Desensitizing drugs (antiallergic, antihistamines) are drugs that have been used in the treatment of allergic conditions. The mechanism of action of such drugs is manifested in the form of blocking H1-histamine receptors. Consequently, there is a suppression of the effect of histamine - the main substance-mediator, which provides the occurrence of most allergic manifestations.
Histamine was identified from animal tissues in 1907, and by 1936 the first drugs were discovered that inhibited the effects of this substance. Repeated studies claim that it causes typical signs of allergy through its effects on the histamine receptors of the respiratory system, skin and eyes, and antihistamines can suppress this reaction.
Classification of desensitizing drugs according to the mechanism of action on different types of allergies:
• Drugs that affect the immediate type of allergic reaction.
• Drugs that affect delayed allergic reactions.
Drugs affecting immediate allergic reactions
1. Means that inhibit the release of allergic mediators from smooth muscle and basophilic cells, while inhibition of the cytotoxic cascade of the allergic reaction is observed:
• β1-agonists;
• glucocorticoid;
• Antispasmodic myotropic effects.
2. Cell membrane stabilizers.
3. Blockers of H1-histamine receptors of cells.
4. Desensitizing.
5. Complementary system inhibitors.
Medications for delayed allergic reactions
1. NSAIDs.
2. Glucocorticoid.
3. Cytostatic.
Pathogeny of Allergy
In the pathogenetic development of allergies, histamine plays a huge role, 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 presented in an inactive phase in combination 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 contribute to the penetration of Ca into the cell, the latter acting on the contraction of smooth muscles.
Acting on H2-histamine receptors, histamine activates adenylate cyclase and increases the production of cellular cAMP, this causes an increase in the secretion of the gastric mucosa. Thus, some desensitizing agents are used to reduce HCl secretion.
Histamine creates capillary expansion, increases the permeability of the walls of blood vessels, edematous reaction, a decrease in plasma volume, which leads to thickening of the blood, a decrease in pressure in the arteries, a reduction in the smooth muscle layer of the bronchi due to irritation of H1-histamine receptors; increased adrenaline release, increased heart rate.
Acting on the H1 receptors of the endothelium of the capillary wall, histamine releases prostacyclin, this contributes to the expansion of the lumen of small vessels (especially venules), the deposition of blood in them, a decrease in the volume of circulating blood, this ensures the release of plasma, proteins and blood cells through the dilated interendothelial wall space.
From the fifties of the 20th century. and until now, desensitizing drugs have been subject to repeated changes. Scientists managed 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.
First generation desensitizing drugs
1st generation desensitizers easily cross the blood-brain barrier (BBB) and bind to cortical histamine receptorsbrain. In this way, desensitizers contribute to a sedative effect, both in the form of slight drowsiness and in the form of sound sleep. Medications of the 1st generation additionally 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 a competitive action with acetylcholine, because these drugs can interact with muscarinic nerve endings, like acetylcholine. So, in addition to the calming effect, these drugs lead to dry mouth, constipation and tachycardia.
1st generation desensitizers are carefully prescribed for glaucoma, ulcers, heart disease, and in combination with antidiabetic and psychotropic drugs. They are not recommended for more than ten days due to the potential for addiction.
2nd generation desensitizers
These drugs have a very high affinity for histamine receptors, as well as a selective property, while not 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 mild drowsiness).
After you stop taking these medicines, the healing effect may remain for 7 days.
Some have an anti-inflammatory effect, a cardiotonic effect. The last disadvantage requires the control of cardiovascular activity.system at the time they are received.
3rd (new) generation desensitizers
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 justified itself in long-term antiallergic therapy - the treatment of allergic rhinitis, rhinoconjunctivitis, urticaria, dermatitis.
Desensitizing drugs for children
Antiallergic drugs for children, which belong to the group H1-blockers, or desensitizing drugs - these are drugs intended for the treatment of all kinds of allergic reactions in the child's body. Medicines are distinguished in this group:
• I generation.
• II generation.
• III generation.
Drugs for children - I generation
What are the desensitizing drugs? They are listed below:
• "Fenistil" - recommended for children older than one month in the form of drops.
• Diphenhydramine - over seven months old.
• "Suprastin" - over one year old. 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.
• "Clemastin" - older than six years of age, after 12 months. in the form of syrup and injections.
• "Tavegil" - older than six years of age, after 12 months. in the form of syrup and injections.
Drugs for children - II generation
The most common desensitizing drugs of this type are:
• Zyrtec is over six months old in drop form and over six years old in tablet form.
• Claritin is over two years old.
• Erius - over one year old in syrup form and over twelve years old in tablet form.
Drugs for children – III generation
Desensitizing drugs of this type include:
• Astemizol - over two years old.
• "Terfenadine" - over three years in suspension form and over six years in tablet form.
We hope that this article will help you navigate and make the right choice when choosing antiallergic drugs for a child's body (and not only). However, it should be noted that before using such medications, it is imperative to read the instructions, thanks to which you can deal with the question: "Desensitizing drugs - what is it?". You should also seek medical advice.
