Subject: " Irritants"
Plan:
1) general characteristics irritants.
2) Mechanism of action.
3) The mechanism of reflexive, “distracting” action.
4) Classification.
5) Application.
Irritants include drugs that excite the endings of afferent nerves, causing reflex and local effects: redness of the skin, improvement of blood supply, tissue trophism, reduction of pain and inflammation. Apply externally in the form of rubbing, ointments, balms, nasal drops.
Mechanism of action: irritate, excite the endings of afferent nerves (receptors) embedded in the skin, which selectively respond to certain types irritations (pain, temperature). As a result, local (local) release of autocoids occurs, biologically active substances(kinins, histamine, prostaglandins), which have a local vasodilator, hyperemic (cause redness) effect with improved tissue nutrition and improved blood circulation. In this case, deep blood vessels (for example, coronary vessels) reflexively dilate. As a result of the “distracting” effect of irritants, pain in areas of inflammation decreases or completely disappears.
Mechanism of reflexive, “distracting” action: p When there is inflammation, pain impulses continuously enter the corresponding segment spinal cord, from there they enter the higher parts of the central nervous system, where they create a focus of persistent excitation nerve centers, the so-called “pain dominant focus”. When an irritating agent is applied to the corresponding area of the skin, a new stream of impulses of a different nature arises. A new dominant focus of excitation is created in the central nervous system, and the old one fades away, painful sensations weaken or disappear altogether. Therefore, irritants are applied to the area of the skin that receives afferent innervation from the same segment of the spinal cord as the diseased organ.
Classification:
1.Irritants containing essential oils of plants:
A) Menthol preparations from peppermint leaves:
“Validol” tablets, “Pinosol” nasal drops (menthol and pine oil),
peppermint tincture, 10% oil solution menthol, alcohol solution "Menovazin" (menthol, novocaine, anesthesin).
Menthol preparations, when applied to the mucous membranes and skin, stimulate cold receptors, cause a feeling of cold, a reflex narrowing of the surface blood vessels and weakening of pain sensitivity at the site of application. However, the tone of blood vessels and smooth muscles of deep-lying organs may expand. The mechanism of action of Validol tablets is based on this. It is taken sublingually; the menthol it contains irritates the cold receptors of the oral mucosa, which causes reflex expansion coronary vessels and reduction of heart pain. Used for pain in the heart from spasm of the coronary vessels during mild attacks of angina.
Mint tincture is taken orally, 15-20 drops per ¼ glass of water for spasms of the biliary tract. An oily 10% menthol solution is instilled into the nose for rhinitis to reduce inflammation and facilitate nasal breathing. Ointments containing 1-2% menthol and Menovazin are used for skin diseases accompanied by itching, for rubbing for neuralgia, muscle and joint pain, migraines (rubbed into the temples) as well as other irritants.
B) Combined drugs:
aerosols "Inhalipt"(streptocide, norsulfazole, eucalyptus oil, peppermint oil); "Kameton" ( camphor, menthol, Eucalyptus oil), ointments "Efkamon", "Gevkamen" ( menthol, camphor, clove oil, eucalyptus), "Ben-gay"(menthol, methyl salicylate), "Bom-benge"(camphor, menthol, eucalyptus oil).
Capsaicin is isolated from the fruits of capsicum, which is part of combined ointments. "Espol", "Captrine", "Nicoflex", tinctures of capsicum, pepper plaster. Pepper patch is used for longer effects.
The glycoside sinigrin, which is part of mustard plasters, is isolated from mustard seeds. Mustard plasters are wetted only warm water, because When it is hot, sinegrin is inactivated, when it is cold it is not activated, and when it is warm it breaks down to form the irritating substance allyl thiocyanate. When applied to calf muscles, mustard plasters cause a reflex expansion of the coronary vessels and lower blood pressure; as a distracting agent, they are applied between the shoulder blades for chest pain with bronchitis, for a sore throat in the back of the head and throat, for muscle pain on the lumbar region and ribs, with some gynecological diseases to the area below the navel.
Purified turpentine essential oil (turpentine) is obtained by distilling Scots pine resin and used independently, as part of turpentine ointment and other ointments.
bee venom “Apizatron”, “Apifor”, “Ungative”;
snake venom “Viprasal”, “Vipraxin”, “Nayatox”, “Nayaksin”.
3.Synthetic irritants:
ammonia solution 10% (ammonia), used for fainting, apply 1-2 drops to a cotton swab and give the patient a sniff, this irritates the receptors of the upper respiratory tract, which reflexively excites the central nervous system and consciousness returns.
For rubbing use formic alcohol, ointments "Kapsikam" "Finalgon"(butoxyethyl ether nicotinic acid). Finalgon is applied in a small amount, no more than a pea, distributed on the skin with a special applicator, and in case of severe pain, removed with a dry cloth.
Application: V complex treatment arthritis, myositis, neuritis, neuralgia, acute and chronic diseases lungs, used to treat bedsores camphor alcohol to improve local blood circulation.
Side effects:
with prolonged contact of irritating agents with the skin, a burn with subsequent inflammation is possible, therefore, if severe pain occurs, it is necessary to stop using the drug.
Control questions to secure:
1. How does the mechanism of action of irritating agents differ from enveloping, astringent, and adsorbent agents?
2. Which ones are produced? combination drugs menthol?
3. What is the peculiarity of the action of menthol preparations?
4.What is the essence of the distracting effect of irritants?
5.What precautions should be taken when using irritants?
Recommended reading:
Mandatory:
1.V.M.Vinogradov, E.B. Katkova, E.A. Mukhin “Pharmacology with prescription”, textbook for pharmaceutical schools and colleges / edited by V.M. Vinogradov-4th edition - St. Petersburg: Special. Lit., 2006-864 pp.: ill.
Additional:
1. M.D. Gaevy, P.A. Galenko-Yaroshevsky, V.I. Petrov, L.M. Gaevaya “Pharmacology with prescription”: Textbook. – Rostov n/d: publishing center “MarT”, 2006 – 480 p.
2.M.D. Mashkovsky “Medicines” - 16th ed., revised.. corrected. And additional - M.: New Wave: Publisher Umerenkov, 2010. - 1216 p.
3. Directory VIDAL, Medicines in Russia: Directory. M.: AstraFarmService, 2008 - 1520 p.
4.Atlas medicines. – M.: SIA International LTD. TF MIR: Eksmo Publishing House, 2008. – 992 p., ill.
5. N.I. Fedyukovich Guide to medicines: at 2 o'clock. Ch. P.. - Mn.: Interpressservice; Book House, 2008 – 544 p.
6. D.A. Kharkevich Pharmacology with general formulation: Textbook for medical schools and colleges. – M,: GEOTAR – MED, 2008, - 408 p., ill.
Electronic resources:
1.Electronic library for the discipline. Lecture on the topic “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 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 in 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 becomes more frequent, blood pressure). 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 (ends trigeminal nerve), has a stimulating effect on respiratory center(excites breathing). Apply orally (2-3 drops) in half a glass of water at acute poisoning alcohol. The solution also has an antimicrobial effect and cleanses the skin well.
Peppermint
Cultivated perennial peppermint, contains essential oil, which contains 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 the leaves and other aerial plant parts, contains 50% menthol, about 9% menthol ester with acetic and valeric acids. Included in rinses, toothpastes, powders as a refreshing and antiseptic. Is integral part 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, painkiller.
Menthol
Colorless crystals with strong odor mint 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. At inflammatory diseases 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 for children early age 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 rate of: 10 g of leaves pour into a glass cold water and boil over low heat for 15 minutes, cool, filter. 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: capsicum tincture, formic alcohol, ammonia solution, camphor oil and castor oil, lanolin, lard, Vaseline, green soap. Used to prevent frostbite. Rub a thin layer into exposed parts of the body.
Pepper plaster
Mass containing extract capsicum, belladonna, arnica tincture, natural rubber, pine rosin, lanolin, petroleum jelly, 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 are drugs that cause local application irritation of sensitive nerve endings. Irritants belong to different classes 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. Therapeutic effect irritants are 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 resolution inflammatory process and reduce the pain associated with this process (distraction 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). With the action of bitterness (see) on, 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 irritating agents 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 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.
Wide practical use have irritants that have a selective effect on certain receptors digestive tract. 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).
Irritants, causing depolarization of sensitive nerve endings, have a local irritating effect, which is accompanied by reflex reactions (blood supply and tissue trophism are improved, pain is reduced).
Drugs in this group are characterized by local, reflex and neurohumoral effects.
TYPES OF ACTION
Local irritation is manifested by pain, hyperemia and swelling at the site of application of the drugs. Irritants directly excite nerve endings and also release histamine, serotonin, bradykinin and prostaglandins. These autacoids have an irritating effect and dilate blood vessels. Hyperemia develops not only in the area of application of irritants, but also spreads to adjacent areas of the skin through the axon reflex mechanism.
With prolonged contact of strong irritants with the skin, contact with mucous membranes and damaged areas of the skin, strong pain and inflammatory response.
Irritants are used for neuralgia, radiculitis, lumbago, sciatica, arthritis, myositis, bursitis, tendovaginitis, muscle and ligament injuries, peripheral circulation disorders, tracheitis, bronchitis. Sometimes irritants are rubbed into the skin to warm up the muscles before physical exercise and sports competitions.
Irritants are of plant and synthetic origin.
IRRITANTS OF PLANT ORIGIN
MENTHOL is a terpene alcohol from peppermint. Has a selective stimulating effect on cold receptors, causing a feeling of cold, followed by local anesthesia. Irritation of cold receptors in the oral cavity by menthol is accompanied by sedative, antiemetic effects and reflex dilation of coronary vessels during angina pectoris. The menthol drug VALIDOL (25% solution of menthol in the menthyl ester of isovaleric acid) is used for neurosis, hysteria, sea and air sickness, to relieve a mild attack of angina.
Menthol is included in ointments with irritating effect(BOMBENGE, BOROMENTHOL, EFKAMON), the drug MENOVAZIN.
MUSTARD - paper coated with a thin layer of low-fat mustard containing the glycoside sinigrin. After wetting the mustard plaster with water at a temperature of 37 - 40 ° C, the enzyme myrosin is activated, which breaks down sinigrin and releases the active irritant - essential mustard oil (allyl isothiocyanate).
PEPPER FRUITS, containing capsaicin, are used in the composition of CAPPIPER TINCTURE, PEPPER PATCH, NICOFLEX cream. Capsaicin, like the mediators of the cannabinoid antinociceptive system (anandamide, 2-arachidonylglycerol), is an agonist of vanilloid cytoreceptors (VR]) in the central nervous system.
PURIFIED TERPENTINE OIL - a product of distillation of resin from Scots pine, contains a lipophilic substance with a terpene structure - a-pinene; is part of TURPENAL OINTMENT, SANITAS liniment.
When large skin surfaces are irritated, as well as when the stimulus is strong, a reflex excitation of breathing occurs, an increase blood pressure, changes in heart rhythm. These reflexes are central, because close in the vital centers of the medulla oblongata (respiratory, vasomotor, n. vagus center). Central reflexes when applied irritants used to stimulate the central nervous system (with fainting; mustard baths, mustard wrapping in pediatrics for pneumonia; rubbing the patient’s entire body with irritating substances when exposed to low temperatures).
When irritating substances are applied to the skin, trophic reflexes may also occur, i.e. nervous influences, changing metabolic processes in certain tissues. The spinal cord is characterized by segmentation.
Classification of cholinergic receptors and cholinergic drugs. Cholinomimetics. Mechanism of action, pharmacological effects. Indications for use. Complications and measures of assistance. Toxicology of nicotine.
Classification.
Drugs affecting m- and n-cholinergic receptors:
M-,n-cholinomimetics: - carbacholine.
M-,n-anticholinergics: - cyclodol.
2.Anticholinesterase drugs:
Reversible action: - physostigmine salicylate; - prozerin; - galantamine hydrobromide; - pyridostigmine bromide.
Irreversible action: - armin.
3. Cholinesterase reagents:- dipyroxime; - isonitrosine; - alloxime
4.Medicines affecting m-cholinergic receptors:
M-cholinomimetics: - pilocarpine hydrochloride; - aceclidine
M-anticholinergics: -atropine sulfate; -scopolamine hydrobromide; -platiphylline hydrotartrate; -metacin; -homatropine hydrobromide; - belladonna extract; -pirenzepine; - ipratropium bromide.
5.Drugs affecting n-cholinergic receptors:
N-cholinomimetics: -cytiton; -lobeline hydrochloride.
N-anticholinergics:
Ganglion blocking agents: - benzohexonium; -pentamine; -hygronium; -pyrylene; -arfonad.
Curarepods (muscle relaxants): - tubocurarine chloride; -pancuronium bromide; -pipecuronium bromide; -ditilin; -mellictin.
In cholinergic synapses (parasympathetic nerves, preganglionic sympathetic fibers, ganglia, all somatic) the transmission of excitation is carried out by the mediator acetylcholine. Acetylcholine is formed from choline and acetylchoenzyme A in the cytoplasm of the endings of cholinergic nerves.
Cholinergic receptors excited by acetylcholine have unequal sensitivity to certain pharmacological agents. This is the basis for the identification of the so-called: 1) muscarine-sensitive and 2) nicotine-sensitive cholinergic receptors, that is, M- and N-cholinergic receptors. M-cholinergic receptors are located in the postsynaptic membrane of effector organ cells at the endings of postganglionic cholinergic (parasympathetic) fibers, as well as in the central nervous system (cortex, reticular formation).
H-cholinergic receptors are located in the postsynaptic membrane of ganglion cells at the endings of all preganglionic fibers (in the sympathetic and parasympathetic ganglia), the adrenal medulla, the sinocarotid zone, the end plates of skeletal muscles and the central nervous system (in the neurohypophysis, Renshaw cells, etc.). Sensitivity to pharmacological substances different H-cholinergic receptors are not the same, which makes it possible to distinguish H-cholinergic receptors of ganglia and H-cholinergic receptors of skeletal muscles.
MECHANISM OF ACTION OF ACETYLCHOLINE
By interacting with cholinergic receptors and changing their conformation, tylcholine changes the permeability of the postsynaptic membrane. With the excitatory effect of acetylcholine, Na ions penetrate into the cell, leading to depolarization of the postsynaptic membrane. This is manifested by a local synaptic potential, which, having reached a certain value, generates an action potential. Local excitation, limited to the synaptic region, spreads throughout the cell membrane (second messenger - cyclic guanosine monophosphate - cGMP).
The action of acetylcholine is very short-lived; it is destroyed (hydrolyzed) by the enzyme acetylcholinesterase.
Medicinal substances can affect the following stages of synaptic transmission:
1) synthesis of acetylcholine;
2) the process of releasing the mediator;
3) interaction of acetylcholine with cholinergic receptors;
4) enzymatic hydrolysis of acetylcholine;
5) capture by presynapric endings of choline formed during the hydrolysis of acetylcholine.
Medicines that stimulate m- and n-cholinergic receptors (m, n - cholinomimetics).
Substances in this group include acetylcholine (AC) and its analogues. It is practically not used as a medicinal product, because It acts very briefly (a few minutes). This group of drugs repeats the effects of the parasympathetic mediator nervous system(PSNS) – AC on organs and systems.
When using m,n-cholinomimetics, the effects of stimulation of m-cholinergic receptors predominate:
Decline intraocular pressure;
Increased secretion of glands of the bronchi, digestive tract, etc.
Increased sweating;
Increased tone and contractile activity of the bronchial muscles,
Increased tone and peristalsis of the gastrointestinal tract,
Decreased heart rate;
Slowing down the speed of excitation through the conduction system of the heart;
Vasodilation (decrease in systemic blood pressure);
Contraction of the muscles of the uterus, bile and Bladder; ureters. The stimulating effect of ACh on n-cholinergic receptors of the autonomic ganglia (sympathetic and parasympathetic) is masked by its m-cholinomimetic effect.
The N-cholinomimetic effect is manifested by blockade of m-cholinergic receptors (for example, atropine): - increase in systemic blood pressure; - facilitation of neuromuscular transmission; - shortness of breath.
CHOLINORESEPTORS
Cholinergic receptors of different cholinergic synapses have unequal sensitivity to the same drugs. In accordance with chemical sensitivity, cholinergic receptors are classified into muscarine-sensitive (M), excited by the fly agaric poison muscarine, and nicotine-sensitive (N), excited by the tobacco alkaloid nicotine, which in turn have several subtypes.
Currently, M-cholinergic receptors are classified into five subtypes: M1, M2, M3, M4, M5. N-cholinergic receptors are classified into two subtypes: Nn- and Nm-cholinergic receptors.
Acetylcholine is a mediator in all cholinergic synapses and stimulates both M- and N-cholinergic receptors.
Types of m-cholinomimetics.
Aceclidine. Pilocarpine (Oftan, Pilocarpin-long, Salajen).
Mechanism of action.
When introduced into the body, aceclidine increases tone and enhances contractions of the intestines, bladder, and uterus. May cause bradycardia, decreased blood pressure, increased salivation, bronchiolospasm.
Aceclidine and pilocarpine have a strong miotic effect. They constrict the pupil, leading to a decrease in intraocular pressure.
Side effects.
With subcutaneous administration of aceclidine in high doses, the following may occur:
salivation, increased sweating, diarrhea.
When applied topically, the following are observed: irritation of the conjunctiva, injection of blood vessels, unpleasant subjective sensations (ache and heaviness in the eye), which go away on their own.
During pilocarpine therapy the following are recorded: headache in the temporal or periorbital areas; Pain in the eyes; myopia, spasm of accommodation, blurred vision, impaired twilight vision; lacrimation, rhinorrhea, follicular conjunctivitis, superficial keratitis, contact dermatitis of the eyelids (rare).
When taken orally, the following are possible: sweating, chills, nausea, vomiting, diarrhea, abdominal pain, dysphagia; change in voice, difficulty breathing; dizziness, asthenia, feeling of a rush of blood to the face; bradycardia, tachycardia, atrioventricular conduction disturbance, hypertension or hypotension, increased blood pressure; increased frequency of urination.
Anticholinesterase substances (not direct cholinomimetics) and cholinesterase reactivators. Classification. Mechanism of action. Pharmacological effects, indications for use. Toxicology of FOS. Symptoms of poisoning, measures to help.
Inactivation of the ACh mediator is carried out mainly by the enzyme acetylcholinesterase (AChE. To facilitate the transmission of excitation, it is necessary to block AChE and slow down the process of ACh hydrolysis. For this purpose, anticholinesterase drugs are used.
reversible and irreversible action
Prozerin - used for glaucoma, myasthenia gravis, peripheral paralysis, atrophy optic nerve, atony of the intestines, bladder.
Classification of cholinomimetics by mechanism of action.
1. M-cholinomimetics (stimulate M-cholinergic receptors): pilocarpine hydrochloride, aceclidine.
2. H-cholinomimetics (stimulate H-cholinergic receptors): cititon, lobeline hydrochloride.
3. M- and N-cholinomimetics (stimulate both M- and N-cholinergic receptors): acetylcholine, carbacholine. +AChE.
Mechanism: reversibly or irreversibly block E cholinesterase, accumulation of ACh in the synaptic cleft, excitation of M-x/r and the muscle subtype H-x/r.
Pharmacodynamics. When they are introduced into the body, the effects associated with the excitation of parasympathetic nerves predominate. As a result of local action on the eye, they lower intraocular pressure, cause miosis, and spasm of accommodation. Thus, due to contraction of the circular muscle of the iris, the pupil narrows (miosis). The outflow of fluid from the anterior chamber is improved by opening the fountain spaces at the base of the iris and Schlemm's canal. Intraocular pressure decreases strongly and for a long time. Contraction of the ciliary muscle of the eye is accompanied by its thickening and movement of the muscle belly closer to the lens. Due to relaxation of the ligament of Zinn, the lens capsule stretches and the lens, due to its elasticity, acquires a more convex shape. The eye is set to close vision (spasm of accommodation).
As a result of the resorptive effect, bronchospasm, bradycardia, hypersalivation, and increased smooth muscle tone are observed. alimentary canal, uterus, gallbladder and bladder.
Indications. Glaucoma, atony of the digestive canal, uterus, bladder, endarteritis.
Contraindications: at bronchial asthma, conduction disorders in the myocardium, with severe organic heart diseases, pregnancy, epilepsy, hyperkinesis, thyrotoxicosis, bradycardia.
Acetylcholine– a drug that stimulates M and N-cholinergic receptors. With systemic action, m-cholinomimetic effects predominate: bradycardia, vasodilation, increased tone and contractile activity of the muscles of the bronchi, gastrointestinal tract, increased secretion of the glands of the bronchi and digestive tract. ACh has a stimulating effect on H-cholinergic receptors in skeletal muscles.
36. M-anticholinergics. Mechanism of action and pharmacological effects of drugs, their Comparative characteristics. Indications for use. Side effects and measures to help.
M-anticholinergics – These are substances that block m-cholinergic receptors. The main effects of m-cholinergic blockers are associated with the fact that they block peripheral m-cholinergic receptors of the membranes of effector cells (at the endings of postganglionic cholinergic fibers), m-cholinergic receptors in the central nervous system (if they penetrate the BBB) and thereby prevent the interaction of the ACh mediator with them.
M-cholinergic blockers reduce or eliminate the effects of irritation of cholinergic (parasympathetic) nerves and the effect of substances with m-cholinomimetic activity (ACh and its analogues, anticholinesterase drugs, as well as mcholinomimetics).
By blocking m-cholinergic receptors, atropine causes:
Antispasmodic effect - decreased muscle tone of the gastrointestinal tract, bile ducts and gallbladder, bronchi, bladder;
Pupil dilation (mydriasis), as a result of a block of m-cholinergic receptors in the circular muscle of the iris;
Increased intraocular pressure, as a result of difficulty in the outflow of fluid from the anterior chamber of the eye (especially with glaucoma);
Paralysis of accommodation, as a result of inhibition of m-cholinergic receptors of the ciliary muscle (m. ciliaris), which leads to its relaxation and tension of the zinc ligament (ciliary band) and a decrease in the curvature of the lens. The eye is set to the far point of vision;
Tachycardia, as a result of decreased cholinergic effects vagus nerve on the heart. Against this background, the tone of the adrenergic (sympathetic) innervation predominates;
Suppression of the secretion of glands (bronchial, nasopharyngeal, digestive, sweat and lacrimal glands). This is manifested by dryness of the oral mucosa, skin, and a change in the timbre of the voice. Decreased sweating can lead to an increase in body temperature.
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