Irritant drugs. Irritants
The number of substances that can cause skin irritation is very large. In contact with living tissues (skin), they cause a feeling of pain (burning, tingling), its redness and an increase in (local) temperature. Moreover, some substances enter into a chemical reaction with living protoplasm (alkalis dissolve proteins, halogens oxidize). Other substances, which are chemically indifferent, 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, some ammonia preparations.
Ammonia solution (ammonia)
Transparent colorless volatile liquid with a pungent characteristic odor - 10% ammonia solution in water. Easily penetrates into tissues, exerting a stimulating effect on the central nervous system (breathing becomes more frequent, blood pressure rises). High concentrations may cause respiratory arrest. It is used to bring the patient out of a fainting state, for which a small piece of cotton wool moistened with ammonia is carefully brought to the nasal openings. Inhalation of it, acting on the receptors of the upper respiratory tract (the end of the trigeminal nerve), has an exciting effect on the respiratory center (excites breathing). Applied inside (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
Peppermint is a cultivated perennial herb that contains an essential oil containing menthol.
An infusion of peppermint leaves (5 g per 200 ml of water) is used internally against nausea and as a choleretic agent.
Peppermint oil is obtained from the leaves and other 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 agent. It is an integral part of the Corvalol preparation. "("Valocordin"). The sedative and antispasmodic effect is associated with the presence of menthol.
Peppermint tablets - used as a sedative and antispasmodic for nausea, vomiting, spasms of smooth muscles, 1-2 tablets per intake under the tongue.
Mint drops - consist of tincture of alcohol mint leaves and peppermint oil. Applied inside 10-15 drops per reception as a remedy for nausea, vomiting, analgesic for neuralgic pain.
Tooth drops, composition: mint oil, camphor, valerian tincture, painkiller.
Menthol
Colorless crystals with a strong mint odor and a 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 the nerve endings, accompanied by a feeling of slight cold, burning, tingling, and has a local analgesic effect. Externally used as a sedative and analgesic for neuralgia, arthralgia (rubbing an alcohol solution, oil suspension, ointments). With migraines, they are used in the form of menthol pencils. In 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 nose drops. Lubrication of the nasopharynx with menthol is contraindicated in young children due to possible reflex inhibition and respiratory arrest. Menthol is an integral part of Zelenin drops.
Validol
A solution of menthol in menthol ester of isovaleric acid. It is used for angina pectoris, as it can, as a result of irritation of the receptors of the oral mucosa, reflexively cause the expansion of the coronary vessels. Used for nausea, neuroses. 2-3 drops per piece of sugar (bread) or tablet - under the tongue for a faster and more complete effect of the drug. Hold until complete resorption.
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 from the calculation: 10 g of leaves are poured into a glass of cold water and boiled over low heat for 15 minutes, cooled, filtered. For rinsing with diseases of the upper respiratory tract, for the treatment of fresh and infected wounds, inflammatory diseases of the female genital organs (lotions, washings) and inhalations: 1 tablespoon per glass of water.
Eucalyptus tincture - inside 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 - mature dried fruits of capsicum.
Capsicum tincture
Applied externally for neuralgia, radiculitis, myositis for rubbing.
Ointment for frostbite
Ingredients: tincture of capsicum, formic alcohol, ammonia solution, camphor oil and castor oil, lanolin, lard, petroleum jelly, green soap. Used to prevent frostbite. Rub a thin layer on the exposed parts of the body.
Pepper plaster
A mass containing an extract of capsicum, belladonna, arnica tincture, natural rubber, pine rosin, lanolin, vaseline oil, applied to a piece of cotton fabric. It is 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 within 2 days, if there is no strong burning sensation. When irritation is removed, the skin is lubricated with petroleum jelly.
Turpentine oil (purified turpentine)
An essential oil obtained by distillation of resin from Scots pine. It has a local irritant, analgesic and antiseptic effect. Applied externally in ointments and liniments for rubbing with neuralgia, myositis, rheumatism, sometimes inside and for inhalation with putrefactive bronchitis, bronchiectasis and other lung diseases. Contraindicated in lesions of the parenchyma of the liver and kidneys.
See also:
Various laxatives.
Magnesia white (basic magnesium carbonate) - 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 each, from 6 to 12 years old - 1-2 g per dose 2-3 times a day. White magnesia is also used externally as a powder and inside - with increased acidity of gastric juice ...
Irritants have been used for a long time. Until now, they are often called distractions. Previously, this concept was invested with the idea that irritants, causing reddening of the skin, thereby divert blood from the internal organs where the pathological process is localized, and this contributes to recovery.
The mechanism of action of irritants is still not entirely clear. There is no doubt that the therapeutic effect of irritants, at least in part, is due to the various reflexes that arise due to irritation of receptors in the skin or mucous membranes.
When applying irritants to any part of the skin, except for a local reaction (burning, redness and other phenomena), there is a reflex excitation of the respiratory and vasomotor centers of the medulla oblongata. 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. With a disease of one or another organ, painful points appear on the skin in certain places (Zakharyin-Ged zones). Irritation of skin areas corresponding to the Zakharyin-Ged zones affects the state of the organs associated with them. However, it should be borne in mind that strong irritations cause reflex effects on very many organs and systems. Such stimuli, by creating streams of nerve impulses in certain nerve trunks, can extinguish pathological nerve impulses that travel along these trunks from the internal organs and maintain their disease state. In addition, strong irritating (damaging) effects cause a response from the internal secretion organs, mainly from the pituitary and adrenal glands, 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 ).
Irritant drugs are usually divided into redness-causing agents (rubifacientia) and abscesses (vesicantia). This division is somewhat arbitrary, since prolonged exposure to redness-causing agents can lead to the formation of blisters.
The group of so-called sclerosing agents can also be attributed to 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, pain reaction with a transition to an anesthetic effect in the future. 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 the muscles and nerves (neuralgia, myositis, lumbago, sciatica), inflammatory processes in the respiratory tract, etc.
Essential oils are often used as irritants. Essential oils are chemically very diverse. Accordingly, the pharmacological properties of essential oils are different. Among them there are expectorants, diuretics, choleretic, socogonal, carminative, diaphoretic, irritating, anti-inflammatory, antiseptic, insecticidal and other agents. The action of many of these agents is associated with their irritating effect on certain cells and tissues.
Of the irritants containing essential oils, mustard preparations are most often used. The synegrin glucoside 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 hydrogen sulfate and glucose. The irritating effect of the butt depends on the essential mustard oil formed during hydrolysis. Dry mustard flour is not irritating. When wetting it with warm water, an 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 can cause the destruction of the myrosin enzyme. Mustard is used in the form of mustard plasters, local mustard baths, mustard wraps.
Turpentine is widely used as an irritant. Turpentine refers to essential oils containing terpenes, among which the main one is 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 the upper parts of the digestive tract causes powerful reflexes, leading to excitation of the respiratory and vasomotor centers. Sniffing ammonia is one of the simplest and at the same time effective methods of helping with fainting. Persons who are in a state of severe intoxication are allowed to drink a few drops of ammonia diluted in half a glass of water.
Bell pepper(ripe fruits of the plant Capsicum annuum) contains capsaicin, which has an irritant effect. Alcohol tincture of pepper is used externally as an irritant and internally as an appetite enhancer.
Blistering irritants (vesicators) include Spanish flies. These are special bugs (Litta vesicatoria) containing cantharidin, which has the ability to cause blisters. Spanish flies are used in the form of a special plaster. When absorbed into the blood, cantharidin can cause general poisoning, accompanied by kidney damage. Recently, pedcalen (alcohol tincture of Pederus caligatus bugs) has found practical application. Vesicatory substances have a therapeutic effect in neuritis (inflammation of the nerves) and neuralgia, as well as in some sluggish inflammatory processes.
Sclerosing agents 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.
Preparations
Mustard - seeds(Semina Sinapis), FVIII. It is used in the form of mustard plasters, which are rectangular sheets of paper coated with defatted powder from mustard seeds (charta sinapisata). Mustard can be used to make ex tempore mustards. It is also used for local (for example, foot) baths. Dry mustard powder is poured into socks in order to cause a reflex effect on the skin of the feet.
Mustard essential oil(Oleum Sinapis aethereum), FVIII (B). 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 to rub the skin.
Turpentine, purified(Oleum Terebinthinae rectificatum), FVIII. Transparent colorless liquid with a peculiar smell, insoluble in water, soluble in organic solvents. It is used in ointments and liniments, as well as for inhalation.
Darmish oil, Darminol(Oleum Cinae, Darminolum). The essential oil obtained from wormwood is a liquid with an aromatic odor. Darminol is used for rubbing the skin with rheumatism, neuritis, neuralgia, myalgia, etc.
Capsicum fruit, red pepper(Fructus Capsici), FVIII. Used to make tincture.
Capsicum tincture(Tinctura Capsici). A clear red liquid with a pungent 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 with a decrease in blood circulation and respiration, in surgery - as an antiseptic for washing hands.
Volatile ointment(Linimentum ammoniatum, Linimentum volatile), FVIII. A mixture of ammonia with sunflower oil, with the addition of a small amount of oleic acid; Homogeneous thickish liquid of yellowish-white color with the smell of ammonia. Used for rubbing the skin.
Spanish fly patch(Emplastrum Cantharidum), FVIII. Soft homogeneous greasy to the touch mass. Used as an irritant that causes blistering.
Spanish fly tincture(Tinctura Cantharidum), FVIII (B). Clear greenish-yellow liquid. It is used externally as an irritant in the form of additions to liniments, is part of liquids that improve hair growth. Inside the tincture is currently not used.
These are substances that, when applied topically, can excite sensitive nerve endings of the skin and mucous membranes, while there is vasodilation, improvement in tissue trophism at the site of drug application, suppression of pain impulses and the appearance of a "distracting" effect in case of pain in the joints, muscles, 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 excite respiration and remove patients from fainting, for which they bring a piece of cotton wool moistened with ammonia to the nose. There is a reflex stimulation of the respiratory center. Sometimes prescribed 5-10 drops in 100 ml of water when intoxicated. Has antimicrobial activity.
mustard plasters- sheets of paper coated with mustard flour obtained from the cake of mustard sarepskaya. When wetted with warm water, there is a strong smell of mustard oil, which has an irritating effect. Used for diseases of the respiratory system, neuralgia, angina pectoris.
Menthol- the main component of peppermint essential oil. It has a strong characteristic odor and a cooling taste. Does not dissolve in water. It has an irritating, distracting, anesthetic, antimicrobial effect. Reflexively reduces vascular tone. They produce menthol oil 1% and 2%, alcohol solution of menthol 1% and 2%, menthol pencil, powder. Included in tablets Validol, Boromenthol ointments, Menovazin liquids, Gevkamen ointments, etc.
They are used for inflammatory diseases of the upper respiratory tract (lubrication, inhalation); neuralgia, joint pain (rubbing into the skin); migraines (rubbing in the temples); angina pectoris (tablets under the tongue).
Irritants used for joint and muscle pain include drugs Camphor(camphor alcohol, camphor oil), turpentine ointment, LS peppercorns o (tincture, pepper patch, Kapsitrin, Kapsin liniment, Nikoflex ointment); PM poisons of snakes and bees(Ointments "Viprosal", "Vipratox", "Apizartron").
Means that excite sensitive receptors and have a reflex effect also include expectorants, emetics, laxatives, bitterness, choleretic and other drugs, which will be discussed in the relevant sections.
| Drug name, synonyms, storage conditions | Release form | Application methods |
| Procainum (Novocainum) | Powder, vial. 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 | Tissue injections (infiltration anesthesia) Injections along the nerve (conduction) Into the rectum |
| Benzocainum (Anaesthesinum) | Powder Tab. 0.3 Suppositories | In ointments, powders 1-2 tablets. 3-4 times a day Into 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, muscle |
| Trimecainum (Mesocainum) | Amp. 2% solution - 1 ml, 2 ml, 5 ml, 10 ml | Injections in layers into the tissue, along the nerve, into the 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. spoon 3-4 times a day |
| Mucilago seminis Lini | Slime 1:30 | In potions |
| "Almagelum" | Flac. 170 ml | 1 table. spoon 3 times a day before meals and at bedtime |
| Carbo activatus (Carbolenum) | Powder Tab. 0.25; 0.5 | Inside, 2-3 tablets. (grinding) 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 contents of the package in the form of a suspension in water |
| Solutio Ammonii caustici | Amp. 10% solution - 1ml Flac. 10% - 10 ml, 40 ml | On cotton for inhalation |
| Mentholum | Powder | Rub in (2% alcohol solution or 10% oil solution) |
| Polyphepanum | Packs of 10.0 | 1 table. 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 injected into inflamed tissues and why?
3. What is the purpose of adding a solution of epinephrine hydrochloride 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 the afferent nerves of the skin and mucous membranes.
Irritants include some synthetic substances and products of plant origin. From synthetic substances R.'s properties with. possess ammonia, formic acid, ethyl alcohol, dichloroethyl sulfide (yperite), trichlorotriethylamine, methyl salicylate, nicotinic acid derivatives (for example, b-butoxyethyl ester of nicotinic acid, ethyl nicotinate), etc. These substances are used as R. with. in various dosage forms intended for external use. for example, ammonia is used in the form of a solution of ammonia (Solutio Ammonii caustici) and ammonia liniment (Linimentum ammoniatum; synonymous with volatile ointment); formic acid - in the form of formic alcohol (Spiritus Acidi formici), which is a mixture of 1 part of formic acid and 19 parts of 70% ethyl alcohol. Dichlorodiethyl sulfide is part of the Psoriasin ointment, trichlorotriethylamine is part of the Antipsoriaticum ointment, b-butoxyethyl ether of nicotinic acid, together with vanillylamide of nonilinic acid, is part of the Finalgon ointment (Unguentum Finalgon), and ethyl nicotinate together with capsaicin, ethylene glycol salicylate and lavender oil - in the composition of the cream Nicoflex (Nicoflex). Methyl salicylate is used per se or mixed with other R. s. as part of a number of dosage forms, for example, Bom-Bengue ointment (Unguentum Boum-Benge), complex methyl salicylate liniment (Linimentum Methylii salicylatis compositum), Sanitas liniment (Linimentum "Sanitas"), salinimentum (Salinimentum).
Of the products of plant origin, many essential oils, some alkaloids, glycosides, saponins, and others have irritating properties. essential oils include peppermint oil and the main active ingredient of this oil is menthol, eucalyptus oil (Oleum Eucalypti), essential mustard oil, purified turpentine oil (synonymous with purified turpentine), camphor, etc.
Essential oils as R. s. used both in pure form and as part of various dosage forms and combined preparations containing essential oils and other plant and synthetic irritants. These drugs include, for example, Efkamon ointment (Unguentum Efcamonum), which includes camphor, clove oil, mustard essential oil, eucalyptus oil, menthol, methyl salicylate, capsicum tincture, thymol, chloral hydrate, cinnamon alcohol, spermaceti and petrolatum; aerosol "Camphomenum" (Aerosolum Camphomenum), containing menthol, eucalyptus, camphor and castor oils, furacilin solution, olive oil. The irritating effect of mustard plasters is due to the presence of essential mustard oil in them.
From the preparations containing alkaloids, as R. page. mainly tincture and extract of capsicum are used, the active substance of which is the alkaloid capsancin. In addition, tincture of capsicum is part of 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). Of the products of plant origin, birch tar and preparations that contain it (for example, balsamic liniment according to Vishnevsky, Wilkinson's ointment) have moderately pronounced local irritating properties.In addition to the indicated R. s. there are drugs belonging to other groups of drugs that have irritant properties and cause certain pharmacological effects in a reflex way by stimulating mucosal 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, bitterness . In R.'s group with. also do not include drugs in which the local irritant effect is not the main, but a side effect.
R.'s mechanisms of action with. not studied enough. It is known that with local application of R. s. cause local tissue irritation, against which pharmacological effects of a reflex and trophic nature can develop.
Besides, R. page. able to relieve pain in the area of affected tissues and organs due to the so-called distracting action.An example of the reflex action of R. s. can serve as a stimulating effect of ammonia solution on respiration. When ammonia vapor is inhaled, a reflex excitation of the respiratory center occurs due to irritation of the receptors of the upper respiratory tract. In addition, ammonia vapors can probably affect the activity of the reticular formation of the brain stem, since. the afferent systems of the trigeminal nerve participate in maintaining its tone, the sensitive 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. The reflex expansion of the coronary vessels of the heart (due to irritation of the receptors of the oral mucosa) also determines the effectiveness of menthol preparations, such as validol, in angina attacks.
Positive trophic influence of R. of page. on the internal organs is carried out, apparently, in various ways, primarily due to skin-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 skin-visceral reflexes may also have the character of axon reflexes. In the mechanism of trophic effects of R. of page. the release of biologically active substances (for example,
histamine) that occurs when the skin is irritated. The trophic effect explains the therapeutic effect of irritants, mainly in diseases of the internal organs (for example, mustard plasters in diseases of the lungs).The diverting action of R. with. manifested by the weakening of pain in the area of the affected organs and tissues. This effect is due to the fact that in the c.n.s. there is an interaction of afferent impulses from the organs affected by the pathological process and from the skin (from the area of impact of 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 the skin
Irritants are medicinal substances that cause irritation of sensitive nerve endings when applied topically. Irritants belong to different classes of chemical compounds. They tend to be highly lipoid soluble, allowing them to penetrate the epidermis and superficial layers and reach sensitive nerve endings.
When irritants 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 some nerve centers (respiratory, vasomotor) or the state of internal organs (changes in blood supply, metabolism). The action of irritants can accelerate the resolution of the inflammatory process and reduce the pain associated with this process (distracting effect). Thus, for example, the action of mustard plasters (see) with and (see) with myositis is explained. Irritants, acting on the mucous membranes of the upper respiratory tract, excite the respiratory and vasomotor centers (see Ammonia). With irritation of the oral mucosa, an expansion of the coronary vessels occurs with (see Validol, Menthol). Under the action of bitterness (see) on the oral cavity, the excitability of the "food center" reflexively increases. Irritation of the gastric mucosa leads to excitation of the vomiting center, which, depending on the intensity of exposure, causes an expectorant or emetic effect (see Expectorants).
Irritants (Dermerethistica) - medicinal substances that, when applied locally, cause irritation of sensitive nerve endings and reflexes characteristic of irritation of this 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 the capillaries and the increase in their permeability, which is explained by the action of histamine on the capillaries, which is released from the cells when irritating agents act on them. The third component is due to the axon reflex. This reflex is carried out within the sensitive axon as a result of the propagation of impulses arising from irritation of the receptors to the vasodilating branches extending from the sensitive nerve fibers to the arterioles of the skin.
In the past, irritants have been used that cause a more intense local reaction with blistering, suppuration, and even necrosis (eg Spanish flies). Such irritants are now practically out of use. However, such a reaction can also occur under the influence of currently used irritants of moderate strength; this happens with excessive duration of their exposure to the skin.
Irritants are used for inflammatory diseases of the 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 underlying tissues and internal organs. According to L. A. Orbeli, these are axon reflexes that spread within the ramifications of sympathetic nerve fibers. It is possible, however, that these reflexes are closed in the spinal cord, and their afferent link is sensory nerve fibers, and the efferent link is sympathetic fibers originating in the lateral horns of the spinal cord. Since the trophic cutaneo-visceral reflexes are segmental in nature, irritants should be applied to the Ged's zones, corresponding to the localization of the inflammatory process. When exposed to irritating agents on extensive skin surfaces, impulses arising in sensitive nerve endings propagate 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 sensitive 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 under the influence of cold. Therefore, application to the skin or mucous membranes of such irritants causes vasoconstriction. The therapeutic effect of such irritants in angina attacks is probably the result of the expansion 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 the surface layers of the epithelium and reach sensitive nerve endings. Good solubility in lipoids is distinguished, in particular, by essential oils widely used as irritants.
Irritating agents that have a selective effect on certain receptors of the digestive tract have a wide practical application. The reflexes that arise in this case depend on the localization of the receptors on which the given irritating agent acts. When the receptors of the oral cavity, which 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 excitation 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).
