glands, is involved in the secretory process by stimulating it.

Histamine is a neurotransmitter that is an intermediary transmission of nerve impulses from nerve cells in the organs and tissues. It causes smooth muscle (muscles of internal organs and blood vessels) with the exception of smooth muscles of large arteries. It histamine causes spasm of the bronchial muscles in bronchial asthma. Small arteries dilate, which causes a decrease in blood pressure Blood pressure - dangerous if his swing? . Increased permeability of the very small blood vessels (capillaries) causes tissue swelling and blistering of the skin (urticaria and angioedema). Histamine also causes irritation and itching of the skin. With the release of large amounts of histamine, a sharp drop in blood pressure while bronchospasm (anaphylactic shock).

Histamine also stimulates gastric secretion, while the gastric juice increases the amount of acid and pepsin.

Later it was found that there are two types of histamine receptor (receptor - a special cell structure that interacts with a particular mediator, in this case with histamine):

• N1- receptors transmit vascular effects (edema, dilation of blood vessels);
• H2 receptors to transmit stimuli of gastric secretion and some cardiovascular effects.

Antihistamine drugs and their types

Once it was established that histamine release with tissue damage may have undesirable effects, searches started drugs capable of neutralizing its activity. The first drugs that block histamine receptors have been put into practice in 1947 and became known as antihistamines, they rented an increased capillary permeability, inflammation and itching.

For H2 receptors were also invented drugs that suppress their activity. Thus, histamine antagonists currently divided into N1- receptor blockers and H2 histamine receptor blockers.

Histamine receptor blockers N1-

Since their introduction in practice the number of drugs in this group is increasing all the time, and their quality improved. Antihistamines do not eliminate allergies and only reduce some of its manifestations. They usually have a lot of side effects, as other mediators receptors are located next to histamine and antihistamines also inhibit their action. So, they can cause drowsiness, dizziness, weakness, irritation of the gastrointestinal tract, dryness in the mouth. But at the moment there are a number of drugs that are almost completely devoid of side effects.

Histamine receptor blockers N1- varying degrees eliminate all the effects of histamine, apart from its influence on the gastric secretion. Eliminates the effect of leading to edema Prevention and treatment of edema - it is important to understand the root cause   fabrics, dramatic expansion of blood vessels, bronchospasm. These drugs are more effective when applied to the release of histamine, that is, before the allergic reaction.

By blockers N1- receptor antagonists are known to all such drugs like diphenhydramine, diazolin, suprastin, tavegil, klaretin and others.

Histamine H2-receptor blockers

Histamine H2- receptors are on gastric secretory cells and can be stimulated by mediators such as histamine, gastrin and acetylcholine. Feature H2 blockers - receptor antagonists is that these agents are able to block the production of gastric juice, stimulated not only histamine and other mediators. This property is very important in the treatment of diseases of the gastrointestinal tract, accompanied by increased secretion, for example, gastric ulcer.

Side effects when taking these drugs are rare. This can be a headache, rash, dizziness, Dizziness - if the ground is slipping from under his feet , Nausea, diarrhea or constipation.

For drugs in this group include cimetidine, ranitidine Ranitidine - help in the prevention of relapse of peptic ulcer , Famozidin.

Antihistamines can be a good tool in the fight against allergies and gastrointestinal diseases, but always need to remember that their mechanism of action is complex, almost always have side effects of their use, so they must appoint a doctor.