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Antihistamines - generations, principles of action, review of drugs. Top effective antihistamines of the new generation Suprastin what generation

Historically, the term “antihistamines” refers to drugs that block H1-histamine receptors, and drugs that act on H2-histamine receptors (cimetidine, ranitidine, famotidine, etc.) are called H2-histamine blockers. The former are used to treat allergic diseases, the latter are used as antisecretory agents.

Histamine, this most important mediator of various physiological and pathological processes in the body, was chemically synthesized in 1907. Subsequently, it was isolated from animal and human tissues (Windaus A., Vogt W.). Even later, its functions were determined: gastric secretion, neurotransmitter function in the central nervous system, allergic reactions, inflammation, etc. Almost 20 years later, in 1936, the first substances with antihistamine activity were created (Bovet D., Staub A.). And already in the 60s, the heterogeneity of histamine receptors in the body was proven and three of their subtypes were identified: H1, H2 and H3, differing in structure, localization and physiological effects that occurs during their activation and blockade. From this time on, an active period of synthesis and clinical testing of various antihistamines.

Numerous studies have shown that histamine, acting on receptors in the respiratory system, eyes and skin, causes characteristic allergy symptoms, and antihistamines that selectively block H1-type receptors are able to prevent and relieve them.

Most of the antihistamines used have a number of specific pharmacological properties, characterizing them as separate group. These include the following effects: antipruritic, decongestant, antispastic, anticholinergic, antiserotonin, sedative and local anesthetic, as well as the prevention of histamine-induced bronchospasm. Some of them are caused not by histamine blockade, but by structural features.

Antihistamines block the effect of histamine on H1 receptors through the mechanism of competitive inhibition, and their affinity for these receptors is much lower than that of histamine. Therefore, these drugs are not able to displace the histamine bound to the receptor; they only block unoccupied or released receptors. Accordingly, H1 blockers are most effective in preventing allergic reactions immediate type, and in case of a reaction, the release of new portions of histamine is prevented.

In my own way chemical structure most of them are fat-soluble amines, which have a similar structure. The core (R1) is represented by an aromatic and/or heterocyclic group and is linked via a nitrogen, oxygen or carbon molecule (X) to the amino group. The core determines the severity of antihistamine activity and some of the properties of the substance. Knowing its composition can predict the strength of the drug and its effects, such as its ability to penetrate the blood-brain barrier.

There are several classifications of antihistamines, although none of them is generally accepted. According to one of the most popular classifications, antihistamines, based on the time of creation, are divided into first and second generation drugs. First generation drugs are also commonly called sedatives (based on the dominant side effect), in contrast to non-sedating second generation drugs. Currently, it is customary to distinguish the third generation: it includes fundamentally new drugs - active metabolites, which, in addition to the highest antihistamine activity, exhibit the absence sedative effect and cardiotoxic effects characteristic of second-generation drugs (see table).

In addition, according to their chemical structure (depending on the X-bond), antihistamines are divided into several groups (ethanolamines, ethylenediamines, alkylamines, derivatives of alphacarboline, quinuclidine, phenothiazine, piperazine and piperidine).

First generation antihistamines (sedatives). All of them are highly soluble in fats and, in addition to H1-histamine, also block cholinergic, muscarinic and serotonin receptors. Being competitive blockers, they reversibly bind to H1 receptors, which leads to the use of quite high doses. The following pharmacological properties are most characteristic of them.

The sedative effect is determined by the fact that most first-generation antihistamines, easily soluble in lipids, penetrate well through the blood-brain barrier and bind to H1 receptors in the brain. Perhaps their sedative effect consists of blocking central serotonin and acetylcholine receptors. The degree of manifestation of the first generation sedative effect varies among different drugs and at different patients from moderate to severe and increases when combined with alcohol and psychotropic drugs. Some of them are used as sleeping pills (doxylamine). Rarely, instead of sedation, psychomotor agitation occurs (more often in the average therapeutic doses in children and highly toxic in adults). Because of the sedative effect, most medications should not be used while performing tasks that require alertness. All first-generation drugs potentiate the effect of sedatives and hypnotics, narcotic and non-narcotic analgesics, monoamine oxidase inhibitors and alcohol.
The anxiolytic effect characteristic of hydroxyzine may be due to suppression of activity in certain areas of the subcortical region of the central nervous system.
Atropine-like reactions associated with the anticholinergic properties of drugs are most typical for ethanolamines and ethylenediamines. Manifested by dry mouth and nasopharynx, urinary retention, constipation, tachycardia and visual impairment. These properties ensure the effectiveness of the drugs under discussion for non-allergic rhinitis. At the same time, they can increase obstruction when bronchial asthma(due to an increase in sputum viscosity), cause exacerbation of glaucoma and lead to bladder outlet obstruction in prostate adenoma, etc.
The antiemetic and anti-motion sickness effect is also likely associated with the central anticholinergic effect of the drugs. Some antihistamines (diphenhydramine, promethazine, cyclizine, meclizine) reduce the stimulation of vestibular receptors and inhibit the function of the labyrinth, and therefore can be used for movement disorders.
A number of H1-histamine blockers reduce the symptoms of parkinsonism, which is due to the central inhibition of the effects of acetylcholine.
The antitussive effect is most characteristic of diphenhydramine; it is realized through a direct effect on the cough center in the medulla oblongata.
The antiserotonin effect, primarily characteristic of cyproheptadine, determines its use for migraine.
The alpha1-blocking effect with peripheral vasodilation, especially inherent in phenothiazine antihistamines, can lead to a transient decrease in blood pressure in sensitive persons.
A local anesthetic (cocaine-like) effect is characteristic of most antihistamines (occurs due to a decrease in membrane permeability to sodium ions). Diphenhydramine and promethazine are stronger local anesthetics than novocaine. At the same time, they have systemic quinidine-like effects, manifested by prolongation of the refractory phase and the development of ventricular tachycardia.
Tachyphylaxis: a decrease in antihistamine activity with long-term use, confirming the need to alternate medications every 2-3 weeks.
It should be noted that first-generation antihistamines differ from the second generation in their short duration of action with a relatively rapid onset of clinical effect. Many of them are available in parenteral forms. All of the above, as well as low cost, determine the widespread use of antihistamines today.

Moreover, many of the qualities that were discussed allowed the “old” antihistamines to occupy their niche in the treatment of certain pathologies (migraine, sleep disorders, extrapyramidal disorders, anxiety, motion sickness, etc.) not related to allergies. Many first-generation antihistamines are included in combination medications used for colds, as sedatives, hypnotics and other components.

The most commonly used are chloropyramine, diphenhydramine, clemastine, cyproheptadine, promethazine, fenkarol and hydroxyzine.

Chloropyramine(Suprastin) is one of the most widely used sedative antihistamines. It has significant antihistamine activity, peripheral anticholinergic and moderate antispasmodic effects. Effective in most cases for the treatment of seasonal and year-round allergic rhinoconjunctivitis, Quincke's edema, urticaria, atopic dermatitis, eczema, itching of various etiologies; in parenteral form - for the treatment of acute allergic conditions requiring emergency care. Provides a wide range of therapeutic doses used. It does not accumulate in the blood serum, therefore it does not cause an overdose with long-term use. Suprastin is characterized by a rapid onset of effect and short duration (including side effects). In this case, chloropyramine can be combined with non-sedating H1-blockers in order to increase the duration of the antiallergic effect. Suprastin is currently one of the best-selling antihistamines in Russia. This is objectively due to the proven high efficiency, controllability of its clinical effect, the availability of various dosage forms, including injectable ones, and low cost.

Diphenhydramine(Diphenhydramine) is one of the first synthesized H1 blockers. It has fairly high antihistamine activity and reduces the severity of allergic and pseudo-allergic reactions. Due to its significant anticholinergic effect, it has an antitussive, antiemetic effect and at the same time causes dryness of the mucous membranes and urinary retention. Due to its lipophilicity, Diphenhydramine produces pronounced sedation and can be used as a hypnotic. It has a significant local anesthetic effect, as a result of which it is sometimes used as an alternative in cases of intolerance to novocaine and lidocaine. Diphenhydramine is available in various dosage forms, including for parenteral use, which determined its widespread use in emergency therapy. However, a significant range side effects, the unpredictability of consequences and effects on the central nervous system require increased attention when using it and, if possible, the use of alternative means.

Clemastine(Tavegil) is a highly effective antihistamine, similar in action to diphenhydramine. It has high anticholinergic activity, but penetrates the blood-brain barrier to a lesser extent, which is responsible for the low frequency of observation of sedation - up to 10%. Also exists in injection form, which can be used as an additional remedy for anaphylactic shock And angioedema, for the prevention and treatment of allergic and pseudoallergic reactions. However, hypersensitivity to clemastine and other antihistamines with similar chemical structure.

Dimetenden(Fenistil) - is closest to second-generation antihistamines; it differs from first-generation drugs in having a significantly less pronounced sedative and muscarinic effect, high antiallergic activity and duration of action.

Thus, first-generation antihistamines, which affect both H1 and other receptors (serotonin, central and peripheral cholinergic receptors, alpha-adrenergic receptors), have various effects, which determined their use in many conditions. But the severity of side effects does not allow them to be considered as the first choice drugs in the treatment of allergic diseases. The experience gained from their use made it possible to develop unidirectional drugs - the second generation of antihistamines.

Second generation antihistamines (non-sedating). Unlike the previous generation, they have almost no sedative and anticholinergic effects, but are distinguished by their selectivity of action on H1 receptors. However, for them varying degrees a cardiotoxic effect was noted.

The most common properties for them are the following.

High specificity and high affinity for H1 receptors with no effect on choline and serotonin receptors.
Rapid onset of clinical effect and duration of action. Prolongation can be achieved due to high protein binding, accumulation of the drug and its metabolites in the body and slow elimination.
Minimal sedative effect when using drugs in therapeutic doses. It is explained by weak passage of the blood-brain barrier due to the structural features of these drugs. Some particularly sensitive individuals may experience mild drowsiness.
Absence of tachyphylaxis with long-term use.
The ability to block potassium channels in the heart muscle, which is associated with prolongation of the QT interval and cardiac arrhythmias. The risk of this side effect increases when antihistamines are combined with antifungals (ketoconazole and intraconazole), macrolides (erythromycin and clarithromycin), antidepressants (fluoxetine, sertraline and paroxetine), when used grapefruit juice, as well as in patients with pronounced violations liver functions.
There are no parenteral forms, but some of them (azelastine, levocabastine, bamipin) are available in forms for topical use.

Below are second generation antihistamines with their most characteristic properties.

Loratadine(Claritin) is one of the most popular second-generation drugs, which is understandable and logical. Its antihistamine activity is higher than that of astemizole and terfenadine, due to greater binding strength to peripheral H1 receptors. The drug has no sedative effect and does not potentiate the effect of alcohol. In addition, loratadine practically does not interact with other medicines and does not have a cardiotoxic effect.

The following antihistamines are classified as drugs local action and are intended to relieve local manifestations of allergies.

Azelastine(Allergodil) is a highly effective treatment allergic rhinitis and conjunctivitis. Used as a nasal spray and eye drops azelastine has virtually no systemic effect.

Cetirizine(Zyrtec) is a highly selective antagonist of peripheral H1 receptors. It is an active metabolite of hydroxyzine, which has a much less pronounced sedative effect. Cetirizine is almost not metabolized in the body, and the rate of its elimination depends on renal function. Its characteristic feature is its high ability to penetrate the skin and, accordingly, its effectiveness in skin manifestations allergies. Cetirizine has not shown any arrhythmogenic effect on the heart either experimentally or clinically.

Conclusions

So, in the doctor’s arsenal there is sufficient quantity antihistamines with various properties. It must be remembered that they provide only symptomatic relief for allergies. In addition, depending on the specific situation, you can use both various drugs, and their diverse forms. It is also important for the doctor to remember the safety of antihistamines.

The disadvantages of most 1st generation antihistamines include the phenomenon of tachyphylaxis (addiction), which requires changing the drug every 7-10 days, although, for example, dimethindene (Fenistil) and clemastine (Tavegil) have been shown to be effective within 20 days without the development of tachyphylaxis ( Kirchhoff C. H. et al., 2003; Koers J. et al., 1999).

The duration of action is from 4-6 hours for diphenhydramine, 6-8 hours for dimethindene, up to 12 (and in some cases 24) hours for clemastine, so the drugs are prescribed 2-3 times a day.

Despite the above disadvantages, 1st generation antihistamines occupy a strong position in allergy practice, especially in pediatrics and geriatrics (Luss L.V., 2009). The availability of injectable forms of these drugs makes them indispensable in acute and emergency situations. The additional anticholinergic effect of chloropyramine significantly reduces itching and skin rashes for atopic dermatitis in children; reduces the volume of nasal secretion and stops sneezing during ARVI. The therapeutic effect of 1st generation antihistamines for sneezing and coughing may be largely due to the blockade of H1 and muscarinic receptors. Cyproheptadine and clemastine, along with their antihistamine effect, have pronounced antiserotonin activity. Dimentiden (Fenistil) additionally inhibits the action of other allergy mediators, in particular kinins. Moreover, the lower cost of 1st generation antihistamines compared to 2nd generation drugs has been established.

The effectiveness of 1st generation oral antihistamines is indicated; their use in combination with oral decongestants in children is not recommended.

Consequently, the advantages of 1st generation antihistamines are: long experience (over 70 years) of use, good study, the possibility of dosed use in children infancy(for dimethindene), indispensable for acute allergic reactions to food products, medications, insect bites, during premedication, in surgical practice.

Features of 2nd generation antihistamine drugs are high affinity (affinity) for H1 receptors, duration of action (up to 24 hours), low permeability through the blood-brain barrier in therapeutic doses, lack of inactivation of the drug by food, and lack of tachyphylaxis. In practice, these drugs are not metabolized in the body. They do not cause sedation, but some patients may experience drowsiness when using them.

The advantages of 2nd generation antihistamines are as follows:

Due to their lipophobicity and poor penetration through the blood-brain barrier, 2nd generation drugs have virtually no sedative effect, although it may be observed in some patients.
The duration of action is up to 24 hours, so most of these drugs are prescribed once a day.
Lack of addiction, which makes it possible to prescribe for a long time (from 3 to 12 months).
After discontinuation of the drug, the therapeutic effect may last for a week.

2nd generation antihistamines are characterized by antiallergic and anti-inflammatory effects. Certain antiallergic effects have been described, but they are clinical significance remains unclear.

Long-term (years) therapy with oral antihistamines, both first and second generation, is safe. Some, but not all, drugs in this group are metabolized in the liver by the cytochrome P450 system and may interact with other drugs. The safety and effectiveness of oral antihistamines in children has been established. They can be prescribed even to small children.

Thus, having such a wide range of antihistamines, the doctor has the opportunity to choose a drug depending on the patient’s age, specific clinical situation, and diagnosis. Antihistamines of the 1st and 2nd generation remain an integral part of the complex treatment of allergic diseases in adults and children.

Literature

Gushchin I. S. Antihistamines. A manual for doctors. M.: Aventis Pharma, 2000, 55 p.
Korovina N. A., Cheburkin A. V., Zakharova I. N., Zaplatnikov A. L., Repina E. A. Antihistamines in practice pediatrician. A guide for doctors. M., 2001, 48 p.
Luss L.V. The choice of antihistamines in the treatment of allergic and pseudoallergic reactions // Ros. allergological journal. 2009, No. 1, p. 1-7.
ARIA // Allergy. 2008. V. 63 (Suppl. 86). P. 88-160
Gillard M., Christophe B., Wels B., Chaterlian P., Peck M., Massingham R. Second generation H1 antagonists potency versus selectivity // Annual Meeting of The European Hisamine Research Society, 2002, May 22, Eger, Hungary.

O. B. Polosyants, Candidate of Medical Sciences

City Clinical Hospital No. 50, Moscow

Today we will talk about:

Antihistamines are substances that suppress the action of free histamine. When an allergen enters the body, histamine is released from mast cells connective tissue, part of the body's immune system. It begins to interact with specific receptors and cause itching, swelling, rash and other allergic manifestations. Antihistamines are responsible for blocking these receptors. There are three generations of these drugs.

1st generation antihistamines

They appeared in 1936 and continue to be used. These drugs bind reversibly to H1 receptors, which explains the need for large dosages and high frequency of administration.

1st generation antihistamines are characterized by the following pharmacological properties:

Reduce muscle tone;
have a sedative, hypnotic and anticholinergic effect;
potentiate the effects of alcohol;
have a local anesthetic effect;
give a quick and strong, but short-term (4-8 hours) therapeutic effect;
long-term use reduces antihistamine activity, so the drugs are changed every 2-3 weeks.

The bulk of 1st generation antihistamines are fat-soluble, can cross the blood-brain barrier and bind to H1 receptors in the brain, which explains the sedative effect of these drugs, which increases after taking alcohol or psychotropic drugs. When taking moderate therapeutic doses in children and high toxic doses in adults, psychomotor agitation may occur. Due to the sedative effect, 1st generation antihistamines are not prescribed to persons whose activities require increased attention.

The anticholinergic properties of these drugs cause atropine-like reactions, such as tachycardia, dryness of the nasopharynx and oral cavity, urinary retention, constipation, and blurred vision. These features may be beneficial for rhinitis, but may increase obstruction respiratory tract caused by bronchial asthma (the viscosity of sputum increases), contribute to the exacerbation of prostate adenoma, glaucoma and other diseases. At the same time, these drugs have an antiemetic and anti-sickness effect, reducing the manifestation of parkinsonism.

A number of these antihistamines are included in combination drugs that are used for migraines, colds, motion sickness, or have a sedative or hypnotic effect.

The extensive list of side effects from taking these antihistamines forces them to be used less frequently in the treatment of allergic diseases. Many developed countries have banned their implementation.

Diphenhydramine

Diphenhydramine is prescribed for hay fever, urticaria, seasickness, air sickness, vasomotor runny nose, bronchial asthma, allergic reactions caused by the introduction medicinal substances(for example, antibiotics), in the treatment of peptic ulcers, dermatoses, etc.

Advantages: high antihistamine activity, reduced severity of allergic, pseudo-allergic reactions. Diphenhydramine has an antiemetic and antitussive effect, has a local anesthetic effect, making it an alternative to Novocaine and Lidocaine if they are intolerant.

Cons: unpredictability of the consequences of taking the drug, its effect on the central nervous system. It can cause urinary retention and dry mucous membranes. Side effects include sedative and hypnotic effects.

Diazolin

Diazolin has the same indications for use as other antihistamines, but differs from them in the characteristics of their effects.

Advantages: a weakly expressed sedative effect allows it to be used where it is undesirable to have a depressant effect on the central nervous system.

Cons: irritates the mucous membranes of the gastrointestinal tract, causes dizziness, difficulty urinating, drowsiness, slows down mental and motor reactions. There is information about the toxic effect of the drug on nerve cells.

Suprastin

Suprastin is prescribed for the treatment of seasonal and chronic allergic conjunctivitis, urticaria, atopic dermatitis, Quincke's edema, itching of various etiologies, and eczema. It is used in parenteral form for acute allergic conditions requiring emergency care.

Advantages: does not accumulate in blood serum, therefore, even with prolonged use does not cause an overdose. Due to its high antihistamine activity, a rapid therapeutic effect is observed.

Cons: side effects - drowsiness, dizziness, inhibition of reactions, etc. - are present, although less pronounced. The therapeutic effect is short-term, in order to prolong it, Suprastin is combined with H1-blockers that do not have sedative properties.

Tavegil

Tavegil in the form of injections is used for angioedema, as well as anaphylactic shock, as a preventive and therapeutic agent for allergic and pseudoallergic reactions.

Advantages: has a longer and stronger effect antihistamine effect than Diphenhydramine, and has a more moderate sedative effect.

Cons: may itself cause an allergic reaction, has some inhibitory effects.

Fenkarol

Fenkarol is prescribed when addiction to other antihistamines occurs.

Advantages: has mild sedative properties, does not have a pronounced inhibitory effect on the central nervous system, is low-toxic, blocks H1 receptors, and is able to reduce the content of histamine in tissues.

Cons: less antihistamine activity compared to Diphenhydramine. Fenkarol is used with caution in the presence of diseases of the gastrointestinal tract, cardiovascular system and liver.

Antihistamines 2nd generation

They have advantages compared to first generation drugs:

There is no sedative and anticholinergic effect, since these drugs do not cross the blood-brain barrier, only some individuals experience moderate drowsiness;
mental activity, physical activity do not suffer;
the effect of the drugs reaches 24 hours, so they are taken once a day;
they are not addictive, which allows them to be prescribed for a long time (3-12 months);
when you stop taking the drugs, the therapeutic effect lasts about a week;
drugs are not adsorbed from food in the gastrointestinal tract.

But 2nd generation antihistamines have a cardiotoxic effect varying degrees Therefore, when taking them, cardiac activity is monitored. They are contraindicated in elderly patients and patients suffering from disorders of the cardiovascular system.

The occurrence of cardiotoxic effects is explained by the ability of 2nd generation antihistamines to block potassium channels of the heart. The risk increases when these drugs are combined with antifungal drugs, macrolides, antidepressants, from drinking grapefruit juice, and if the patient has severe liver dysfunction.

Claridol

Claridol is used to treat seasonal and cyclical allergic rhinitis, urticaria, allergic conjunctivitis, Quincke's edema and a number of other diseases of allergic origin. It copes with pseudoallergic syndromes and allergies to insect bites. Included in comprehensive measures for the treatment of itchy dermatoses.

Advantages: Claridol has antipruritic, antiallergic, antiexudative effects. The drug reduces capillary permeability, prevents the development of edema, and relieves spasm of smooth muscles. It has no effect on the central nervous system and does not have an anticholinergic or sedative effect.

Cons: Occasionally, after taking Claridol, patients complain of dry mouth, nausea and vomiting.

Clarisens

Clarisens is able to suppress the release of histamine and leukotriene C4 from mast cells. It is used for the treatment and prevention of allergy manifestations such as rhinitis, conjunctivitis, and dermatosis. The drug enters complex treatment Quincke's edema and various allergic insect bites. In the presence of pseudo-allergic reactions, Clarisens is able to quickly alleviate the patient's condition.

Advantages: the drug is not addictive, does not affect the functioning of the central nervous system, has an anti-exudative effect, relieves swelling and spasms smooth muscle. The therapeutic effect occurs within half an hour after taking the medicine and lasts for a day.

Cons: a side effect occurs when the patient has an individual intolerance to the drug and is expressed by dyspepsia, severe headache, fatigue, and allergic reactions.

Clarotadine

Clarotadine contains active substance loratadine, which is a selective H1-blocker histamine receptors, on which it has a direct impact, allowing you to avoid unwanted effects inherent in other antihistamines. Indications for use are allergic conjunctivitis, acute chronic and idiopathic urticaria, rhinitis, pseudoallergic reactions associated with the release of histamine, allergic insect bites, itchy dermatoses.

Advantages: the drug does not have a sedative effect, is not addictive, acts quickly and for a long time.

Cons: undesirable consequences of taking Clarodin include disorders nervous system: asthenia, anxiety, drowsiness, depression, amnesia, tremor, agitation in a child. Dermatitis may appear on the skin. Frequent and painful urination, constipation and diarrhea. Weight gain due to disruption of the endocrine system. Damage to the respiratory system can be manifested by cough, bronchospasm, sinusitis and similar manifestations.

Lomilan

Lomilan is indicated for seasonal and permanent allergic rhinitis, skin rashes of allergic origin, pseudo-allergies, reactions to insect bites, allergic inflammation mucous membrane of the eyeball.

Advantages: Lomilan is able to relieve itching, reduce the tone of smooth muscles and the production of exudate (a special fluid that appears during the inflammatory process), and prevent tissue swelling within half an hour from the moment of taking the drug. The greatest effectiveness occurs after 8-12 hours, then subsides. Lomilan is not addictive and does not have any negative impact on the activity of the nervous system.

Cons: adverse reactions occur rarely, manifested by headache, feeling of fatigue and drowsiness, inflammation of the gastric mucosa, nausea.

LauraHexal

LauraHexal is recommended for year-round and seasonal allergic rhinitis, conjunctivitis, itchy dermatoses, urticaria, Quincke's edema, allergic insect bites and various pseudo-allergic reactions.

Advantages: the drug has neither anticholinergic nor central action, its use does not affect the attention, psychomotor functions, performance and mental qualities of the patient.

Minis: LauraHexal is usually well tolerated, but occasionally it causes increased fatigue, dry mouth, headache, tachycardia, dizziness, allergic reactions, cough, vomiting, gastritis, liver dysfunction.

Claritin

Claritin contains active ingredient– loratadine, which blocks H1-histamine receptors and prevents the release of histamine, bradycanin and serotonin. Antihistamine effectiveness lasts a day, and therapeutic effectiveness occurs after 8-12 hours. Claritin is prescribed for the treatment of rhinitis of allergic etiology, allergic skin reactions, food allergies And mild degree bronchial asthma.

Advantages: highly effective in the treatment of allergic diseases, the drug does not cause addiction or drowsiness.

Cons: cases of side effects are rare, they are manifested by nausea, headache, gastritis, agitation, allergic reactions, drowsiness.

Rupafin

Rupafin has a unique active component– rupatadine, characterized by antihistamine activity and a selective effect on H1-histamine peripheral receptors. It is prescribed for chronic idiopathic urticaria and allergic rhinitis.

Advantages: Rupafin effectively copes with the symptoms of the allergic diseases listed above and does not affect the functioning of the central nervous system.

Cons: undesirable consequences taking the drug - asthenia, dizziness, fatigue, headache, drowsiness, dry mouth. It can affect the respiratory, nervous, musculoskeletal and digestive systems, as well as metabolism and skin.

Kestin

Kestin blocks histamine receptors, which increase vascular permeability, causing muscle spasms, leading to an allergic reaction. Used to treat allergic conjunctivitis, rhinitis and chronic idiopathic urticaria.

Advantages: the drug acts within an hour after application, the therapeutic effect lasts for 2 days. A five-day intake of Kestin allows you to maintain the antihistamine effect for about 6 days. Sedative effects are practically non-existent.

Cons: the use of Kestin can cause insomnia, abdominal pain, nausea, drowsiness, asthenia, headache, sinusitis, dry mouth.

New, 3rd generation antihistamines

These substances are prodrugs, which means that when they enter the body, they are converted from their original form into pharmacologically active metabolites.

All 3rd generation antihistamines do not have cardiotoxic or sedative effects, so they can be used by persons whose activities are related to high concentration attention.

These drugs block H1 receptors and also have additional influence for allergic manifestations. They are highly selective, do not cross the blood-brain barrier, and therefore are not characterized by negative consequences from the central nervous system, absent side effect on the heart.

The presence of additional effects promotes the use of 3rd generation antihistamines for long-term treatment most allergic manifestations.

Gismanal

Gismanal is prescribed as a therapeutic and prophylactic agent for hay fever, allergic skin reactions, including urticaria, allergic rhinitis. The effect of the drug develops over 24 hours and reaches its maximum after 9-12 days. Its duration depends on previous therapy.

Advantages: the drug has virtually no sedative effect and does not enhance the effect of taking sleeping pills or alcohol. It also does not affect driving ability or mental performance.

Cons: Gismanal can cause increased appetite, dry mucous membranes, tachycardia, drowsiness, arrhythmia, prolongation of the QT interval, palpitations, collapse.

Trexil

Trexyl is a fast-acting, selectively active H1 receptor antagonist, a derivative of buterophenol, which differs in chemical structure from its analogues. Used for allergic rhinitis to relieve its symptoms, allergic dermatological manifestations (dermatographism, contact dermatitis, urticaria, atonic eczema), asthma, atonic and provoked physical activity, as well as in connection with acute allergic reactions to various irritants.

Advantages: absence of sedative and anticholinergic effect, influence on psychomotor activity and well-being of a person. The drug is safe to use by patients with glaucoma and those suffering from prostate disorders.

Telfast

Telfast is a highly effective antihistamine, which is a metabolite of terfenadine, and therefore has great similarity with histamine H1 receptors. Telfast contacts them and blocks them, preventing their biological manifestations as allergic symptoms. The membranes of mast cells are stabilized and the release of histamine from them is reduced. Indications for use include angioedema, urticaria, and hay fever.

Advantages: does not exhibit sedative properties, does not affect the speed of reactions and concentration, heart function, is not addictive, highly effective against the symptoms and causes of allergic diseases.

Cons: rare consequences of taking the drug are headache, nausea, dizziness, there are rare reports of shortness of breath, anaphylactic reaction, skin flushing.

Zyrtec

Zyrtec is a competitive antagonist of the hydroxyzine metabolite, histamine. The drug facilitates the course and sometimes prevents the development of allergic reactions. Zirtec limits the release of mediators, reduces the migration of eosinophils, basophils, and neutrophils. The drug is used for allergic rhinitis, bronchial asthma, urticaria, conjunctivitis, dermatitis, fever, itching, antineurotic edema.

Advantages: effectively prevents the occurrence of edema, reduces capillary permeability, and relieves spasm of smooth muscles. Zyrtec does not have anticholinergic or antiserotonin effects.

Cons: Improper use of the drug can lead to dizziness, migraines, drowsiness, and allergic reactions.

Antihistamines for children

To treat allergic manifestations in children, antihistamines of all three generations are used.

1st generation antihistamines are distinguished by the fact that they quickly manifest their effect medicinal property and are excreted from the body. They are in demand for treatment acute manifestations allergic reactions. They are prescribed in short courses. The most effective of this group are Tavegil, Suprastin, Diazolin, Fenkarol.

A significant percentage of side effects leads to a decrease in the use of these medications for childhood allergies.

2nd generation antihistamines do not cause a sedative effect, act for a longer time and are usually used once a day. Few side effects. Among the drugs in this group, Ketitofen, Fenistil, Cetrin, Erius are used to treat manifestations of childhood allergies.

The 3rd generation of antihistamines for children includes Gismanal, Terfen and others. They are used for chronic allergic processes because they are capable of for a long time be in the body. There are no side effects.

Negative consequences:

1st generation: headache, constipation, tachycardia, drowsiness, dry mouth, blurred vision, urinary retention and lack of appetite;
2nd generation: negative effect on the heart and liver;
3rd generation: none, recommended for use from 3 years of age.

Antihistamines are produced for children in the form of ointments (allergic skin reactions), drops, syrups and tablets for oral administration.

Antihistamines during pregnancy

In the first trimester of pregnancy, it is forbidden to take antihistamines. In the second, they are prescribed only in extreme cases, since none of these medicinal products is not completely safe.

Natural antihistamines, which include vitamins C, B12, pantothenic, oleic and nicotinic acid, zinc, fish oil.

The safest antihistamines are Claritin, Zyrtec, Telfast, Avil, but their use must be agreed with a doctor.

Allergic reactions are divided into immediate, developing immediately after exposure to the antigen, and delayed, appearing after several days or even weeks. For immediate allergies, antihistamines are most effective. The principle of their action is based on blocking free histamine, which is released in the body in response to a physical or chemical irritant. Having a structure similar to a biogenic amine, the active substance blocks histamine receptors, preventing the amine itself from performing the functions of a mediator of allergic reactions.

There are three generations of antihistamines. Developed at different times, they differ in their selectivity of action. Each of the subsequent pharmaceutical lines is more selective, that is, the active substance of the drug binds predominantly to one type of receptor. This increases the safety of the drug and reduces the risk of side effects.

The first generation was created in 1936, its representatives are Diphenhydramine, Diazolin, Tavegil, Suprastin, Fenkarol. They show good results as histamine blockers: they eliminate allergic manifestations in the form of rashes, swelling, itching. However, all these drugs have a short-term effect (3-4 hours), and with long-term use they reduce their activity, and also give quite a lot of side effects:

due to low selectivity, they have an undesirable effect on cellular structures many organs, and therefore contraindicated for peptic ulcers, renal, hepatic and cardiovascular pathologies, glaucoma, epilepsy;
being anticholinergics, they can cause dysfunction of the central nervous system, headache, dizziness, drop in blood pressure;
reduce muscle tone;
have a hypnotic effect;
cause an increase in body weight.

Important information!

Due to the pronounced sedative effect of first-generation antihistamines, if used, driving or performing other work that requires increased attention or quick reaction is only possible 12 hours after taking the medication.

Second generation drugs - Hexal, Clarisens, Kestin, Claritin, Clarotadine, Lomilan, Zirtec, Rupafin and others - appeared in the 80s of the last century. They act more selectively, affecting mainly histamine receptors, and therefore have fewer side effects.

Another advantage is the lack of addiction and the duration of action is up to 24 hours. This allows you to take the medicine once a day and not increase the dose during long-term use. However, due to the cardiotoxic effect, most of these drugs require constant monitoring cardiac activity, and for patients with serious cardiovascular pathologies, 2nd generation antihistamines are contraindicated.

IN recent years To treat all types of allergies, drugs are successfully used whose active ingredients belong to the category of prodrugs, that is, they are converted into pharmacologically active compounds already in the body, as a result metabolic processes. The effectiveness of these products is several times higher than that of their predecessors. They also have high selectivity, and therefore do not produce either sedative or cardiotoxic effects, and, therefore, are the safest.

The list of new generation antihistamines is still relatively small, but they all have a common advantage: they can be taken for diseases of the heart, gastrointestinal tract, kidney and liver pathologies, as well as for people whose work requires a high concentration of attention. Some of the drugs in this group are not contraindicated during pregnancy and childhood.

Comparative characteristics of 3rd generation drugs

Indications for the use of this category of drugs are:

food allergies;
seasonal and chronic allergic conjunctivitis and rhinitis;
hives;
exudative diathesis;
contact and atopic dermatitis.

Drugs with the same active ingredient can be produced under different names trademarks(these are so-called synonymous drugs).

Allegra

It is also produced under the names Fexadin, Fexofenadine, Telfast, Fexofast, Tigofast. The active ingredient is fexofenadine hydrochloride. Release form: film-coated tablets of 120 and 180 mg.

The initial effect is produced an hour after administration, the maximum concentration in the blood is reached after 3 hours, the half-life is about 12 hours, the duration of action is a day. A single dose is 180 mg, the course of treatment is determined individually. Since clinical trials the effect of fexofenadine on the fetus and children's body have not been carried out, during pregnancy, children under 12 years of age and breastfeeding women, it is prescribed only in cases of special need.

The cost of a drug depends on the content of the main substance and the manufacturer. For example, 10 tablets of 120 mg of Fexadine Ranbaxy (India) cost 220 rubles, the same package of Allegra from Sanofi-Aventis (France) costs 550 rubles, and 10 tablets of 180 mg of Telfast Sanofi-Aventis cost 530 rubles.

Cetirizine

Other trade names: Cetrin, Cetrinal, Parlazin, Zodak, Amertil, Allertek, Zirtec. A substance that is active against histamine is cetirizine dihydrochloride. Available in tablets containing 10 mg of active substance, as well as in the form of drops, solutions and syrup.

The initial effect is observed 1 – 1.5 hours after administration, the total duration of action is up to a day, metabolites are excreted within 10-15 hours in the urine. Single (and daily) dose of 10 mg. The drug is not addictive and can be used for long-term therapy. It is not recommended for children under 1 year of age and pregnant women to take it.

Approximate cost of cetirizine and its analogues:

Cetirizine, manufacturer Vertex, Russia (10 tablets) – 66 rubles;
Tsetrin, manufacturer Dr. Reddy, India (20 tables) – 160 rubles;
Zodak, manufacturer Zentiva, Czech Republic (10 tablets) – 140 rubles;
Zirtek, manufacturer USB Farshim, Belgium (drops in 10 ml bottles) – 320 rubles.

Xizal

Synonyms: Suprastinex, Levocetirizine, Glencet, Zilola, Alerzin. Active ingredient: Levocetirizine dihydrochloride. The medicine is available in 5 mg tablets and drops; the dosage form for children is syrup.

The affinity for histamine receptors of this drug is several times higher than that of other representatives of this series, so its effect lasts for 2 days. Metabolic products are excreted by the kidneys, the half-life is 8 – 10 hours. The daily dose for adults and children over 6 years of age is 5 mg. Contraindications to the use of levocetirizine are congenital disorders carbohydrate metabolism.

Estimated cost of drugs:

Xyzal, manufacturer YUSB Farshim, Belgium (drops in 10 ml bottles) – 440 rubles;
Levocetirizine, manufacturer Teva, France (10 tablets) – 270 rubles;
Alerzin, manufacturer Eric, Hungary (14 tables) –300 rubles;
Suprastinex, manufacturer Eric, Hungary (7 tables) – 150 rubles.

Desloratadine

Other trade names: Erius, Dezal, Allergostop, Fribris, Alersis, Lordestin. The bioactive substance is desloratadine. Release forms: film-coated tablets of 5 mg, solution containing the active substance 5 mg/ml and syrup.

The maximum concentration in the blood is observed after 3–4 hours, the half-life is 20–30 hours, the total duration of action is 24 hours. A single dose for adults and children over 12 years of age is 5 mg; the dosage for children from 2 to 12 years of age is determined individually. For pregnant and lactating women, the drug is prescribed for life-threatening conditions.

Cost of desloratadine and its synonyms:

Desloratadine, manufacturer Vertex, Russia (10 tablets) – 145 rubles;
Lordestin, Bayer, USA, manufacturer Gedeon Richter, Hungary (10 tablets) – 340 rubles;
Erius, manufacturer Bayer, USA (7 tablets) – 90 rubles.

All antiallergic drugs are prescribed by a doctor, taking into account the specifics of their action, the causes of allergies, the age and characteristics of the patient’s body. When taking antihistamines, you should strictly adhere to the rules specified in the instructions.

Histamine, this most important mediator of various physiological and pathological processes in the body, was chemically synthesized in 1907. Subsequently, it was isolated from animal and human tissues (Windaus A., Vogt W.). Even later, its functions were determined: gastric secretion, neurotransmitter function in the central nervous system, allergic reactions, inflammation, etc. Almost 20 years later, in 1936, the first substances with antihistamine activity were created (Bovet D., Staub A.). And already in the 60s, the heterogeneity of histamine receptors in the body was proven and three of their subtypes were identified: H1, H2 and H3, differing in structure, localization and physiological effects that occur during their activation and blockade. From this time on, an active period of synthesis and clinical testing of various antihistamines began.

Most of the antihistamines used have a number of specific pharmacological properties that characterize them as a separate group. These include the following effects: antipruritic, decongestant, antispastic, anticholinergic, antiserotonin, sedative and local anesthetic, as well as prevention of histamine-induced bronchospasm. Some of them are caused not by histamine blockade, but by structural features.

Antihistamines block the effect of histamine on H1 receptors through the mechanism of competitive inhibition, and their affinity for these receptors is much lower than that of histamine. Therefore, these drugs are not able to displace the histamine bound to the receptor; they only block unoccupied or released receptors. Accordingly, H1 blockers are most effective in preventing immediate allergic reactions, and in the event of a developed reaction, they prevent the release of new portions of histamine.

According to their chemical structure, most of them belong to fat-soluble amines, which have a similar structure. The core (R1) is represented by an aromatic and/or heterocyclic group and is linked via a nitrogen, oxygen or carbon molecule (X) to the amino group. The core determines the severity of antihistamine activity and some of the properties of the substance. Knowing its composition can predict the strength of the drug and its effects, such as its ability to penetrate the blood-brain barrier.

There are several classifications of antihistamines, although none of them is generally accepted. According to one of the most popular classifications, antihistamines, based on the time of creation, are divided into first and second generation drugs. First generation drugs are also commonly called sedatives (based on the dominant side effect) in contrast to non-sedating second generation drugs. Currently, it is customary to distinguish the third generation: it includes fundamentally new drugs - active metabolites, which, in addition to the highest antihistamine activity, exhibit the absence of a sedative effect and the cardiotoxic effect characteristic of second-generation drugs (see).

First generation antihistamines (sedatives). All of them are highly soluble in fats and, in addition to H1-histamine, also block cholinergic, muscarinic and serotonin receptors. As competitive blockers, they reversibly bind to H1 receptors, which necessitates the use of fairly high doses. The following pharmacological properties are most characteristic of them.

The sedative effect is determined by the fact that most first-generation antihistamines, easily soluble in lipids, penetrate well through the blood-brain barrier and bind to H1 receptors in the brain. Perhaps their sedative effect consists of blocking central serotonin and acetylcholine receptors. The degree of manifestation of the first generation sedative effect varies between drugs and in different patients from moderate to severe and increases when combined with alcohol and psychotropic drugs. Some of them are used as sleeping pills (doxylamine). Rarely, instead of sedation, psychomotor agitation occurs (more often in moderate therapeutic doses in children and in high toxic doses in adults). Because of the sedative effect, most medications should not be used while performing tasks that require alertness. All first-generation drugs potentiate the effect of sedatives and hypnotics, narcotic and non-narcotic analgesics, monoamine oxidase inhibitors and alcohol.
The anxiolytic effect characteristic of hydroxyzine may be due to suppression of activity in certain areas of the subcortical region of the central nervous system.
Atropine-like reactions associated with the anticholinergic properties of drugs are most typical for ethanolamines and ethylenediamines. Manifested by dry mouth and nasopharynx, urinary retention, constipation, tachycardia and visual impairment. These properties ensure the effectiveness of the drugs under discussion for non-allergic rhinitis. At the same time, they can increase obstruction in bronchial asthma (due to an increase in sputum viscosity), cause exacerbation of glaucoma and lead to bladder outlet obstruction in prostate adenoma, etc.
The antiemetic and anti-motion sickness effect is also likely associated with the central anticholinergic effect of the drugs. Some antihistamines (diphenhydramine, promethazine, cyclizine, meclizine) reduce the stimulation of vestibular receptors and inhibit the function of the labyrinth, and therefore can be used for movement disorders.
A number of H1-histamine blockers reduce the symptoms of parkinsonism, which is due to the central inhibition of the effects of acetylcholine.
The antitussive effect is most characteristic of diphenhydramine; it is realized through a direct effect on the cough center in the medulla oblongata.
The antiserotonin effect, primarily characteristic of cyproheptadine, determines its use for migraine.
The α1-blocking effect with peripheral vasodilation, especially inherent in phenothiazine antihistamines, may lead to a transient decrease in blood pressure in sensitive individuals.
A local anesthetic (cocaine-like) effect is characteristic of most antihistamines (occurs due to a decrease in membrane permeability to sodium ions). Diphenhydramine and promethazine are stronger local anesthetics than novocaine. At the same time, they have systemic quinidine-like effects, manifested by prolongation of the refractory phase and the development of ventricular tachycardia.
Tachyphylaxis: a decrease in antihistamine activity with long-term use, confirming the need to alternate medications every 2-3 weeks.
It should be noted that first-generation antihistamines differ from the second generation in their short duration of action with a relatively rapid onset of clinical effect. Many of them are available in parenteral forms. All of the above, as well as low cost, determine the widespread use of antihistamines today.

The most commonly used are chloropyramine, diphenhydramine, clemastine, cyproheptadine, promethazine, fenkarol and hydroxyzine.

Chloropyramine(suprastin) is one of the most widely used sedative antihistamines. It has significant antihistamine activity, peripheral anticholinergic and moderate antispasmodic effects. Effective in most cases for the treatment of seasonal and year-round allergic rhinoconjunctivitis, Quincke's edema, urticaria, atopic dermatitis, eczema, itching of various etiologies; in parenteral form - for the treatment of acute allergic conditions requiring emergency care. Provides a wide range of therapeutic doses used. It does not accumulate in the blood serum, therefore it does not cause an overdose with long-term use. Suprastin is characterized by a rapid onset of effect and short duration (including side effects). In this case, chloropyramine can be combined with non-sedating H1-blockers in order to increase the duration of the antiallergic effect. Suprastin is currently one of the best-selling antihistamines in Russia. This is objectively due to the proven high efficiency, controllability of its clinical effect, the availability of various dosage forms, including injectable ones, and low cost.

Diphenhydramine, best known in our country under the name diphenhydramine, is one of the first synthesized H1 blockers. It has fairly high antihistamine activity and reduces the severity of allergic and pseudo-allergic reactions. Due to its significant anticholinergic effect, it has an antitussive, antiemetic effect and at the same time causes dryness of the mucous membranes and urinary retention. Due to its lipophilicity, diphenhydramine produces pronounced sedation and can be used as a hypnotic. It has a significant local anesthetic effect, as a result of which it is sometimes used as an alternative in cases of intolerance to novocaine and lidocaine. Diphenhydramine is available in various dosage forms, including for parenteral use, which has determined its widespread use in emergency therapy. However, a significant range of side effects, unpredictability of consequences and effects on the central nervous system require increased attention when using it and, if possible, the use of alternative means.

Clemastine(tavegil) is a highly effective antihistamine, similar in action to diphenhydramine. It has high anticholinergic activity, but penetrates the blood-brain barrier to a lesser extent. It also exists in injection form, which can be used as an additional remedy for anaphylactic shock and angioedema, for the prevention and treatment of allergic and pseudoallergic reactions. However, hypersensitivity to clemastine and other antihistamines with a similar chemical structure is known.

Cyproheptadine(peritol), along with an antihistamine, has a significant antiserotonin effect. In this regard, it is mainly used for some forms of migraine, dumping syndrome, as an appetite enhancer, and for anorexia. of various origins. It is the drug of choice for cold urticaria.

Promethazine(pipolfen) - a pronounced effect on the central nervous system determined its use in Meniere's syndrome, chorea, encephalitis, sea and air sickness, as an antiemetic. In anesthesiology, promethazine is used as a component lytic mixtures to potentiate anesthesia.

Quifenadine(fenkarol) - has less antihistamine activity than diphenhydramine, but is also characterized by less penetration through the blood-brain barrier, which determines the lower severity of its sedative properties. In addition, fenkarol not only blocks histamine H1 receptors, but also reduces the content of histamine in tissues. May be used in cases of developing tolerance to other sedating antihistamines.

Hydroxyzine(atarax) - despite the existing antihistamine activity, it is not used as an antiallergic agent. It is used as an anxiolytic, sedative, muscle relaxant and antipruritic agent.

Thus, first-generation antihistamines, which affect both H1 and other receptors (serotonin, central and peripheral cholinergic receptors, α-adrenergic receptors), have different effects, which has determined their use in a variety of conditions. But the severity of side effects does not allow them to be considered as the first choice drugs in the treatment of allergic diseases. The experience gained from their use made it possible to develop unidirectional drugs - the second generation of antihistamines.

Second generation antihistamines (non-sedating). Unlike the previous generation, they have almost no sedative and anticholinergic effects, but are distinguished by their selectivity of action on H1 receptors. However, they exhibit a cardiotoxic effect to varying degrees.

The most common properties for them are the following.

High specificity and high affinity for H1 receptors with no effect on choline and serotonin receptors.
Rapid onset of clinical effect and duration of action. Prolongation can be achieved due to high protein binding, accumulation of the drug and its metabolites in the body and slow elimination.
Minimal sedative effect when using drugs in therapeutic doses. It is explained by weak passage of the blood-brain barrier due to the structural features of these drugs. Some particularly sensitive individuals may experience moderate drowsiness, which is rarely a reason to discontinue the drug.
Absence of tachyphylaxis with long-term use.
The ability to block potassium channels in the heart muscle, which is associated with prolongation of the QT interval and cardiac arrhythmias. The risk of this side effect increases when antihistamines are combined with antifungals (ketoconazole and intraconazole), macrolides (erythromycin and clarithromycin), antidepressants (fluoxetine, sertraline and paroxetine), when drinking grapefruit juice, as well as in patients with severe liver dysfunction.
There are no parenteral forms, but some of them (azelastine, levocabastine, bamipin) are available in forms for topical use.

Below are second generation antihistamines with their most characteristic properties.

Terfenadine- the first antihistamine without an inhibitory effect on the central nervous system. Its creation in 1977 was the result of a study of both the types of histamine receptors and the features of the structure and action of existing H1 blockers, and marked the beginning of the development of a new generation of antihistamines. Currently, terfenadine is used less and less, which is associated with an increased ability to cause fatal arrhythmias associated with prolongation of the QT interval (torsade de pointes).

Astemizole- one of the longest active drugs group (the half-life of its active metabolite is up to 20 days). It is characterized by irreversible binding to H1 receptors. It has virtually no sedative effect and does not interact with alcohol. Since astemizole has a delayed effect on the course of the disease, when acute process its use is inappropriate, but may be justified in chronic allergic diseases. Since the drug has the ability to accumulate in the body, the risk of developing serious violations heart rhythm, sometimes fatal. Due to these dangerous side effects, the sale of astemizole in the United States and some other countries has been suspended.

Akrivastine(Semprex) is a drug with high antihistamine activity with minimally expressed sedative and anticholinergic effects. A feature of its pharmacokinetics is its low level of metabolism and lack of accumulation. Acrivastine is preferable in cases where there is no need for constant antiallergic treatment due to the rapid achievement of effect and short-term action, which allows the use of a flexible dosing regimen.

Dimetenden(fenistil) - is closest to first-generation antihistamines, but differs from them by a significantly less pronounced sedative and muscarinic effect, higher antiallergic activity and duration of action.

Loratadine(Claritin) is one of the most widely purchased second-generation drugs, which is understandable and logical. Its antihistamine activity is higher than that of astemizole and terfenadine, due to greater binding strength to peripheral H1 receptors. The drug has no sedative effect and does not potentiate the effect of alcohol. In addition, loratadine practically does not interact with other drugs and does not have a cardiotoxic effect.

The following antihistamines are topical drugs and are intended to relieve local manifestations of allergies.

Levocabastine(histimet) is used as eye drops to treat histamine-dependent allergic conjunctivitis or as a spray for allergic rhinitis. At local application enters the systemic circulation in small quantities and does not have undesirable effects on the central nervous and cardiovascular systems.

Azelastine(allergodil) is a highly effective remedy for the treatment of allergic rhinitis and conjunctivitis. Used as a nasal spray and eye drops, azelastine has virtually no systemic effects.

Other topical antihistamine— bamipin (Soventol) in the form of a gel is intended for use for allergic skin lesions accompanied by itching, insect bites, jellyfish burns, frostbite, sunburn, as well as mild thermal burns.

Third generation antihistamines (metabolites). Their fundamental difference is that they are active metabolites of previous generation antihistamines. Their main feature is the inability to influence the QT interval. Currently there are two drugs available: cetirizine and fexofenadine.

Cetirizine(Zyrtec) is a highly selective antagonist of peripheral H1 receptors. It is an active metabolite of hydroxyzine, which has a much less pronounced sedative effect. Cetirizine is almost not metabolized in the body, and the rate of its elimination depends on renal function. Its characteristic feature is its high ability to penetrate the skin and, accordingly, its effectiveness in treating skin manifestations of allergies. Cetirizine, neither experimentally nor in the clinic, showed any arrhythmogenic effect on the heart, which predetermined the area practical use metabolite drugs and determined the creation of a new drug - fexofenadine.

Fexofenadine(Telfast) is an active metabolite of terfenadine. Fexofenadine does not undergo transformations in the body and its kinetics does not change with impaired liver and kidney function. He does not enter into any drug interactions, does not have a sedative effect and does not affect psychomotor activity. In this regard, the drug is approved for use by persons whose activities require increased attention. A study of the effect of fexofenadine on the QT value showed both in experiment and in the clinic complete absence cardiotropic effect when using high doses and long-term use. Along with maximum safety, this drug demonstrates the ability to relieve symptoms in the treatment of seasonal allergic rhinitis and chronic idiopathic urticaria. Thus, the pharmacokinetic features, safety profile and high clinical effectiveness make fexofenadine the most promising of the antihistamines at present.

So, in the doctor’s arsenal there is a sufficient number of antihistamines with various properties. It must be remembered that they provide only symptomatic relief for allergies. In addition, depending on the specific situation, you can use both different drugs and their varied forms. It is also important for the doctor to remember the safety of antihistamines.

Three generations of antihistamines (trade names in parentheses)

I generation	II generation	III generation
Diphenhydramine (diphenhydramine, benadryl, allergin) Clemastine (tavegil) Doxylamine (Decaprin, Donormil) Diphenylpyralin Bromodiphenhydramine Dimenhydrinate (daedalone, dramamine) Chloropyramine (suprastin) Pyrilamine Antazoline Mepyramin Brompheniramine Chloropheniramine Dexchlorpheniramine Pheniramine (Avil) Mebhydrolin (diazolin) Quifenadine (fenkarol) Sequifenadine (bicarfen) Promethazine (phenergan, diprazine, pipolphen) Trimeprazine (teralen) Oxomemazine Alimemazine Cyclizine Hydroxyzine (atarax) Meclizine (Bonine) Cyproheptadine (peritol)	Acrivastine (Semprex) Astemizole (gismanal) Dimetindene (fenistil) Oxatomide (tinset) Terfenadine (bronal, histadine) Azelastine (allergodil) Levocabastine (histimet) Mizolastine Loratadine (Claritin) Epinastine (alesion) Ebastine (kestin) Bamipin (Soventol)	Cetirizine (Zyrtec) Fexofenadine (Telfast)

Every person experiences an allergic reaction from time to time, and some people suffer from allergies almost all the time, so new generation drugs are relevant for most people. Statistics show that the number of allergy sufferers is steadily increasing every year. This is due to the environmental situation and weakening.

Antihistamines - what are they in simple words?

Medicines help fight allergies. They are medications that weaken the effects of histamine in the human body. Histamine is a special substance produced by cells immune system body and designed to fight bacteria and viruses. But since an allergy is a “mistake” of the immune system, histamine does not bring any benefit, but acts on the receptors, causing swelling of the mucous membranes, redness and itching of the skin, etc. Antihistamines act on H1-histamine receptors and block them. Thus, histamine cannot influence the receptors, as a result of which the manifestations of allergies are reduced: itching, tearing, swelling of the mucous membranes, etc. are reduced.

There are several generations of antihistamines, each of which has its own differences. The first generation was created in the 30s of the last century and became a real breakthrough in the fight against allergies. After some time, second and third generation drugs were created.

Generations of antihistamines differ significantly from each other: they have different properties and side effects. This applies to drugs of three generations. 4th generation antihistamines are very conventional; most often this is an advertising ploy by manufacturers who want to emphasize the innovativeness of their products. Which ones are better? Let's take a look at the features of each category to choose the best antihistamines.

1st generation antihistamines

This is the most common group of anti-allergy drugs that have a pronounced sedative effect: they cause drowsiness and calm. They are quite powerful and do not last long, usually 4-5 hours, can be found in any pharmacy, their price is quite low, and their quality and effectiveness are time-tested. The use of first-generation antihistamines lasts no more than 7-10 days, after this period addiction begins and the effectiveness of the drugs noticeably decreases. These drugs are prescribed after some vaccines, during treatment skin diseases, as well as in case of acute allergic reaction to a temporary external irritant.

TO side effects This group includes:

decline ;
increased appetite;
rapid heartbeat;
discomfort in the stomach, vomiting and nausea;
thirst, drying of mucous membranes;
weakening of attention and muscle tone.

Suprastin. Available in ampoules and tablets, the active substance is chloropyramine. Used to treat edema, eczema, urticaria, allergic rhinitis, swelling of the mucous membranes. Also used to eliminate skin itching, incl. after an insect bite. Suprastin can be given to children starting from one month, but it is important to calculate the dosage. This remedy can be used for high temperature, which is difficult to knock down, and also as a sedative for colds and viral diseases.

Suprastin should not be used during pregnancy and lactation.

Diazolin. That's enough mild remedy, which does not cause drowsiness and is suitable for long-term use. Diazolin can be used during pregnancy, with the exception of the first trimester, and is also suitable for children from two years of age. This product is available in the form of tablets, ampoules, and suspensions with various dosages.
Fenistil. Very effective universal remedy, which is used for all types of allergies. Causes drowsiness only in the first few days of treatment, then the sedative effect disappears. Can be used externally (gel) for insect bites. Suitable for children from 1 month (externally), it can be taken by pregnant women from the second trimester if their condition due to allergies causes serious concern. Available in the form of capsules, suspensions, tablets, gel.
Fenkarol. An effective remedy, often used in the fight against seasonal allergies, as well as in blood transfusions. Prescribed to children from 1 year and pregnant women from the 2nd trimester (under medical supervision).
Tavegil. One of the most powerful drugs with long period action (12 hours). Causes drowsiness. Available in tablets and syrup form, it is approved for children from 1 year of age. Pregnant women should not take this medicine.

Suprastin is prescribed for the treatment of seasonal and chronic allergies, urticaria, atopic dermatitis, edema, itching of various etiologies, eczema

Antihistamines 2nd generation

These are improved antihistamines that do not have a sedative effect and have a prolonged effect. You need to take them once a day, the use can be long-term, since these medications are not addictive. Their price is usually low. They are quite effective in treating skin diseases, eliminating Quincke's edema, and are used to alleviate the condition of chicken pox. These medications are not recommended for older people and those with sick heart. Below is a list of the most effective second generation products.

Loratadine. An effective product available in the form of syrup and tablets. Helps fight allergies and their consequences - anxiety, sleep disturbances, weight gain. The medicine can be given to children from three years of age; pregnant women can take the drug in the second and third trimesters. In critical situations, the doctor may prescribe Loratadine up to 12 weeks of pregnancy.
Rupafin. A fairly strong drug that is used in the treatment of skin allergic reactions. The product is safe, acts quickly, and the effect lasts throughout the day. It cannot be used during pregnancy; use by children under 12 years of age is also prohibited. During lactation, Rupafin can be taken only as prescribed by a doctor.
Kestin. The most powerful drug in this group, the effect of which lasts for two days. Used in the most difficult cases, it quickly removes angioedema, relieves suffocation, and reduces skin rashes. At the same time, Kestin is toxic to the liver, so it cannot be taken systematically. It is contraindicated for pregnant women and children under 1 year of age.

Also effective second generation drugs include Claritin, Zodak, Cetrin, Parlazin, Lomiran, Cetrisin, Terfanadine, Semprex.

Important! Long-term use (more than a month) of these drugs is dangerous without a doctor’s permission, especially for powerful drugs. Therefore, do not forget to consult a specialist.

Antihistamines 3rd generation

Third-generation antihistamines are considered the newest, but, in fact, they are an improved version of the second generation. They have the same long-lasting effect, do not have a sedative effect, but are completely harmless to the heart and non-toxic to the liver. Thanks to these properties, they can be taken for a long time (for example, when seasonal allergies, psoriasis, bronchial). These are the safest antihistamines for pregnant women, but you should still consult your doctor before taking them.

Important: Antihistamines during pregnancy can be dangerous in the first trimester, so you should consult with. If there is a threat, then you should refrain from such means if possible. Antihistamines for breastfeeding it is also necessary to coordinate with the pediatrician. If appointed powerful drugs, it makes sense to stop breastfeeding for a while.

3rd generation antihistamines are considered the most powerful and fastest-acting. A list of the names of the best of them is given below.

Telfast (Allegra). A new drug that not only reduces the response of receptors to histamine, but also suppresses the production of this substance. As a result, allergy symptoms disappear very quickly. It works throughout the day and is not addictive when taken for a long time. Children under 12 years of age and expectant mothers cannot use Telfast; it is also contraindicated during lactation.
Cetrizine. This tool often considered to be the fourth generation, in in this case The division into categories is very arbitrary. This is a drug latest generation, which begins to act almost instantly (20 minutes after administration), and you can take tablets once every three days. In the form of syrup, Cetrizine can be given to children from six months of age, but it is contraindicated for pregnant women. If the medicine was prescribed by a doctor during lactation, then feeding should be stopped for the period of treatment for allergies. This drug can be taken for a long time.
Desloratadine. A strong antihistamine and anti-inflammatory agent. In therapeutic doses it is well tolerated, but if the dosage is exceeded, it can lead to dry mouth, increased heart rate, and insomnia. It cannot be taken during pregnancy, but in critical cases (suffocation from bronchospasm, Quincke's edema) it can be treated under the supervision of a doctor.
Xizal. Xyzal and its analogues are effective antihistamines for skin allergies and itching, seasonal allergic manifestations, urticaria and chronic year-round allergies. They have a prolonged effect and relieve allergy symptoms 40 minutes after administration. Xyzal is available in the form of drops and tablets and is safe for children over 2 years of age.

Also to good means third generation can be attributed Desal, Lordestin, Erius, Suprastinex.

Antihistamines 4th generation

Such drugs are a new word in the fight against allergies, since they are practically free of side effects, despite their high efficiency. They are not harmful to the heart, like most earlier antihistamines, do not cause drowsiness or addiction, and are easy to use (taken every 1-3 days). The only contraindication is pregnancy and early age child. As for the disadvantages of fourth generation antihistamines, these are high price medicines.

The most popular and effective means this generation:

Fexofenadine. An effective remedy in the fight against all types of allergies, it is as safe as possible and has virtually no side effects. Available in tablets and syrup form, it can be given to children over 6 years old.
Levocetrizine. Strong remedy, which is used to treat year-round and seasonal allergies, reduces symptoms. It is non-toxic to the liver and heart, so it can be taken for months.

How to choose the best allergy remedy

The best antihistamines are not always the most expensive and modern; it is important to understand how relevant a particular drug is in a certain situation. For example, during an illness accompanied by insomnia or restless sleep, first-generation drugs will be preferable. They will eliminate allergy symptoms, and their sedative effect will be very useful. If an allergy has overtaken a person who does not want to get out of the usual rhythm of life, then he should pay attention to the newest metabolite drugs. In any case, before long-term use of the drug, you should consult your doctor, especially if you need to treat a child or a pregnant woman.