Irritating drugs. Irritants
The number of substances that can cause skin irritation is very large. In contact with living tissue (skin), they cause a feeling of pain (burning, tingling), redness and an increase in (local) temperature. Moreover, some substances enter into a chemical reaction with living protoplasm (alkalis dissolve proteins, halogens oxidize). Other chemically indifferent substances act more or less selectively - in small concentrations they predominantly excite the endings of sensory (afferent) nerves. Such substances are used for medicinal purposes; they form a group of special irritants. These include many essential oils and some ammonia preparations.
Ammonia solution (ammonia)
A transparent, colorless, volatile liquid with a sharp, characteristic odor - a 10% solution of ammonia in water. Easily penetrates tissue, having a stimulating effect on the central nervous system (breathing quickens, blood pressure rises). In high concentrations it can cause respiratory arrest. It is used to bring a patient out of a fainting state, for which a small piece of cotton wool moistened with ammonia is carefully brought to the nasal openings. Inhaling it, acting on the receptors of the upper respiratory tract (the endings of the trigeminal nerve), has a stimulating effect on the respiratory center (stimulates breathing). Use internally (2-3 drops) in half a glass of water for acute alcohol poisoning. The solution also has an antimicrobial effect and cleanses the skin well.
Peppermint
A cultivated perennial plant, peppermint contains an essential oil that includes menthol.
An infusion of peppermint leaves (5 g per 200 mg of water) is used internally against nausea and as a choleretic agent.
Peppermint oil is obtained from leaves and other above-ground parts of the plant, contains 50% menthol, about 9% menthol ester with acetic and valeric acids. It is included in rinses, toothpastes, powders as a refreshing and antiseptic. It is an integral part of the drug "Corvalol" "("Valocordin"). The calming and antispasmodic effect is associated with the presence of menthol.
Mint tablets - used as a sedative and antispasmodic for nausea, vomiting, smooth muscle spasms, 1-2 tablets per dose under the tongue.
Mint drops - consist of an alcoholic tincture of mint leaves and mint oil. Used orally, 10-15 drops per dose, as a remedy against nausea, vomiting, and an analgesic for neuralgic pain.
Dental drops, composition: mint oil, camphor, valerian tincture, analgesic.
Menthol
Colorless crystals with a strong mint odor and cooling taste. Obtained from peppermint oil, as well as synthetically. When rubbed into the skin and applied to the mucous membranes, it causes irritation of nerve endings, accompanied by a feeling of slight cold, burning, tingling, and has a local anesthetic effect. Externally used as a sedative and analgesic for neuralgia, arthralgia (rubbing in an alcohol solution, oil suspension, ointments). For migraines, it is used in the form of menthol pencils. For inflammatory diseases of the upper respiratory tract (runny nose, pharyngitis, laryngitis, etc.), menthol is used for lubrication and inhalation, as well as in the form of nasal drops. Lubricating the nasopharynx with menthol is contraindicated in young children due to possible reflex depression and respiratory arrest. Menthol is a component of Zelenin drops.
Validol
A solution of menthol in isovaleric acid menthol ester. It is used for angina pectoris, as it can, as a result of irritation of the receptors in the oral mucosa, reflexively cause dilatation of the coronary vessels. Used for nausea and neuroses. 2-3 drops on a piece of sugar (bread) or a tablet under the tongue for a faster and more complete effect of the drug. Keep until completely absorbed.
Pectusin
Tablets, composition: menthol, eucalyptus oil, sugar, other fillers. Used for inflammatory diseases of the upper respiratory tract. Keep in the mouth until completely absorbed.
Eucalyptus leaf
Dried leaves of cultivated eucalyptus trees. Contains essential oil, organic acids, tannins and other substances. The decoction is prepared at the following rate: 10 g of leaves are poured into a glass of cold water and boiled over low heat for 15 minutes, cooled, and filtered. For rinsing for diseases of the upper respiratory tract, for the treatment of fresh and infected wounds, inflammatory diseases of the female genital organs (lotions, rinsing) and inhalations: 1 tablespoon per glass of water.
Eucalyptus tincture - internally as an anti-inflammatory and antiseptic, sometimes as a sedative, 10-15 drops per glass of water.
Eucalyptus oil, indications are the same, 10-15 drops per glass of water.
Capsicum fruit is the mature dried fruit of the capsicum.
Capsicum tincture
Apply externally for neuralgia, radiculitis, myositis for rubbing.
Frostbite ointment
Ingredients: tincture of capsicum, formic alcohol, ammonia solution, camphor and castor oils, lanolin, lard, petroleum jelly, green soap. Used to prevent frostbite. Rub a thin layer into exposed parts of the body.
Pepper plaster
A mass containing extract of capsicum, belladonna, arnica tincture, natural rubber, pine rosin, lanolin, vaseline oil, applied to a piece of cotton fabric. Used as an anesthetic for radiculitis, neuralgia, myositis, etc. Before applying the patch, the skin is degreased with alcohol, cologne, ether and wiped dry. The patch is not removed for 2 days unless a strong burning sensation is felt. If irritated, remove and lubricate the skin with Vaseline.
Turpentine oil (purified turpentine)
Essential oil obtained by distilling resin from Scots pine. It has a local irritant, analgesic and antiseptic effect. Used externally in ointments and liniments for rubbing for neuralgia, myositis, rheumatism, sometimes internally and for inhalation for putrefactive bronchitis, bronchiectasis and other lung diseases. Contraindicated for lesions of the liver and kidney parenchyma.
See also:
Various laxatives.
White magnesia (basic magnesium carbonate) is a white light powder, practically insoluble in water. As a mild laxative, adults are prescribed 1-3 g, children under one year old - 0.5 g, from 6 to 12 years - 1-2 g per dose 2-3 times a day. White magnesia is also used externally as a powder and internally - for increased acidity of gastric juice...
Irritants have been used for a long time. To this day, they are often called distractions. Previously, this concept included the idea that irritants, causing redness of the skin, thereby distract blood from the internal organs where the pathological process is localized, and thereby contribute to recovery.
The mechanism of action of irritants is still not entirely clear. There is no doubt that the therapeutic effect of irritants is, at least in part, due to a variety of reflexes arising from irritation of receptors in the skin or mucous membranes.
When irritating agents are applied to any area of the skin, in addition to local reactions (burning, redness and other phenomena), reflex excitation of the respiratory and vasomotor centers of the medulla oblongata is observed. In addition, a number of reflexes arise that change the state and function of other internal organs. There are numerous observations indicating that certain areas of the skin are associated with certain internal organs. When a particular organ is diseased, painful points appear on the skin in certain places (Zakharyin-Ged zones). Irritation of the skin areas corresponding to the Zakharyin-Ged zones affects the condition of the organs associated with them. However, it should be borne in mind that strong irritations cause reflex effects on many organs and systems. Such irritations, creating streams of nerve impulses in certain nerve trunks, can extinguish pathological nerve impulses traveling along these same trunks from the internal organs and maintaining their painful state. In addition, strong irritating (damaging) effects cause a response from the internal secretion organs, mainly from the pituitary gland and adrenal gland, expressed in the release of a number of hormones that have a powerful effect on the course of pathological processes (see the section on hormones - general adaptation syndrome ).
Irritants are usually divided into redness-causing agents (rubifacientia) and vesicants (vesicantia). This division is somewhat arbitrary, since prolonged exposure to agents that cause redness can lead to the formation of blisters.
The group of so-called sclerosing agents can also be classified as irritants.
The group of irritants that cause redness includes mustard, pepper, turpentine, ammonia, camphor, as well as alcohol, ether, tincture of iodine (the latter are discussed in the relevant sections). The application of these substances to the skin causes redness, a feeling of heat, burning, and a painful reaction, which later turns into an anesthetic effect. The effect is due to the fact that irritating substances, penetrating the skin, affect the sensitive endings. A certain role is assigned to the release of histamine occurring in the skin. With prolonged exposure to irritants, in addition to redness, swelling and blisters form on the skin, which is undesirable. Therefore, the use of irritants in unconscious persons requires careful monitoring.
Indications for the use of irritants in this group are diseases of muscles and nerves (neuralgia, myositis, lumbago, sciatica), inflammatory processes in the respiratory tract, etc.
Preparations containing essential oils are often used as irritants. Essential oils are chemically very diverse. In accordance with this, the pharmacological properties of essential oils are different. Among them are expectorants, diuretics, choleretic, socogonics, carminatives, diaphoretics, irritants, anti-inflammatory, antiseptic, insecticidal and other agents. The action of many of these drugs is associated with their irritating effect on certain cells and tissues.
Of the irritants containing essential oils, mustard preparations are most often used. The glucoside sinegrin present in mustard seeds is hydrolyzed under the influence of the enzyme myrosin in the presence of water to form essential mustard oil (allyl isothiocyanate), potassium acid sulfate and glucose. The irritating effect of the stick depends on the essential mustard oil formed during hydrolysis. Dry mustard flour has no irritating effect. When wetting it with warm water, the enzymatic process quickly begins, leading to the formation of essential mustard oil, and the mustard becomes active. It is not recommended to brew mustard flour with too hot water due to the fact that this may cause the destruction of the myrosin enzyme. Mustard is used in the form of mustard plasters, local mustard baths, and mustard wraps.
Turpentine is widely used as an irritant. Turpentine is an essential oil containing terpenes, the main one being pinene. Turpentine is used for rubbing the skin in its pure form, in ointments and liniments.
The active principle of Darmin oil, used for rubbing the skin, is also terpenes, which have an irritating effect.
The irritating properties of ammonia are used to affect the skin (rubbing with various liniments containing ammonia) and mucous membranes. Irritation of the mucous membranes of the upper respiratory tract or upper parts of the digestive tract causes powerful reflexes leading to excitation of the respiratory and vasomotor centers. Snorting ammonia is one of the simplest and at the same time effective methods of helping with fainting. Persons who are heavily intoxicated are given a few drops of ammonia diluted in half a glass of water to drink.
Bell pepper(ripe fruits of the Capsicum annuum plant) contains capsaicin, which has an irritating effect. An alcoholic tincture of pepper is used externally as an irritant and internally as an appetite improver.
Irritating substances that cause blistering (vesicatory substances) include Spanish flies. These are special bugs (Litta vesicatoria) containing cantharidin, which has the ability to cause the formation of blisters. Spanish flies are used as a special patch. When absorbed into the blood, cantharidin can cause general poisoning, accompanied by kidney damage. Recently, pedkalen (an alcohol tincture of Pederus caligatus beetles) has found practical application. Vesicatory substances have a therapeutic effect for neuritis (inflammation of the nerves) and neuralgia, as well as for some low-grade inflammatory processes.
Sclerosants cause the formation of fibrous connective tissue at the injection site. They are used for injection into varicose veins. For these purposes, salts of some high molecular weight unsaturated fatty acids are used.
Drugs
Mustard - seeds(Semina Sinapis), FVIII. It is used in the form of mustard plasters, which are rectangular sheets of paper coated with low-fat powder from mustard seeds (charta sinapisata). Mustard plasters can be prepared ex tempore from mustard. It is also used for local (for example, foot) baths. Dry mustard powder is poured into socks to cause a reflex effect on the skin of the feet.
Mustard essential oil(Oleum Sinapis aethereum), FVIII (B). A transparent, colorless or light yellow liquid with a pungent odor, highly irritating to mucous membranes and causing lacrimation, soluble in alcohol and other organic solvents. It is used to make mustard alcohol.
Mustard alcohol(Spiritus Sinapis) - 2% solution of essential mustard oil in alcohol, used for rubbing the skin.
Purified turpentine(Oleum Terebinthinae rectificatum), FVIII. A transparent, colorless liquid with a peculiar odor, insoluble in water, soluble in organic solvents. It is used in ointments and liniments, as well as for inhalations.
Darmshshy oil, darminol(Oleum Cinae, Darminolum). The essential oil obtained from cypress wormwood is a liquid with an aromatic odor. Darminol is used for rubbing the skin for rheumatism, neuritis, neuralgia, myalgia, etc.
Capsicum fruit, red pepper(Fructus Capsici), FVIII. Used to make tincture.
Capsicum tincture(Tinctura Capsici). Transparent red liquid with a burning taste. It is used internally in drops and externally for rubbing per se, in ointments and liniments.
Ammonia(Ammonium causticum solutum), FVIII - 10% ammonia solution. It is used in liniments for rubbing, as well as for inhalation during a decline in blood circulation and respiration, in surgery - as an antiseptic for washing hands.
Flying ointment(Linimentum ammoniatum, Linimentum volatile), FVIII. A mixture of ammonia with sunflower oil, with the addition of a small amount of oleic acid; homogeneous thick liquid of yellowish-white color with the smell of ammonia. Used for rubbing the skin.
Spanish fly patch(Emplastrum Cantharidum), FVIII. Soft homogeneous fatty mass to the touch. Used as an irritant that causes blistering.
Spanish fly tincture(Tinctura Cantharidum), FVIII (B). Transparent liquid of greenish-yellow color. It is used externally as an irritant in the form of additions to liniments, and is part of liquids that improve hair growth. The tincture is not currently used internally.
These are substances that, when applied topically, can excite sensitive nerve endings of the skin and mucous membranes, thereby dilating blood vessels, improving tissue trophism at the site of drug application, suppressing pain impulses and creating a “distracting” effect for pain in joints, muscles, and internal organs. The mechanism of the “distracting” action is associated with the suppression of the painful reflex by impulses resulting from exposure to an irritating substance.
These substances can also have a general effect on the body, for example, they stimulate the formation and release of enkephalins and endorphins, which are involved in the regulation of pain; stimulate the formation of other endogenous biologically active substances.
Irritants are used mainly externally for neuralgia, radiculitis, arthrosis, rheumatism, bruises, injuries, as well as for rhinitis, pharyngitis, tracheitis, etc.
Ammonia solution– a volatile liquid with a characteristic odor. It is used to stimulate breathing and bring patients out of fainting states, for which a piece of cotton wool moistened with ammonia is brought to the nose. Reflex stimulation of the respiratory center occurs. Sometimes 5-10 drops are prescribed in 100 ml of water for intoxication. Has an antimicrobial effect.
Mustard plasters– sheets of paper coated with mustard flour obtained from Sarep mustard cake. When moistened with warm water, a strong smell of mustard oil is felt, which has an irritating effect. Used for respiratory diseases, neuralgia, angina.
Menthol– the main component of peppermint essential oil. It has a strong characteristic odor and cooling taste. Does not dissolve in water. It has an irritating, distracting, anesthetic, and antimicrobial effect. Reflexively reduces vascular tone. They produce menthol oil 1% and 2%, menthol alcohol solution 1% and 2%, menthol pencil, powder. Included in tablets Validol, Boromenthol ointments, Menovazin liquids, Gevkamen ointments, etc.
Used for inflammatory diseases of the upper respiratory tract (lubrication, inhalation); neuralgia, joint pain (rubbed into the skin); migraines (rubbed in the temple area); angina pectoris (tablets under the tongue).
Irritants used for joint and muscle pain include drugs Camphor(camphor alcohol, camphor oil), turpentine ointment, PM pepper capsicum o (tincture, pepper patch, Capsitrin, liniment Capsin, Nicoflex ointment); Medicines of poisons of snakes and bees(ointments “Viprosal”, “Vipratox”, “Apizartron”).
Drugs that excite sensitive receptors and have a reflex effect also include expectorants, emetics, laxatives, bitters, choleretic and other drugs, which will be described in the relevant sections.
| Drug name, synonyms, storage conditions | Release forms | Methods of application |
| Procainum (Novocainum) | Powder, bottle. 0.25%,0.5% solution – 200 ml and 400 ml; Amp. 0.25%,0.5%,1%, 2% solution – 1 ml, 2 ml, 5 ml, 10 ml Suppositories 0.1 | Injections into tissue (infiltration anesthesia) Injections along the nerve (conductor) Into the rectum |
| Benzocainum (Anaesthesinum) | Powder Table 0.3 Suppositories | In ointments, powders 1-2 tablets. 3-4 times a day In the rectum |
| Lidocainum (Xylocainum) | Amp. 1%, 2%, 10% solution – 2 ml, 10 ml, 20 ml | Injections in layers into the tissue along the nerve, into a vein, into a muscle |
| Trimecainum (Mesocainum) | Amp. 2% solution – 1 ml, 2 ml, 5 ml, 10 ml | Injections in layers into the tissue, along the nerve, into a vein, muscle |
| Articainum (Ultracainum) | Amp. 1%, 2% solution – 5 ml Amp. 5% solution – 2 ml | For infiltration, conduction anesthesia For spinal anesthesia |
| Tanninum | Powder | For the preparation of solutions and ointments |
| Xeroformium | Powder | In the form of ointments, powders |
| Infusum radicis Althaeae | Infusion 1:30 | 1-2 tables each. spoon 3-4 times a day |
| Mucilago seminis Lini | Slime 1:30 | In potions |
| "Almagelum" | Flak. 170 ml | 1 table each. spoon 3 times a day before meals and before bed |
| Carbo activatus (Carbolenum) | Powder Table 0.25; 0.5 | Inside, 2-3 tablets. (crushing) 3-4 times a day (for flatulence) 20-30g per 10-15l of water (for gastric lavage) |
| Belosorbum | Packages 23.0 | |
| Smecta | Packages 3.0 | Inside the package contents in the form of a suspension in water |
| Solutio Ammonii caustici | Amp. 10% solution – 1 ml bottle. 10% – 10 ml, 40 ml | On cotton wool for inhalation |
| Mentholum | Powder | Rub in (2% alcohol solution or 10% oil solution) |
| Polyphepanum | Packages of 10.0 | 1 table each. spoon 3 times a day in 1 glass of water |
Control questions
1.What is the principle of action of anesthetic substances? Types of anesthesia.
2. How does the effect of local anesthetics change when introduced into inflamed tissues and why?
3.For what purpose is epinephrine hydrochloride solution added to anesthetic substances?
4.What is the mechanism of action of astringents? Their application.
5.What is the mechanism of action of activated carbon in case of poisoning?
6.Local and reflex action of irritants. Their application.
7.Explain the mechanism of action of ammonia solution on respiration.
Irritants- drugs, the pharmacological action of which is mainly due to the stimulating effect on the endings of afferent nerves of the skin and mucous membranes.
Irritants include some synthetic substances and herbal products. Of synthetic substances with the properties of R. s. possess ammonia, formic acid, ethyl alcohol, dichloroethyl sulfide (mustard gas), trichlorotriethylamine, methyl salicylate, nicotinic acid derivatives (for example, b-butoxyethyl ester of nicotinic acid, ethyl nicotinate), etc. These substances are used as R. s. in various dosage forms intended for external use. for example, ammonia is used in the form of ammonia solution (Solutio Ammonii caustici) and ammonia liniment (Linimentum ammoniatum; synonym volatile ointment); formic acid - in the form of formic alcohol (Spiritus Acidi formici), which is a mixture of 1 part formic acid and 19 parts of 70% ethyl alcohol. Dichlordiethyl sulfide is included in the Psoriasin ointment, trichlorotriethylamine is included in the Antipsoriaticum ointment, b-butoxyethyl ester of nicotinic acid together with nonilinic acid vanillyl amide is included in the Finalgon ointment (Unguentum Finalgon), and ethyl nicotinate together with capsaicin, ethylene glycol salicylate and lavender oil - in the composition of Nicoflex cream. Methyl salicylate is used per se or in mixture with other R. s. as part of a number of dosage forms, for example Bom - Benge ointment (Unguentum Boum - Benge), complex methyl salicylate liniment (Linimentum Methylii salicylatis compositum), liniment "Sanitas" (Linimentum "Sanitas"), salinimentum (Salinimentum).
Of the products of plant origin, many essential oils, some alkaloids, glycosides, saponins, etc. have irritating properties. essential oils include peppermint oil and the main active ingredient of this oil - menthol, eucalyptus oil (Oleum Eucalypti), essential mustard oil, purified turpentine oil (synonym purified turpentine), camphor, etc.
Essential oils as R. s. used both in pure form and as part of various dosage forms and combination preparations containing essential oils and other plant and synthetic irritants. Such drugs include, for example, Efkamon ointment (Unguentum Efcamonum), which contains camphor, clove oil, essential mustard oil, eucalyptus oil, menthol, methyl salicylate, tincture of capsicum, thymol, chloral hydrate, cinnamon alcohol, spermaceti and petrolatum; aerosol "Camphomenum" (Aerosolum Camphomenum), containing menthol, eucalyptus, camphor and castor oils, furatsilin solution, olive oil. The irritating effect of mustard plasters is due to the presence of essential mustard oil.
From preparations containing alkaloids, as R. s. They mainly use tincture and extract of capsicum, the active ingredient of which is the alkaloid capsancin. In addition, tincture of capsicum is included in the ointment for frostbite (Unguentum contra congelationem), capsitrin (Capsitrinum),
pepper-ammonia liniment (Linimentum Capsici ammoniatum), pepper-camphor liniment (Linimentum Carsici camphralum), and capsicum extract - in the composition of pepper plaster (Emplastrum Capsici). Among products of plant origin, birch tar and preparations containing it (for example, balsamic liniment according to Vishnevsky, Wilkinson’s ointment) have moderately expressed local irritating properties.In addition to the indicated R. s. There are drugs belonging to other groups of drugs that have irritating properties and cause certain pharmacological effects in a reflex way due to stimulation of mucous membrane receptors. For example, drugs that cause a reflex increase in the secretion of bronchial glands belong to expectorants reflex type of action; drugs that cause a laxative effect - to laxatives ; drugs that simulate bile secretion - to choleretic agents ; appetite stimulants - to bitterness . To the group R. s. They also do not include drugs in which the local irritant effect is not the main one, but a side effect.
Mechanisms of action of R. s. insufficiently studied. It is known that with local application of R. s. cause local tissue irritation, against the background of which pharmacological effects of a reflex and trophic nature can develop.
In addition, R. s. are able to relieve pain in the area of affected tissues and organs due to the so-called distracting effect.An example of a reflex action of R. s. The stimulating effect of ammonia solution on respiration may serve. When inhaling ammonia vapor, a reflex excitation of the respiratory center occurs due to irritation of the receptors of the upper respiratory tract. In addition, ammonia vapor may possibly influence the activity of the reticular formation of the brain stem, because in maintaining its tone, the afferent systems of the trigeminal nerve are involved, the sensory endings of which are partially localized in the upper respiratory tract. This explains the effectiveness of inhalation of ammonia solution vapors in respiratory depression and fainting states. The reflex expansion of the coronary vessels of the heart (due to irritation of the receptors in the oral mucosa) is also responsible for the effectiveness of menthol preparations, such as validol, in angina attacks.
Positive trophic influence of R. s. on internal organs is apparently carried out in various ways, primarily due to cutaneous-visceral reflexes, the central links of which are located in the spinal cord. The afferent link of such reflexes is the cutaneous afferent nerves, and the efferent link is the sympathetic nerves emanating from the corresponding segments of the spinal cord. It is possible that some visceral skin reflexes may also have the character of axon reflexes. In the mechanism of trophic effects of R. s. The release of biologically active substances (for example,
histamine), which occurs when the skin is irritated. The trophic effect explains the therapeutic effect of irritants, mainly for diseases of internal organs (for example, mustard plasters for lung diseases).Distractive action of R. s. manifested by a weakening of pain in the area of affected organs and tissues. This effect is due to the fact that in the central nervous system. There is an interaction of afferent impulses from organs affected by the pathological process and from the skin (from the area of exposure to R. s.), as a result of which the perception of pain weakens. In physiological experiments, the possibility of this kind of interaction of nerve impulses entering the central nervous system. on somatic and visceral afferent systems, has been proven in relation to nerve centers located both in the spinal cord and in the brain. Based on this hypothesis, in order to obtain a distracting effect in diseases of the internal organs of R. s. should be applied to areas of skin appropriate
Irritants are medicinal substances that, when applied topically, cause irritation of sensitive nerve endings. Irritants belong to different classes of chemical compounds. They are generally highly soluble in lipids, allowing them to penetrate the epidermis and superficial layers and reach sensitive nerve endings.
When irritating agents are applied to the skin and mucous membranes, a local reaction is observed in the form of hyperemia and swelling, as well as reflexes characteristic of irritation of this receptor field. The therapeutic effect of irritants is explained by the occurrence of reflexes that lead to changes in the activity of certain nerve centers (respiratory, vasomotor) or the state of internal organs (changes in blood supply, metabolism). The action of irritants can speed up the resolution of the inflammatory process and reduce the pain associated with this process (distracting effect). Thus, for example, the effect of mustard plasters (see) in and (see) in myositis is explained. Irritants, acting on the mucous membranes of the upper respiratory tract, stimulate the respiratory and vasomotor centers (see Ammonia). When the mucous membrane of the oral cavity is irritated, dilatation of the coronary vessels occurs (see Validol, Menthol). When bitterness (see) acts on the oral cavity, the excitability of the “food center” reflexively increases. Irritation of the gastric mucosa leads to stimulation of the vomiting center, which, depending on the intensity of the effect, causes an expectorant or emetic effect (see Expectorants).
Irritants (Dermerethistica) are medicinal substances that, when acted locally, cause irritation of sensitive nerve endings and reflexes characteristic of irritation of a given receptor field. Under the influence of irritating agents, a local reaction develops on the skin, consisting of three components (“triple reaction”): bright hyperemia and swelling at the site of direct exposure to irritating agents and a rim of more moderate hyperemia surrounding this place. The first two components of this reaction depend on the expansion of capillaries and an increase in their permeability, which is explained by the action of histamine on the capillaries, which is released from the cells when exposed to irritating agents. The third component is due to the axon reflex. This reflex occurs within the sensory axon as a result of the spread of impulses arising from receptor irritation to vasodilator branches extending from the sensory nerve fibers to the arterioles of the skin.
Previously, irritants were used that caused a more intense local reaction with the formation of blisters, suppuration and even necrosis (for example, Spanish flies). Such irritants are now practically out of use. However, a similar reaction can also occur under the influence of currently used irritants of moderate strength; this happens when their exposure to the skin is prolonged for too long.
Irritants are used for inflammatory diseases of internal organs, as well as for myositis, neuritis, arthralgia, etc. (see Mustard plasters, Ammonia, Turpentine). Under the influence of irritants, the resolution of the inflammatory process is accelerated and the pain associated with this process is weakened. The therapeutic effect of irritants is explained by segmental trophic reflexes from the skin to the underlying tissues and internal organs. According to L. A. Orbeli, these are axon reflexes that spread within the branches of sympathetic nerve fibers. It is possible, however, that these reflexes are closed in the spinal cord, with their afferent link being sensory nerve fibers, and their efferent link being sympathetic fibers originating in the lateral horns of the spinal cord. Since trophic cutaneous-visceral reflexes are segmental in nature, irritating agents should be applied to the Ged zones corresponding to the localization of the inflammatory process. When exposed to irritants on large surfaces of the skin, impulses arising in sensory nerve endings spread to the suprasegmental parts of the central nervous system, in particular to the respiratory and vasomotor centers of the medulla oblongata. This is the basis for the use of mustard wraps for vascular and respiratory failure. Reflexes to the respiratory and vasomotor centers also occur when sensory receptors in the nasal mucosa are irritated. Ammonia is used as a means to irritate these receptors.
Some irritants have a selective effect on receptors that perceive the sensation of cold (see Validol, Menthol). Under the influence of such irritants, reflexes of the same nature arise as when exposed to cold. Therefore, application of such irritants to the skin or mucous membranes causes vasoconstriction. The therapeutic effect of such irritants during angina attacks is probably the result of dilation of the coronary vessels as a result of irritation of cold receptors in the oral mucosa.
Irritants are found in various classes of chemical compounds. As a rule, irritants are distinguished by a common physicochemical feature - solubility in lipoids, which allows them to penetrate the epidermis and surface layers of the epithelium and reach sensitive nerve endings. In particular, essential oils, which are widely used as irritants, are characterized by good solubility in lipoids.
Irritants that have a selective effect on certain receptors of the digestive tract are widely used in practice. The reflexes that arise depend on the location of the receptors on which the irritating agent acts. When the receptors in the oral cavity that perceive the sensation of bitter taste are irritated, a reflex increase in the excitability of the “food center” occurs (see Bitterness). Irritation of receptors in the gastric mucosa leads to reflex stimulation of the vomiting center, which, depending on the intensity of irritation, causes expectorant or emetic effects (see Expectorants). Irritation of receptors in the intestinal mucosa leads to a reflex increase in its peristalsis (see Laxatives).
