Methods and speed of drug administration. Release of drugs
Routes and methods of administration medicines into the body. Their classification, general and Comparative characteristics. Factors determining the choice of route of administration and dosage form.
The routes of drug administration into the body are divided into enteral and parenteral.
Enteral routes provide access medicinal substances into the body throughout the gastrointestinal tract (enteros - intestinal tube).
Enteral routes include oral, sublingual, subbuccal and rectal routes of drug administration.
1. Oral (oral, ingestion, per os)
The medicine is taken orally through the mouth. Once swallowed, the drug substance is released from the dosage form, dissolves in the contents of the stomach or intestines and is absorbed throughout the gastrointestinal tract, enters the portal vein system, passes through the bloodstream through the liver, then into the inferior vena cava, right heart, pulmonary circulation, left heart, then into the aorta and to the target organs and tissues.
This is the simplest and convenient way introducing drugs into the body. It does not require the assistance of medical personnel and both liquid and solid dosage forms can be administered this way. Provides both systemic and local action. Based on systemic action, drugs that are well absorbed from the stomach or intestines should be prescribed. If it is necessary to create a high concentration of a drug in the gastrointestinal tract, on the contrary, it is advisable to use drugs that are poorly absorbed, which makes it possible to obtain the necessary local effect in the absence of systemic adverse reactions.
The disadvantages of the oral route of administration are: the relatively slow entry of the drug into the general bloodstream, which, in the case of resorptive action, slows down the onset therapeutic effect and does oral route administration of drugs to patients is not acceptable when providing emergency care Ingested medications are subject to a first-pass effect, in which significant amount the drug substance is metabolized in the intestinal wall and in the liver before the substance reaches the systemic circulation, which leads to a decrease in its bioavailability large individual differences in the rate and completeness of absorption the influence of food and other drugs on absorption the impossibility of using based on the systemic effect of drugs that penetrate poorly mucous membrane of the gastrointestinal tract (for example, the anti-tuberculosis antibiotic streptomycin and other antibiotics from the group of aminoglycosides), or destroyed in the gastrointestinal tract (insulin), this method is unacceptable in the absence of consciousness in the patient; some drugs, if orally can cause ulcerative lesions of the gastrointestinal tract
2. Sublingual (under the tongue)
Provides, unlike oral administration, absorption directly into systemic blood flow, bypassing the portal circulation of the liver and first-pass metabolism, which makes it possible to prescribe in this way drugs that are destroyed when taken orally (for example, the b-adrenergic agonist isoprenaline).
Mucous membrane oral cavity has an abundant blood supply, which ensures the rapid entry of medicinal substances into the blood and contributes to the same rapid offensive effect. This makes the sublingual route of administration especially convenient when providing emergency care in outpatient setting, for example, during attacks of angina (taking nitroglycerin) or hypertensive crises (using clonidine or nifedipine).
One of the main disadvantages of the sublingual route of drug administration into the body, which significantly limits its use, is the relatively small absorption area compared to that in the intestine, which allows only highly lipophilic substances with high activity.
The most commonly administered sublingual medications are in the form of solutions, powders and tablets.
3. Subbuccal (behind the cheek)
The medicine is placed between the gums and cheek.
It is a type of drug administration through the oral mucosa, so that it has the same properties as the sublingual route.
It provides a certain advantage over the sublingual method when it is necessary to prolong absorption in order to increase the duration of action, for which special dosage forms are used, for example, in the form of slowly absorbable plates (trinitrolong), which are glued to the gum mucosa. If necessary, unlike oral administration, the effect of the medication can be easily stopped by removing the medication from the mouth.
4. Rectal administration (per rectum)
Administration of the drug through anal hole into the ampulla of the rectum.
Allows you to partially avoid the first pass effect, although not as completely as sublingual administration (the medicine from the middle and lower parts of the rectum enters the general bloodstream, bypassing the liver, from the upper - into the portal bloodstream).
This route of administration can be used for vomiting, esophageal obstruction, decreased portal circulation, in newborns, and when injections are impossible or undesirable.
To the disadvantages rectal route administration of drugs include pronounced individual fluctuations in the speed and completeness of absorption, psychological difficulties and inconvenience of use.
Medicines are administered rectally in the form of rectal suppositories or enemas.
Parenteral routes. The medicine is introduced into the body, bypassing the gastrointestinal tract.
There are injection, inhalation, transdermal routes of administration, as well as local application of drugs.
1. Injection (injections)
The medicine is injected into tissues using a needle and syringe or injected directly into the blood. This overcomes most of the disadvantages of enteral routes of administration: it is possible to introduce substances into the body that are not absorbed or destroyed in the gastrointestinal tract; it ensures that drugs enter the systemic bloodstream, bypassing the liver; they can be performed in patients who are unconscious and inaccessible for contact; in patients with vomiting; medications develop, as a rule, faster and more pronounced (due to faster and more complete absorption), which may have crucial when providing emergency care.
· The disadvantages of injection routes of administration are: the technique is invasive and painful; the assistance of medical personnel is most often required (although self-administration is possible); they require sterility of the administered drugs and adherence to aseptic rules; they are accompanied by tissue damage, and therefore there is a risk of complications associated with this.
Intravenous administration
Aqueous solutions of drugs (less commonly, specially prepared fatty ultraemulsions) are injected into one of the superficial veins in the area of the elbow, hand or foot, and in children - the scalp. If necessary, infusion of large volumes of fluid with high speed injection is carried out into veins of larger diameter, for example, into the subclavian vein.
It ensures direct entry of the drug into the general bloodstream in full (100% bioavailability), which means it ensures high dosing accuracy and promotes the fastest onset of effect.
The main disadvantages of the intravenous route of administration include:
· the impossibility of introducing oil solutions, suspensions, which makes it difficult to use medicinal substances that are poorly soluble in water or precipitate when added to an isotonic sodium chloride solution or glucose solution, usually used as solvents
· Injection requires special skills, so in the vast majority of cases the assistance of trained personnel is required
· in organs with good blood supply, excessively high (toxic) concentrations of medicinal substances may be created in the first minutes after administration
· with the introduction of hypertonic solutions, irritating substances, long-term continuous infusion, the development of thrombophlebitis and venous thrombosis, and in the case of extravasation of certain drugs (calcium chloride solution, strophanthin), the appearance severe irritation tissues and their necrosis.
Intra-arterial administration
Ensures the creation of a high concentration of the drug in the basin of the corresponding artery. Used to administer, for example, thrombolytic drugs, which makes it possible to create them high concentration directly in the area of the existing blood clot and, if not avoided completely, then at least weaken the manifestations of their systemic action, as well as radiocontrast agents (allows for improved visualization of the relevant organs) and drugs that are quickly metabolized (for example, prostaglandins).
It is rarely used for the administration of other drugs, as it is potentially more dangerous than intravenous. This is due to the fact that the introduction of a drug into an artery can provoke a spasm of the vessel, cause thrombosis and thus lead to ischemia and tissue necrosis.
The drug is injected into the muscle tissue of skeletal muscles, such as the gluteus maximus, quadriceps femoris, or deltoid muscles. The muscles are well supplied with blood, which ensures the rapid entry of medicinal substances into the general bloodstream and contributes to the same rapid development effect, but such a sharp initial increase in the concentration of the drug in the blood as with intravenous administration is not observed, and therefore there is no risk of complications associated with this.
Sterile isotonic aqueous and oil solutions and suspensions of medicinal substances. When introducing oil solutions and suspensions, the absorption of medicinal substances slows down, which allows the effect of the drug to be prolonged. For example, a single intramuscular injection of a benzathine-benzylpenicillin suspension ensures that the therapeutic concentration of this antibiotic in the blood is maintained for a month.
Maximum volume intramuscular injection should not exceed 10 ml. If possible, avoid introducing irritating substances into the muscles, as well as hypertonic solutions.
Intramuscular injections, due to the need for deep needle insertion, as a rule, cannot be performed by the patient independently.
Subcutaneous administration
Injections are carried out into loose connective tissue subcutaneous fat most often in the area of the shoulder, thigh or abdomen. Self-injection is possible, since deep penetration of the needle is not necessary.
Due to the relatively poor blood supply, the absorption of drugs is slow and the pharmacological effect, as a rule, develops later than with intramuscular administration. The absorption of drugs and, therefore, the onset of their effect can be accelerated by gently massaging the injection site or applying warm heating pad, causing mild hyperemia. If it is necessary to slow down the absorption and thereby prolong the effect of drugs, use the introduction of their depot forms in the form of oil solutions or suspensions.
Sterile isotonic aqueous and oily solutions and suspensions of drugs in a volume of 1–2 ml are injected under the skin. The drugs administered should not have any effect irritating effect and cause a sharp constriction of blood vessels (such as norepinephrine) due to the threat of inflammation or tissue necrosis at the injection site.
In case of severe violation peripheral circulation, which occurs, for example, in shock, the introduction of drugs under the skin is impractical due to a sharp slowdown in their absorption.
Introduction into the spinal canal
The injection is carried out between the spinous processes, usually of the fourth and fifth lumbar vertebrae. In this case, the medicine can be administered epidurally (into the space between the bone canal of the vertebrae and the dura mater) or subarachnoidally (under the soft tissue). meninges). In this way, it is possible to create a high concentration of drugs, including those that poorly penetrate the BBB, in the cerebrospinal fluid and brain tissue.
The main disadvantages of the method, which significantly limit its use, include quite complex equipment procedures requiring special skills and experience, limiting the amount of injected solution (usually no more than 3 - 4 ml) due to the threat of excessive high promotion intracranial pressure, undesirability reintroduction and the risk of spinal cord injury.
2. Inhalation administration
Drugs are introduced into the body through Airways using special devices or by inhalation in the form of gas mixtures, vapors or aerosols.
This route is the main one for introducing into the body gases (nitrous oxide) and volatile liquids (ether for anesthesia, halothane, enflurane, etc.), used as general anesthetics. It ensures their rapid absorption and development of the effect due to large area surface of the alveoli. Stopping inhalation leads to a rapid cessation of the effect of this type of medicine.
In case of respiratory diseases inhalation route promotes the delivery of drugs directly to target tissues, which makes it possible to reduce the total dose of the drug administered to the body and, therefore, reduce the likelihood of developing side effects associated with their systemic action. In this way, for example, aerosols of bronchodilators, corticosteroids, and some antibiotics are administered. It should be borne in mind that the depth of penetration of a medicinal substance into the respiratory tract depends on the size of the drug particles (particles with an average aerodynamic diameter of more than 5 µm settle predominantly in the pharynx, 2 - 4 µm - in the bronchi, 0.5 - 3 µm - in the alveoli), inhalation technique and inspiratory airflow.
Currently, metered-dose aerosol inhalers (freon-containing or free of freon, as well as breath-activated), powder inhalers (for the administration of powdery substances) and nebulizers (jet and ultrasonic) are used for the inhalation administration of aerosols.
When using most metered dose aerosol inhalers containing propellant gas, bronchial tree no more than 20 - 30% of the administered dose of the medicinal substance is received. The rest of the drug settles in the mouth and pharynx, then is swallowed and absorbed, thus determining the development of systemic effects. Powder inhalers allow you to increase the fraction of the drug reaching the lower respiratory tract by up to 30 - 50%. Optimal ratio of local and systemic effects is achieved by using nebulizers, in which an aerosol is created by passing a powerful stream of air or oxygen under pressure through a drug solution, or using ultrasound. This creates a suspension of tiny particles of the drug, which the patient inhales through a mouthpiece or face mask. The respirable fraction of drugs administered using metered aerosol inhalers can be increased if they are used with spacers. A spacer is a special chamber placed on the head of the inhaler dosing device. Allows you to increase the distance between the inhaler and the patient's mouth. As a result, the drug particles have time to lose excessive speed, the propellant gas partially evaporates and the impact of the aerosol jet on back wall throats.
3. Transdermal administration. The transdermal route involves application of the drug to the skin to provide systemic action. For this purpose, ointments, patches, gels are used, as well as recently developed special dosage forms that ensure the release of the drug at a given speed, the so-called transdermal therapeutic systems(TTS/TTS).
Preferanskaya Nina Germanovna
Associate Professor, Department of Pharmacology, Faculty of Pharmacy First Moscow State Medical University them. THEM. Sechenova, Ph.D.
Magnesium sulfate, taken orally by an adult at a dose of 10-30 g in ½ glass of water, is poorly absorbed (no more than 20%), causes fluid retention, increases osmotic pressure in the gastrointestinal tract, enhances intestinal motility and has a laxative effect. And taken orally (on an empty stomach) 20-25% solution of magnesium sulfate, 1 tbsp. spoon 3 times a day irritates nerve endings mucous membrane of the duodenum, increases the secretion of cholecystokinin and gives a choleretic effect. When administered parenterally, magnesium sulfate exhibits a calming effect on the central nervous system, and depending on the dose administered, it has a sedative, hypnotic, and narcotic effect. IN large doses it has a depressant effect on neuromuscular transmission and may exhibit anticonvulsant, curare-like action. Magnesium sulfate reduces the excitability of the respiratory center and in large doses can easily cause respiratory paralysis. With intravenous (slow) or intramuscular injection of 5-20 ml of 20 or 25% magnesium sulfate solution, hypotensive effect, which is associated with the presence of myotropic antispasmodic properties and a calming effect. Along with this, the drug reduces the symptoms of angina pectoris and is used to relieve arrhythmias ( ventricular tachycardia and arrhythmias associated with an overdose of cardiac glycosides). It is used for pain relief during childbirth, for colic, urinary retention and other indications.
The route of administration has big influence on the duration of the drug. With enteral routes of administration, the onset of action (latent period) and duration of action of the drug increases compared to parenteral (inhalation and injection) routes. The strength of the drug also depends on the route of administration. When the same dose of the active substance is introduced into the body, the effectiveness of the pharmacological therapeutic action the drug will be 5-10 times more when administered intravenously than when administered orally.
All routes of drug administration into the human body are divided into two main groups: enteral(through the digestive tract) and parenteral(bypassing gastrointestinal tract).
TO enteral routes include the administration of drugs:
- inside ( oral - per os);
- sublingually (sub lingua);
- buccal (buccal);
- rectally (per rectum).
Parenteral routes introductions are divided into:
- injection;
- intracavitary;
- inhalation;
- transdermal (cutaneous).
There is a less common classification of routes of administration:
- routes of administration that violate the integrity of the skin (injections, infusions);
- routes of administration without violating the integrity of the integument, this includes all enteral routes, inhalation, cutaneous and introduction into natural body cavities (for example, into the ear, eye, nose, urethra, wound pockets).
ENTERAL ROUTE OF DRUG ADMINISTRATION
The most common, convenient and simple way of introducing drugs into the body is oral administration(orally, per os ) . Various dosage forms can be administered internally: solid(tablets, powders) and liquid(infusions, decoctions, solutions, etc.). This method of administration is natural, because in the same way we introduce food into the body. This route of administration does not require sterilization, special training sick or medical personnel. Absorption of the drug by oral administration occurs over a large area (more than 120 m2), which, with intensive blood circulation, allows the active substances to be quickly absorbed (15-20 minutes) and provide the necessary pharmacological effect. Oral administration is especially convenient for long-term treatment chronic patients. When treating patients with drugs taken orally, it is very important to prevent possible destruction and their modification in the stomach or intestines. Many drugs are coated with enteric coatings to avoid contact with aggressive hydrochloric acid of the stomach. Medicinal substances (DS) different structure and origin interact with many components found in the gastrointestinal tract, including digestive enzymes and food. Therefore, it is important to know what changes, when administered orally, the medicine undergoes under the influence of food itself, digestive juices, and, finally, to have an idea of the influence components food on the absorption of drugs. It is advisable to administer medications 30-40 minutes before. before meals or 1-2 hours after it. Medicines intended to improve digestion - in 15 minutes. or during meals, lipophilic (fat-soluble) drugs - after meals. It is better to take medications with ½ or 1/3 glass of boiled or filtered water.
Some drugs are introduced into the body to obtain a very rapid therapeutic effect. sublingually(under the tongue). The mucous membrane of the oral cavity has an abundant blood supply, so the medicine is quickly and well absorbed, the effect occurs within 1-2 minutes. In this case, the drug is released and absorbed into the superior vena cava system, entering the general bloodstream, bypassing the gastrointestinal tract and liver. Can be administered sublingually easily soluble tablets, solutions, drops(on a piece of sugar), keep them in the mouth until completely absorbed (about 15 minutes). Currently, many antiseptic drugs are available in the form chewable tablets, lozenges, for example, Septolete, Lizobakt, Laripront, etc. To relieve attacks of angina pectoris, Validol and Nitroglycerin are administered sublingually. The painkiller Buprenorphine is available in sublingual tablets under the TN “Ednok”. The disadvantage of this route of administration is the small absorption surface of the oral mucosa, the irritating effect of drugs or their unpleasant taste.
With the advent of new innovative dosage forms it became possible to use drugs buccal(cheek), which ensures their prolonged effect and constant concentration in the blood. Absorbable films, cheek patches or buccal tablets, appliqués contain lipophilic non-polar substances, are well absorbed through the buccal muscles by passive diffusion. When Sustabukkal is administered, its effect appears within 3-5 minutes. and continues until 6 hours. Other examples are buccal mucoadhesive turbutalin sulfate patch, buccal tablets Gramicidin C, Loracept, etc.
IN medical practice Drugs are often administered rectally(through the rectum). Absorbed in the lower part of the rectum, the drug enters the lower hemorrhoidal veins and then into the general bloodstream, bypassing the liver. This is especially important when prescribing drugs that are destroyed in the liver. With the correct shallow injection, after which the patient can lie down on his side for a while, absorption occurs evenly and completely. The rectal route of administration ensures maximum bioavailability and rapid pharmacological effect of the drug. However, it must be remembered that deep injection is accompanied by the drug entering the superior hemorrhoidal vein and then along the portal vein to the liver. This medicine undergoes a first pass through the liver (presystemic metabolism), partially producing inactive metabolites and reducing its bioavailability. Used to administer drugs rectally suppositories And microenemas. This method is promising and the most convenient compared to oral administration when prescribing medications to young children and the elderly. He found the most wide application in pediatric, gerontological and proctological practice, for various diseases of the lower sections digestive tract(hemorrhoids, fissures anus, spastic colitis, chronic constipation). For direct effects on the rectal mucosa and adrectal tissue, drugs are administered V rectal suppositories , which provides the necessary local effect.
The disadvantages of the rectal route of administration include the inconvenience of administration, especially if the medicine must be administered at work, on a train, on an airplane or other in public places, because it requires a special individual environment. To reduce pronounced individual fluctuations in the rate and completeness of drug absorption, it is advisable to administer it after a cleansing enema or spontaneous bowel movement. It must be taken into account that the rectum does not produce digestive enzymes, therefore, high-molecular medicinal substances of protein, fat and polysaccharide structure will be poorly absorbed in it.
Continued in MA 11/12
Pharmacokinetics
Pharmacokinetics is a section of general pharmacology that studies the processes of absorption, distribution, metabolism and excretion of drugs (i.e., this is how the body acts on a drug).
Routes of administration of drugs into the body
Medicinal substances are introduced into the human body in various ways. The practitioner is given full right introduce medicine into the body by any known route.
The choice of method of administration is dictated by the following three circumstances:
Condition of the patient: severity of the disease (in cases threatening patient's life, fast-acting substances are introduced).
Properties of drugs (solubility, speed of development of effect, duration of action of drugs).
Intuition, vocational training doctor
Traditionally, enteral and parenteral routes of drug administration into the body are distinguished.
Enteral routes of administration(via the gastrointestinal tract):
oral (through the mouth);
sublingual (under the tongue);
buccal (“sticking” to the mucous membrane of the cheek, gum);
duodenal (into the duodenum);
rectal (into the rectum).
Parenteral routes of administration(i.e. bypassing the gastrointestinal tract):
subcutaneous;
intradermal;
intramuscular;
intravenous;
intra-arterial;
intraosseous;
subarachnoid;
transdermal;
inhalation
Enteral routes of drug administration
Oral(lat. peros) - the most common method of administration. About 60% of all drugs are prescribed orally. For oral administration, various dosage forms are used: tablets, powders, capsules, solutions, etc. When taken orally, the drug goes through the following stages:
Oral cavity → esophagus → stomach → small intestine → large intestine → rectum.
Absorption of a number of substances occurs partially from the stomach (weak electrolytes that are acidic in nature - aspirin, barbiturates, etc.). But the vast majority of drugs are absorbed mainly in the small intestine (this is facilitated by intensive blood supply and a large absorption surface - ≈ 120 m2). Absorption of the drug when taken orally begins within 15–30 minutes.
After absorption in the intestine, the drug goes through the following stages:
Small intestine → absorption → portal vein → liver (partially destroyed) → inferior vena cava → big circle blood circulation → organs and tissues (therapeutic effect).
Advantages of the method:
simplicity and convenience;
naturalness;
relative safety;
no sterility or hands of medical personnel required.
Disadvantages of this method:
slow onset of effect;
low bioavailability;
individual differences in the speed and completeness of absorption;
the effect of food and other substances on absorption;
the impossibility of using drugs that poorly penetrate the mucous membrane of the gastrointestinal tract (streptomycin) and are destroyed in the gastrointestinal tract (insulin, pregnin);
inability to use in case of vomiting and coma.
Sublingual(lat. sublingua). The mucous membrane of the oral cavity has an abundant blood supply, and substances absorbed through it quickly enter the blood. The effect of sublingual administration occurs by the end of the first minute. Route of medicinal substances:
Oral cavity → superior vena cava system → right parts of the heart → pulmonary circulation → left heart → aorta → organs and tissues (therapeutic effect).
This method is used to administer some fast-acting vasodilators (nitroglycerin, validol), steroid hormones and their derivatives (methyltestosterone, pregnin), gonadotropin and other drugs that are poorly absorbed or inactivated in the gastrointestinal tract.
Advantages of the sublingual route of administration:
drugs are not affected gastric juice;
do not pass through the liver.
Disadvantage: inability to use medications with bad taste and with an irritating effect on the oral mucosa.
Buccal Polymer films (trinitrolong) are used, which are “glued” to the mucous membrane of the cheek or gum. Under the influence of saliva, the films melt, the pharmacologically active substance (nitroglycerin in trinitrolong) is released and a therapeutic concentration is created in the systemic circulation for a certain time.
Duodenal route of administration . A probe is inserted through the esophagus into the duodenum and a liquid is injected through it (for example, magnesium sulfate as a choleretic agent). This makes it possible to quickly create a high concentration of the drug in the intestines. The advantage is that the medicine is not exposed to gastric juice. But this route of administration is technically complex and is rarely used.
Rectally(lat. perrectum) medicinal substances are prescribed in the form of suppositories, solutions in enemas (V- no more than 50–100 ml + the solution must be heated to 37–38 º C, since otherwise a reflex to emptying may occur). The therapeutic effect with this route of administration develops within 5–15 minutes. Drug route:
Rectum → inferior and middle hemorrhoidal veins (about 50% of the drug substance) → inferior vena cava → systemic circulation → organs and tissues (therapeutic effect).
Part of the drug is absorbed through the superior hemorrhoidal vein and enters the liver through the portal vein, where it is partially metabolized.
Advantages of the rectal route of administration:
the medicinal substance is not exposed to the juices of the digestive tract;
does not irritate the gastric mucosa;
the drug substance bypasses the liver (about 50%);
can be used when vomiting, in an unconscious state.
Disadvantages of this method:
inconvenience, unhygienic;
individual differences in the speed and completeness of absorption.
Medicines can be administered naturally(inhalation, enteral, cutaneous) and using technical means. In the first case of transporting them to internal environments The body is provided with the physiological absorption ability of the mucous membrane and skin, in the second it occurs by force.
It is rational to divide the routes of drug administration into enteral, parenteral and inhalation.
Enteral gilah involves the administration of drugs through various departments digestive canal. With sublingual (administration of medications under the tongue) and subbuccal (administration of medications on the buccal mucosa) routes of administration, absorption begins quite quickly, the drugs exhibit general action, bypass the liver barrier, do not come into contact with hydrochloric acid of the stomach and enzymes of the gastrointestinal tract. Sublingually prescribed fast-acting drugs with high activity (nitroglycerin), the dose of which is quite small, as well as drugs that are poorly absorbed or destroyed in the digestive canal. The drug should be in the oral cavity until completely absorbed. Swallowing it with saliva reduces the benefits of this route of administration. Frequent use Sublingual medications may cause irritation of the oral mucosa.
The oral route of administration involves swallowing the drug and then passing it through the digestive canal. This method is the simplest and most convenient for the patient; it does not require sterile conditions. However, only a small part of the drugs begins to be absorbed in the stomach. For most drugs, a slightly alkaline environment is favorable for absorption small intestine, so when oral administration the pharmacological effect occurs only after 35-45 minutes.
Medicines taken orally are exposed to digestive juices and may lose their activity. An example would be the destruction of insulin and other protein drugs by proteolytic enzymes. Some drugs are exposed to the hydrochloric acid of the stomach and the alkaline contents of the intestines. In addition, substances that are absorbed from the stomach and intestines enter through the portal vein system into the liver, where they begin to be inactivated by enzymes. This process is called the first pass effect. This is why, and not because of poor absorption, the doses of some drugs ( narcotic analgesics, calcium antagonists) when administered orally should be significantly greater than when administered into a vein. The biotransformation of a substance during its initial passage through the liver is called systemic metabolism. Its intensity depends on the speed of blood circulation in the liver. It is recommended to take medications orally 30 minutes before meals.
Medicines are administered orally in the form of solutions, powders, tablets, capsules, and granules. To prevent the destruction of certain medicinal substances in the acidic environment of the stomach, tablets are used that are coated with a coating that is resistant to the action of gastric juice, but soluble in the alkaline environment of the intestine. There are dosage forms (multilayer-coated tablets, capsules, etc.) that provide gradual absorption of the active substance, which allows the therapeutic effect of the drug to be prolonged (retarded forms of drugs).
It should be remembered that in patients (especially the elderly) with impaired esophageal peristalsis or in those who have been in the horizontal position, tablets and capsules can linger in the esophagus, forming ulcers in it. To prevent this complication, it is recommended to take tablets and capsules with big amount water (at least 200 ml). Reducing the irritating effect of drugs on the gastric mucosa can be achieved by preparing them in the form of mixtures with the addition of mucus. In case of significant irritant (or ulcerogenic) effect of drugs, especially those that require long-term course application(for example, diclofenac sodium) it is advisable to take after meals.
Administration of medications by mouth is impossible or difficult during vomiting, during convulsions, or in a state of fainting.
Sometimes drugs are administered duodenally (through a tube into the duodenum), which makes it possible to quickly create a high concentration of the substance in the intestine. Thus, for example, magnesium sulfate is administered (to achieve a choleretic effect or with diagnostic purpose).
Medicines are administered rectally (into the rectum) in the form of suppositories (candles) or enemas (for adults - no more than 50-100 ml in volume). Rectal administration avoids the irritating effect of substances on the gastric mucosa, and also makes it possible to use them in cases where oral administration is difficult or impossible (nausea, vomiting, spasm or esophageal obstruction). Absorbed from the lumen of the rectum, drugs enter the bloodstream not through portal vein, but by the system of the inferior vena cava, thus bypassing the liver. Therefore, the strength of the pharmacological action of drugs and the accuracy of dosage for rectal administration are higher than for oral administration, which makes it possible to administer drugs not only preferentially local action(microanesthetic, anti-inflammatory, disinfectant), but also general action (hypnotics, analgesics, antibiotics, cardiac glycosides, etc.).
Parenteral route (bypassing the digestive canal). All types of parenteral administration pursue the same goal - to deliver faster and without loss active substance the drug into the internal environment of the body or directly into the pathological focus.
Inhalation is the most physiological of natural ways administration of medicinal substances. In the form of aerosols, substances are prescribed primarily to obtain local effect(at bronchial asthma, inflammatory processes of the respiratory tract), although most substances (adrenaline, menthol, most antibiotics) administered in this way are absorbed and also have a resorptive (general) effect. Inhalation of gaseous or dispersed solid and liquid drugs (aerosols) ensures their entry into the blood almost as quickly as injection into a vein, is not accompanied by injury from an injection needle, and is important for children, the elderly and debilitated patients. The effect is easy to control by changing the concentration of the substance in the inhaled air. The rate of absorption depends on the volume of respiration, the active surface area of the alveoli, their permeability, the solubility of substances in lipids, the ionization of drug molecules, the intensity of blood circulation, etc.
To facilitate inhalation use non-volatile solutions, use special sprayers (inhalers), and the introduction and dosing of gaseous substances (nitrous oxide) and volatile liquids (ether for anesthesia) is carried out using machines (anesthesia) artificial ventilation lungs.
Cutaneous route widely used in dermatology to directly affect pathological process. Some substances are highly lipophilic, can partially penetrate the skin, be absorbed into the blood and have a general effect. Rubbing ointments and liniments into the skin promotes deeper penetration of medicinal substances and their absorption into the blood. With ointment bases lanolin, spermaceti and pork fat provide deeper penetration of medicinal substances into the skin than petroleum jelly, since they are closer in composition to body lipids.
Recently, special pharmacotherapeutic systems have been developed for transcutaneous delivery of a drug (for example, nitroglycerin) into the systemic circulation. These are special dosage forms that are fixed with an adhesive substance on the skin and ensure slow absorption of the drug, thereby prolonging its effects.
Introduction of medicinal substances into the conjunctival sac, external ear canal, into the nasal cavity most often suggests local impact on the pathological process in the relevant organs (conjunctivitis, otitis media, rhinitis). Some drugs for local application tend to exhibit a resorptive effect (for example, m-anticholinergics and anticholinesterase drugs with glaucoma).
The introduction of medicinal substances into body cavities is rarely used. Antibiotics are usually administered into the abdominal cavity during surgical operations. Introduction into the cavities of the joints and pleura is advisable for eliminating inflammatory processes(arthritis, pleurisy).
Among the parenteral routes of drug administration, injection is common: into the skin, subcutaneously, into a muscle, into a vein, into an artery, subarachnoid, subdural, suboccipital, intraosseous, etc.
Injection into the skin is used primarily for diagnostic purposes (for example, a test for increased individual sensitivity to antibiotics and local anesthetics), as well as for vaccination.
Often drugs are administered subcutaneously and intramuscularly. These methods are used when it is impossible to administer substances by mouth or into a vein, as well as to prolong the PHARMACOTHERAPEUTIC effect. Slow absorption of the drug (especially oil solutions) allows you to create a depot in the subcutaneous tissue or muscles, from which it gradually enters the blood and is there in the required concentration. Substances that have a significant local effect should not be injected under the skin or into the muscle, as this can lead to inflammatory reactions, formation of infiltrates and even necrosis.
Administration into a vein saves the time required for the absorption of medications through other routes of administration, makes it possible to quickly create their maximum concentration in the body and obtain a clear therapeutic effect, which is very important in cases of emergency care.
Only aqueous sterile solutions of drugs are injected into the vein; the introduction of suspensions and oil solutions is strictly prohibited (to prevent vascular embolism, vital important organs), as well as substances that cause intense blood thickening and hemolysis (gramicidin).
Medicines can be injected into a vein quickly, slowly in a stream or slowly in a drip. It is often administered slowly (especially to children), since many drugs tend to cause the effect too quickly (strophantine, ganglion blockers, plasma replacement fluids, etc.), which is not always desirable and can be life-threatening. Rational is drip introduction solutions, usually start with 10-15 drops per minute. and gradually increase the speed; the maximum rate of administration is 80-100 drops per 1 minute.
The medication, which is injected into a vein, is dissolved in an isotonic solution (0.9%) NaCl or 5% glucose solution. Breeding in hypertonic solutions(for example, 40% glucose solution), except in isolated cases, is less advisable due to possible damage to the vascular endothelium.
Recently, they have been using rapid (within 3-5 minutes) administration of drugs into a vein in the form of a bolus (Greek. Bolos - com). The dose is determined in milligrams of the drug or in milliliters of a certain concentration of the substance in solution.
Introduction into an artery allows you to create a high concentration of the drug in the area of the blood supply to this artery. This way is sometimes administered antitumor agents. To reduce their total toxic effect the flow of blood may be artificially slowed down (compression of the veins). They also inject into the artery radiocontrast agents to clarify the location of a tumor, thrombus, aneurysm, etc.
Medicines that do not penetrate well through the blood-brain barrier can be administered under the membranes of the brain - subarachnoid, subdural, suboccipital. For example, some antibiotics are used in cases infection tissues and membranes of the brain.
Intraosseous injections are used if it is technically impossible to administer into a vein (children, elderly people), and also sometimes for injection large quantity plasma-substituting fluids (into the spongy substance of the heel bone).
Advantages of parenteral routes of drug administration:
1. Pharmacological effect develops quickly (magnesium sulfate reduces arterial pressure during hypertensive crisis).
2. High dosing accuracy (mg/kg body weight can be calculated).
3. The possibility of administering drugs that are destroyed by the enteral route (insulin, heparin).
4. The medicine can be administered to patients in an unconscious state (insulin for diabetic coma).
Disadvantages of parenteral routes of drug administration:
1. The drug must be sterile.
2. You need equipment and the skills of medical personnel.
3. Danger of infection.
4. Injection of medications often causes pain.
Electrophoresis is often called bloodless injection. Anions and cations of ionized drugs are able, under the influence of an electric field, to penetrate into the body through intact skin (ducts of sweat and sebaceous glands) and mucous membrane. They are partially retained in tissues, bind to proteins of cells and intercellular fluid, and partially are absorbed further and enter the general bloodstream.
Pharmacology: lecture notes Valeria Nikolaevna Malevannaya
2. Routes of administration of medicinal substances
There are enteral and parenteral route administration of medicinal substances. Enteral route– administration of the drug orally through the mouth ( per os), or orally; under the tongue ( sub lingua), or sublingually; into the rectum ( per rectum), or rectally.
Taking the drug by mouth. Advantages: ease of use; comparative safety, absence of complications inherent in parenteral administration.
Disadvantages: slow development of therapeutic action, the presence of individual differences in the speed and completeness of absorption, the influence of food and other drugs on absorption, destruction in the lumen of the stomach and intestines (insulin, oxytocin) or when passing through the liver.
Medicines are taken orally in the form of solutions, powders, tablets, capsules and pills.
Application under the tongue (sublingual). The medicine enters the systemic circulation, bypassing the gastrointestinal tract and liver, beginning to act after a short time.
Introduction into the rectum (rectal). A higher concentration of drugs is created than with oral administration.
Suppositories (suppositories) and liquids are administered using enemas. Disadvantages of this method: fluctuations in the speed and completeness of absorption of drugs, characteristic of each individual, inconvenience of use, psychological difficulties.
Parenteral route- This different kinds injections; inhalation; electrophoresis; superficial application of drugs to the skin and mucous membranes.
Intravenous administration (IV). Medicines are administered in the form of aqueous solutions.
Advantages: rapid entry into the blood; if a side effect occurs, it is possible to quickly stop the effect; the possibility of using substances that are destroyed and not absorbed from the gastrointestinal tract. Disadvantages: with long-term intravenous administration along the vein, pain and vascular thrombosis may occur, as well as the risk of infection with hepatitis B viruses and human immunodeficiency.
Intra-arterial administration (i.a.). It is used in cases of diseases of certain organs (liver, blood vessels of the limb), creating a high concentration of the drug only in the corresponding organ.
Intramuscular administration (IM). Aqueous, oily solutions and suspensions of medicinal substances are administered. The therapeutic effect occurs within 10–30 minutes. The volume of the administered substance should not exceed 10 ml.
Disadvantages: the possibility of the formation of local soreness and even abscesses, the danger of accidentally getting the needle into a blood vessel.
Subcutaneous administration. Aqueous and oil solutions are introduced. Solutions of irritating substances that can cause tissue necrosis should not be injected subcutaneously.
Inhalation. Gases (volatile anesthetics), powders (sodium cromoglycate), and aerosols are administered in this way. By inhaling the aerosol, a high concentration of the drug substance is achieved in the bronchi with minimal systemic effect.
Intrathecal administration. The medicine is injected directly into the subarachnoid space. Application: spinal anesthesia or the need to create a high concentration of a substance directly in the central nervous system.
Local application. For getting local effect Medicines are applied to the surface of the skin or mucous membranes.
Electrophoresis is based on the transfer of medicinal substances from the surface of the skin to deep-lying tissues using galvanic current.
From the book Handbook of Nursing author Aishat Kizirovna Dzhambekova From book Latin language for doctors author A. I. Shtun From the book Pharmacology: lecture notes authorSection 3 Use of medicinal substances Rules for prescribing, storing and distributing medicinal products In the successful treatment of patients, it is necessary to follow correct dosage and intervals between the administration of drugs. Prescription of drugs is carried out daily by the senior
From the book Latin for Doctors: Lecture Notes author A. I. ShtunMethods of administering medicinal substances You can apply the medicine externally through skin and mucous membranes, by inhalation through the respiratory tract, orally through the mouth or rectum and by injection (parenteral) intradermally, subcutaneously, intramuscularly,
From the book Pharmacology author Valeria Nikolaevna Malevannaya35. Trivial names of medicinal substances Some chemical compounds, used as medicinal substances, retain the same traditional semi-systematic names that they received in chemical nomenclature ( salicylic acid,
From the book Bronchial asthma. Available about health author Pavel Alexandrovich Fadeev1. Types of action of medicinal substances Pharmacodynamics deals with the study of the effect that medicinal substances have on the body. The action of a substance at the site of its administration before absorption into the general bloodstream is called local action, and the reaction
From book Pocket Guide vital medicines author author unknown5. Absorption and distribution of medicinal substances Absorption of a medicinal substance is the process of its entry from the site of administration into the bloodstream, depending not only on the route of administration, but also on the solubility of the medicinal substance in tissues, speed
From the book Eco-Friendly Food: Natural, Natural, Living! by Lyubava Live7. Side effects of drugs the following types side effects and complications caused by drugs: 1) side effects related to the pharmacological activity of drugs;2) toxic complications, conditioned
From the book Directory of Essential Medicines author Elena Yurievna Khramova1. Trivial names of medicinal substances Some chemical compounds used as medicinal substances retain the same traditional semi-systematic names that they received in chemical nomenclature (salicylic acid,
From the author's book5. Routes of administration of medicinal substances There are enteral and parenteral routes of administration of medicinal substances. Enteral route - administration of the drug orally through the mouth (peros), or orally; under the tongue (sub lingua), or sublingually; into the rectum (per rectum), or
From the author's book6. Mechanism of action of drugs, doses of drugs The basis of the action of most drugs is the process of influencing physiological systems organism, expressed by changes in the rate of flow natural processes. Possible
From the author's bookRoutes of drug administration exist various ways delivery of medications to the affected organ: through the gastrointestinal tract (taking pills, etc.), intravenously, intramuscularly, etc. For bronchial asthma in the best possible way
From the author's bookChapter 1. Routes of administration, doses, rules for taking medicines Methods and routes of administration of medicines What happens to the medicine in the body? Why are so many dosage forms needed? Why can’t everything be released in tablet form or, for example,
From the author's bookMethods and routes of drug administration What happens to the drug in the body? Why are so many dosage forms needed? Why can’t everything be produced in the form of tablets or, for example, syrups? This section is dedicated to answering these questions.
From the author's bookEntry routes toxic substances into the human body There are three main ways toxins enter the human body:? orally (through the mouth);? inhalation (through the respiratory system);? cutaneously (through
From the author's bookRoutes of administration Most brief classification divides everything medications depending on the route of their administration: enteral and parenteral, i.e. administered through the gastrointestinal tract or by injection, respectively. There are several main
