Desensitizing drugs (antiallergic, antihistamines) - drugs that have been used in the treatment of allergic conditions. The mechanism of action of such agents is manifested in the form of blocking H1-histamine receptors. Consequently, there is a suppression of the effects of histamine - the main mediator substance, which provides the occurrence of most allergic manifestations.
Histamine was detected from animal tissues in 1907, and by 1936 the first drugs were discovered that depressed the effect of this substance. Repeated studies claim that through exposure to histamine receptors of the respiratory system, skin and eyes, it causes typical signs of allergy, and antihistamines can suppress this reaction.
Classification of desensitizing drugs according to the mechanism of action on different types of allergies:
• Means that affect an allergic reaction of an immediate type.
• Means that affect the allergic reaction of a delayed type.
Means that affect an immediate allergic reaction
1. Means that inhibit the release of allergic mediators from smooth muscle and basophil cells, while inhibition of the cytotoxic cascade of an
allergic reaction is observed:
• β1-adrenomimetic drugs;
• glucocorticoid;
• antispasmodic myotropic effects.
2. Stabilizers of cell membranes.
3. Blockers of H1-histamine cell receptors.
4. Desensitizing.
5. Inhibitors of the complementary system.
Agents for delayed-type allergic reaction
1. NSAIDs.
2. Glucocorticoid.
3. Cytostatic.
Allergy Pathogenesis
In the pathogenetic development of allergies, a huge role is played by histamine, synthesized from histidine and deposited in basophils (mast cells) of the body's connective tissues (including blood), in platelets, eosinophils, lymphocytes and biofluids. Histamine in cells is present in the deactive phase in conjunction with proteins and polysaccharides. It is released due to a mechanical cellular defect, immune reactions, under the influence of chemicals and drugs. Its inactivation occurs with the help of histaminase from the mucous tissue. By activating H1 receptors, it excites membrane phospholipids. Due to chemical reactions, conditions are created that facilitate the penetration of Ca into the cell, the latter acting on the smooth muscle contraction.
Acting on H2-histamine receptors, histamine activates adenylate cyclase and increases the production of cell cAMP, which causes an increase in the secretion of the gastric mucosa. Thus, some desensitizing agents are used to reduce HCl secretion.
Histamine creates capillary expansion, enhances vascular wall permeability, edematous reaction, decrease in plasma volume, which leads to blood thickening, pressure reduction in arteries, reduction of the smooth muscle layer of the bronchi due to irritation of H1-histamine receptors; increased release of adrenaline, increased heart rate.
By acting on the H1 receptors of the endothelium of the capillary wall, histamine releases prostacyclin, this helps to expand the lumen of small vessels (especially venules), deposit blood in them, decrease the volume of circulating blood, this ensures the release of plasma, proteins and blood cells through the expanded interendothelial space of the walls.
Since the fifties of the 20th century. and to date, desensitizing drugs have been subject to repeated changes. Scientists were able to create new drugs with a smaller list of adverse reactions and greater effectiveness. At the present stage, there are 3 main groups of antiallergic drugs: first, second and third generation.
Desensitizing drugs of the first generation
1st generation desensitizing agents easily pass through the blood-brain barrier (BBB) and are connected with the histamine receptors of the cerebral cortex. These desensitizers contribute to sedation, both in the form of slight drowsiness, and in the form of sound sleep. 1st generation medicines further affect the psychomotor reactions of the brain. For the same reason, their use is limited in different groups of patients.
An additional negative point is also the competitive effect with acetylcholine, because these drugs can interact with muscarinic nerve endings, as well as acetylcholine. So, in addition to a calming effect, these drugs lead to dry mouth, constipation and tachycardia.
Desensitizers of the 1st generation are carefully prescribed for glaucoma, ulcers, heart diseases, and in combination with antidiabetic and psychotropic drugs. They are not recommended for taking more than ten days due to their ability to become addictive.
2nd generation desensitizing agents
These drugs have a very high affinity for histamine receptors, as well as a selective property, without affecting muscarinic receptors. In addition, they are characterized by low penetration through the BBB and are not addictive, do not produce a sedative effect (sometimes some patients may experience slight drowsiness).
At the end of taking these medicines, the therapeutic effect may remain for 7 days.
Some have anti-inflammatory effects, cardiotonic effect. The last drawback requires monitoring the activity of the cardiovascular system during their administration.
Desensitizing agents of the 3rd (new) generation
New generation desensitizing drugs are characterized by high selectivity for histamine receptors. They do not cause sedation and do not affect the functioning of the heart and blood vessels.
The use of these drugs has paid off with prolonged anti-allergic therapy - the treatment of allergic rhinitis, rhinoconjunctivitis, urticaria, dermatitis.
Desensitizing drugs for children
Antiallergic drugs for children that belong to the H1-blocker group, or desensitizing drugs, are medicines intended for the treatment of all kinds of allergic reactions in the children's body. In this group, medications are distinguished:
• I generation.
• II generation.
• III generation.
Preparations for children - I generation
What are desensitizing drugs? A list of them is presented below:
• Fenistil - recommended for children older than one month in the form of drops.
• "Diphenhydramine" - older than seven months.
• Suprastin - older than one year. Up to a year are prescribed exclusively in the form of injections, and exclusively under the medical supervision of a doctor.
• Fenkarol - over three years old.
• "Diazolin" - over two years of age.
• "Clemastine" - over six years of age, after 12 months. in the form of syrup and injection.
• "Tavegil" - older than six years of age, after 12 months. in the form of syrup and injection.
Preparations for children - II generation
The most common desensitizing drugs of this type:
• "Zirtek" - older than six months in the form of a drop and older than six years in tablet form.
• Claritin - over two years old.
• "Erius" - older than one year in the form of syrup and over twelve years in tablet form.
Preparations for children - III generation
Desensitizing drugs of this type include:
• Astemizole - over two years old.
• "Terfenadine" - older than three years in suspension and older than six years in tablet form.
We hope that this article, when selecting anti-allergic drugs for the child’s body (and not only), will help you orient yourself and make the right choice. However, it should be noted that before using such medications, it is necessary to familiarize yourself with the instructions, thanks to which you can deal with the question: "Desensitizing drugs - what is it?". You should also seek medical advice.