The main forms and methods of drug administration. Ways of introducing drugs into the body

Pharmacokinetics

Pharmacokinetics - a section of general pharmacology that studies the processes of absorption, distribution, metabolism and excretion of drugs (that is, this is how the body acts on the drug).

Routes of administration medicines into the body

Medicinal substances are introduced into the human body in various ways. The practitioner is given full right inject the drug into the body by any known route.

The choice of the method of administration is dictated by the following three circumstances:

The patient's condition: the severity of the disease (in cases threatening patient's life, fast-acting substances are introduced).

Drug properties (solubility, rate of effect development, duration of drug action).

Intuition, professional training of a doctor.

Traditionally, enteral and parenteral routes of administration of drugs into the body are distinguished.

Enteral routes of administration(through the gastrointestinal tract):

oral (by mouth);

sublingual (under the tongue);

buccal (“gluing” to the buccal mucosa, gums);

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 administered orally. For oral administration, various dosage forms are used: tablets, powders, capsules, solutions, etc. When taken through the mouth, the drug goes through the following steps:

Oral cavity → esophagus → stomach → small intestine → large intestine → rectum.

The 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 small intestine(this is facilitated by intensive blood supply and a large suction surface - ≈ 120 m 2). Absorption of drugs at oral intake starts in 15-30 minutes.

After absorption in the intestine, the drug goes through the following steps:

Small intestine → absorption → portal vein → liver (partially destroyed) → inferior vena cava → systemic circulation → organs and tissues (therapeutic effect).

Advantages of the method:

simplicity and convenience;

naturalness;

relative safety;

sterility, hands of medical staff is not required.

The disadvantages of the method:

slow onset of effect;

low bioavailability;

individual differences in the speed and completeness of absorption;

influence of food and other substances on absorption;

the impossibility of using drugs that do not penetrate well through the mucosa of the gastrointestinal tract (streptomycin), which are destroyed in the gastrointestinal tract (insulin, pregnin);

inability to use with 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 bloodstream. The effect of sublingual administration occurs by the end of the first minute. Pathway of medicinal substances:

Oral cavity → superior vena cava system → right heart → pulmonary circulation → left heart→ aorta → organs and tissues (therapeutic effect).

In this way, some vasodilators fast-acting (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 exposed to the action of gastric juice;

do not pass through the liver.

Disadvantage: the impossibility of using drugs with an unpleasant taste and with an irritating effect on the oral mucosa.

buccal polymer films (trinitrolong) are used, which are “glued” to the buccal mucosa or gums. Under the influence of saliva, the films melt, release the pharmacologically active substance (nitroglycerin in trinitrolong) and create a therapeutic concentration in the systemic circulation for a certain time.

Duodenal route of administration . The probe is inserted through the esophagus into the duodenum and a liquid is injected through it (for example, magnesium sulfate as a choleretic). This makes it possible to quickly create a high concentration of the drug in the intestine. Advantage - the medicine is not exposed to the action of gastric juice. But this route of administration is technically complex and 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, otherwise a reflex to emptying may occur). Therapeutic effect with this route of administration, it develops in 5-15 minutes. The drug route:

Rectum → lower and middle hemorrhoidal veins (about 50% of the medicinal substance) → inferior vena cava → systemic circulation → organs and tissues (therapeutic effect).

Part of the drug is absorbed through the superior hemorrhoidal vein and portal vein enters the liver, 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 medicinal substance bypasses the liver (about 50%);

can be used for vomiting, in an unconscious state.

The disadvantages of the method:

inconvenience, unhygienic;

individual differences in the speed and completeness of absorption.

Routes of drug administration

Depending on the properties and purposes of use, medicinal substances can be introduced into the body. different ways. The latter are divided into enteral i.e. using the gastrointestinal tract (oral, sublingual, rectal) and parenteral when the drug is administered in any way, bypassing gastrointestinal tract. It is advisable to divide the latter ways into injection - with violation of the skin (subcutaneous, intramuscular, intravenous, subarachnoid, intraarterial, intracardiac) and others - inhalation, cutaneous, into natural cavities and wound pockets, etc. In medical use, the term "parenteral" has usually a narrower meaning: they designate the most typical and widely used routes of administration - subcutaneous, intramuscular and intravenous.

Enteral routes

oral route. The most natural, simple and convenient for the patient, it does not require sterilization of drugs and specially trained personnel. However, from the point of view of the interests of therapy, especially when providing emergency care, it is not always the best. Sometimes it is simply unacceptable (violation of the act of swallowing, severe or unconscious state of the patient, persistent vomiting, early childhood and so on.). The medicine taken orally meets in the stomach a strongly acidic environment (pH 1.2 - 1.8) and a very active proteolytic enzyme pepsin. It can undergo acid and enzymatic hydrolysis and lose effectiveness. In addition, the absorption of many drugs varies greatly from person to person. different people and even in the same patient. The speed and completeness of absorption also depend on the nature and time of food intake: most vegetables and fruits somewhat reduce the acidity of the juice, dairy products slow down the digestion process in the stomach and the evacuation of food from it, soften irritant effect drugs on the mucosa, can bind some drugs into non-absorbable complexes (for example, tetracycline antibiotics). Resorption of drugs in the intestine also depends on the time of their evacuation from the stomach (it slows down with age and pathology).

Thus, oral medication (with some exceptions such as acetylsalicylic acid and some others with an irritating effect on the gastric mucosa) it is advisable to take 30-40 minutes before meals or 1-2 hours after it. The action of drugs taken orally begins usually after 15-40 minutes. The rate of onset of the effect depends on the nature of the drug and the chosen form, the solubility in water necessary for distribution over the surface of the mucosa, the degree of dispersion of the powder and the disintegration of the tablet. Solutions and fine powders are absorbed faster, tablets, capsules, spansules, emulsions are absorbed more slowly. To speed up the resorption of the drug and reduce irritation of the mucosa, tablets intended for absorption in the stomach are best crushed or dissolved in water beforehand.

Drugs designed for absorption in the intestine (protected by the shell from the effects of acid and pepsin) are resorbed in a slightly alkaline medium (pH 8.0 - 8.5). Fat-soluble drugs are also absorbed from oil solutions (for example, vitamins D, E, A, etc.), but only after the oil has been emulsified by bile acids. Naturally, with violations of the formation and secretion of bile, their resorption will suffer greatly.

After absorption in the stomach and intestines, medicinal substances through the portal vein system enter the liver, where they are partially bound and neutralized. Only after passing through the liver, they enter the general circulation, passing through the phases of distribution, and begin to act. If, moreover, the absorption is slow, the pharmacological effect as a result of the primary passage of the substance through the liver and partial neutralization can be sharply weakened. Therefore, oral dosages of drugs, as a rule, are 2 to 3 times or more higher than doses that are injected under the skin or intramuscularly.

Despite all the shortcomings oral route remains preferable if its use is not precluded by the properties of the drug, the condition of the patient and the purpose of the application. In this case, one should adhere to a simple rule: the medicine should be taken in a sitting or standing position and washed down with ¼ - ⅓ glass of water. If the patient's condition does not allow him to take sitting position, the drug must first be crushed well (if possible - dissolved) and washed down with water in small sips, but in enough. This is necessary in order to avoid the delay of the powder or tablet in the esophagus, to prevent them from sticking to the esophageal mucosa and damaging it.

Medicines	Interaction with food

Tetracyclines, chloramphenicol, ampicillin, sulfonamides, fluoroquinolones, acetylsalicylic acid, indomethacin	Formation of non-absorbable chelate complexes with calcium ions (milk) and iron ions (fruits, vegetables, juices)
Codeine, caffeine, platifillin, papaverine, quinidine and other alkaloids	Formation of non-absorbable complexes with tea and coffee tannins
Levodopa, iron preparations, penicillins, erythromycin, tetracyclines	Decreased bioavailability under the influence of carbohydrates
Ketoconazole	Increased bioavailability under the influence of acidic foods, juices, Coca-Cola, Pepsi-Cola
Spironolactone, lovastatin, griseofulvin, itraconazole, saquinavir, albendazole, mebendazole, drugs fat soluble vitamins	Increased bioavailability under the influence of fats
Nialamide	Development of a toxic reaction ("cheese crisis", tyramine syndrome) when taken together with foods rich in tyramine (avocados, bananas, beans, wines, raisins, figs, yogurt, coffee, salmon, smoked herring, smoked meat, liver, beer, sour cream , soy, cheese, chocolate)
Anticoagulants indirect action	Decrease therapeutic action when taken together with foods rich in vitamin K (broccoli, Brussels sprouts and cauliflower, lettuce, zucchini, soy, spinach, walnuts, green tea, liver, vegetable oils)

Examples of drug-food interactions

(ending)

sublingual route. Due to the very rich vascularization of the oral mucosa, the absorption of the drug placed under the tongue, behind the cheek, on the gum, occurs quickly. Naturally, drugs prescribed in this way are not affected by the main digestive enzymes and hydrochloric acid. And finally, resorption is carried out in the system of the superior vena cava, as a result of which the drugs enter the general circulation, bypassing the liver. They act faster and stronger than when taken orally. In this way, some vasodilators are administered, in particular antianginal (nitroglycerin, validol, etc.), when it is necessary to obtain a very quick effect, steroid hormones and their derivatives, gonadotropins and some other agents, the number of which is generally small. Easily soluble tablets, solutions (usually on a piece of sugar), absorbable films (on the gum) are used sublingually. The irritant effect of drugs and bad taste serve as a serious limitation to a wider implementation of this path.

rectal route. The rectal route is used when it is impossible to use drugs inside (vomiting, unconsciousness). From the rectum, 50% of the dose is absorbed into the system of the inferior vena cava, bypassing the liver, 50% enters the portal vein and is partially inactivated in the liver.

Limitations of rectal administration - high sensitivity mucous membrane of the rectum irritants(danger of proctitis), small suction surface, short contact of drugs with the mucous membrane, small volume of solutions for therapeutic enemas (50-100 ml), inconvenience of procedures at work, while traveling.

parenteral routes

In the group of parenteral routes, the most commonly used are subcutaneous, intramuscular and intravenous (table 1). Thanks to rapid offensive effect, these three methods are preferable in emergency care: they are used when prescribing drugs that are not absorbed or destroyed in the gastrointestinal tract (insulin, muscle relaxants, benzylpenicillin, aminoglycosides and a number of other antibiotics, etc.). Means for intravenous anesthesia, painkillers, anticonvulsants, vasodilators and other substances are injected into the vein.

In addition to the obligatory sterility of the drugs themselves and the knowledge of injection techniques, it is necessary to strictly comply with the stricter requirements for the sterilization of syringes, systems for dripping solutions into a vein, or use disposable instruments. The reasons for the tightening are well known: the threat of infection with hepatitis viruses, AIDS, multidrug-resistant strains of microbes.

Table 1

characteristics of subcutaneous, intramuscular and

intravenous routes of drug administration

Index	Route of administration
subcutaneously	intramuscularly	intravenously


Effect onset speed	For most drugs administered in aqueous solutions, after 10 - 15 minutes	Maximum, often at the time of injection

Duration	Less than oral	Less than subcutaneous and intramuscular administration

The strength of the drug	On average, 2 to 3 times higher than with oral administration of the same dose	On average 5 to 10 times higher than oral administration

Sterility of the drug and asepsis of the procedure	Strictly required

End of table 1



Solvent	Water, rarely neutral oil	Water, neutral oil	Water only, in exceptional cases prefabricated ultra-emulsions

Solubility of the drug	Mandatory	Not required, you can enter suspensions	Strictly required

No irritant	Necessarily	Always desirable, otherwise injections are painful, possible aseptic abscesses	It is desirable, sometimes ignored, then the vein is "washed" with warm saline

Isotonicity (isoosmoticity) of the solution	Mandatory, sharply hypo- and hypertonic solutions cause tissue necrosis	Not necessary if small volumes of solution are injected (up to 20 - 40 ml)

subcutaneous route. By administering sterile, isotonic aqueous and oil solutions drugs in a volume of 1 - 2 ml. Solutions have physiological values pH. Preparations should not have an irritating effect (subcutaneous adipose tissue rich in nerve endings) and cause vasospasm. The pharmacological effect occurs 15-20 minutes after the injection. With the introduction under the skin of solutions of an irritating substance calcium chloride and a strong vasoconstrictor norepinephrine necrosis occurs.

This route of administration is commonly used in emergency care at the crash site for the injection of painkillers, vasoconstrictors, psychosedatives, tetanus toxoid etc. This is the usual route for administering insulin. Disposable syringe tubes may be used in disaster medicine. For mass vaccination in a short time, needleless injectors have been created, which, due to high pressure created in the device, allow you to administer the vaccine without breaking the skin. This procedure is very painful.

Medicinal substances are absorbed faster from the subcutaneous tissue of the anterior wall of the abdomen, neck and shoulder. In critical cases, when the intravenous route is already involved or difficult to access (extensive burns), subcutaneous method used to combat dehydration, electrolyte and alkaline-acid imbalances, to parenteral nutrition. Produce long-term drip infusion into subcutaneous tissue(injection sites alternate), the speed of which should correspond to the rate of absorption of the solution. For a day in this way it is possible to enter up to 1.5 - 2 liters of solution. The resorption rate can be significantly increased by adding a hyaluronidase (lidase) preparation to the infused liquid. Solutions (salts, glucose, amino acids) must be isotonic.

intramuscular route. The introduction in this way is less painful than the introduction into the subcutaneous tissue. The most rapidly resorption comes from the deltoid muscle of the shoulder, but more often in practice it is done in the outer upper quadrant of the gluteal muscle (it is more voluminous, which is important for multiple injections). When introducing oily solutions or suspensions, you must first make sure that the needle does not enter the vessel. Otherwise, vascular embolism with severe consequences is possible. Absorption can be accelerated by applying a heating pad or, on the contrary, slowed down with an ice pack.

intravenous route. In this way, the most rapid and complete effect of the medicinal substance on the body is ensured. At the same time, this path requires special responsibility, purely practical skill, caution and knowledge of the properties of the administered drug. Here, in short term maximum (peak) concentrations of the substance are reached in the heart, high - in the central nervous system, only then does it distribute in the body. Therefore, in order to avoid toxic effect injections of poisonous and potent drugs should be done slowly (2 - 4 ml / min), depending on pharmacological properties the drug after preliminary dilution of the ampoule solution (usually 1 - 2 ml) with a solution of sodium chloride or glucose. The presence of air bubbles in the syringe is unacceptable due to life-threatening air embolism. For some drugs, there may be sensitization(that is, they have become allergens for the patient) or genetically determined hypersensitivity (idiosyncrasy). In addition to a preliminary survey of the patient and his relatives, intradermal tests often require the rejection of certain drugs (novocaine, penicillins, etc.). Idiosyncrasy causes lightning-fast development toxic reactions that cannot be predicted. Therefore, injections of substances that are especially dangerous in this regard (iodine-containing radiopaque preparations, quinine, etc.) are carried out in two stages: first, a test dose is administered (no more than 1/10 of the total) and, after making sure that the drug is sufficiently tolerable, the rest is injected after 3-5 minutes quantity.

The introduction of drugs into the vein should be performed by a doctor or under his supervision with constant monitoring of the patient's response. If an infusion system is installed, the administration additional medicines produced through it. Sometimes a permanent (for several days) is used for injections. intravenous catheter, which in the intervals between injections is filled with a weak solution of heparin and plugged with a sterile stopper. For intravenous injections, thin needles are used and blood seepage into tissues is avoided in every possible way, which can lead to irritation and even necrosis of paravenous tissue, inflammation of the vein (phlebitis).

Some substances have an irritating effect on the vein wall. They should first be strongly diluted in an infusion solution (saline, glucose) and administered by drip. For the implementation of intravenous drip infusions, there are special systems disposable, which are equipped with droppers with valves that allow you to adjust the infusion rate (usual - 20 - 60 drops per minute, which corresponds to about 1 - 3 ml / min). For slow introduction of more concentrated solutions into a vein, special devices are sometimes also used - infusers, which allow for a long-term administration of a drug solution at a strictly constant given rate.

intraarterial route. The requirements for drugs administered intra-arterially, into the cavity of the left ventricle of the heart, subarachnoid and into the spongy bone, in general, coincide with those that apply to drugs administered by vein. Use only sterile isotonic aqueous solutions medicines.

The introduction of drugs into the artery is resorted to for special purposes, when it is necessary to create a large concentration of the drug in the tissue or organ supplied by it (for example, an antibiotic, antitumor agent and etc.). It is impossible to achieve similar concentrations of the substance in the organ with other routes of administration due to adverse reactions. Vasodilators are also injected into the artery for frostbite, endarteritis, for the purpose of x-ray examination of regional vessels, and in a number of other cases.

It should be borne in mind that the walls of arteries, unlike venous ones, contain significant amount associated catecholamines (norepinephrine, adrenaline), which, when a substance with irritating properties is administered, can be released and cause persistent vasospasm with necrosis of the supplied tissue. Intra-arterial injections are carried out only by a doctor, usually a surgeon.

Intraosseous path. In terms of the rate of distribution of a substance in the body, this route approaches the intravenous route (the introduction of suspensions, oil solutions, air bubbles is unacceptable). It is sometimes used in traumatology for regional anesthesia of the extremities (the introduction of a local anesthetic into the epiphysis of the bone and the application of a tourniquet above the injection site). This technique is used quite rarely, much more often intraosseous administration of drugs, plasma-substituting fluids and even blood is resorted to involuntarily with extensive burns, including in children (introduction to calcaneus). Puncture of the bone is very painful and requires local anesthesia along the needle. The latter can be left in the bone for repeated injections, for which it is filled with a solution of heparin and closed with a cork.

Intracardiac path. This method of administering drugs (usually adrenaline) is practiced only in one case - during emergency treatment of cardiac arrest. The injection is made into the cavity of the left ventricle and is accompanied by a heart massage. The task - to restore the work of the sinoauricular node that leads the rhythm - is achieved by "pushing" the drug into coronary vessels That's what massage is for.

subarachnoid pathway. It is used to inject local anesthetics or morphine-like analgesics into the spinal canal with a puncture of the meninges ( spinal anesthesia), as well as in the chemotherapy of meningitis - infections that nest in the meninges and are difficult to access for drugs (penicillins, aminoglycosides, etc.) administered in other ways. Injections are usually made at the level of the lower thoracic - upper lumbar vertebrae. The procedure is quite technically delicate and is performed by an experienced anesthetist or surgeon. If the amount of injected solution exceeds 1 ml, the same volume is first released through the needle cerebrospinal fluid. For punctures, it is advisable to use thin needles, since the hole in the dura mater is poorly tightened and liquor oozes into the tissues through it. It causes a change intracranial pressure and severe headaches.

Close to him in technology epidural method drug administration, when a needle is inserted into the spinal canal, but the dura mater is not pierced. In this way for root anesthesia spinal cord solutions of local anesthetics (lidocaine, etc.) are usually injected for reliable anesthesia of organs and tissues below the level of injection into postoperative period and in other cases. A thin catheter can be inserted through the needle into the epidural space, and the infusion of the anesthetic solution is repeated as needed.

All injection methods of drug administration require not only the sterility of drugs and instruments, but also the maximum compliance with all asepsis requirements when performing seemingly even simple procedures.

Preferanskaya Nina Germanovna

Associate Professor, Department of Pharmacology, Faculty of Pharmacy First Moscow State Medical University them. THEM. Sechenov, Ph.D.

Magnesium sulfate, taken by adults orally (orally) 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 annoying nerve endings mucous membrane of the duodenum 12, increases the separation of cholecystokinin and gives a choleretic effect. With parenteral administration of magnesium sulfate, it has a calming effect on the central nervous system, and, depending on the dose administered, a sedative, hypnotic, narcotic effect. IN large doses it has a depressant effect on neuromuscular transmission and may exhibit anticonvulsant, curariform action. Magnesium sulfate reduces excitability 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 associated with the presence of myotropic antispasmodic properties and calming effect. Along with this, the drug reduces the symptoms of angina pectoris and is used to stop arrhythmias ( ventricular tachycardia and arrhythmias associated with an overdose of cardiac glycosides). It is used to anesthetize childbirth, with 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 the duration of action of the drug increase in comparison with 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 pharmacotherapeutic action of the drug will be 5-10 times greater when intravenous method administration than with oral administration.

All ways of introducing drugs into the human body are divided into two main groups: enteral(through the digestive tract) and parenteral(bypassing the gastrointestinal tract).

TO enteral routes include the administration of drugs:

inside ( oral - per os);
sublingually (sub lingua);
transbuccal (cheekly);
rectally (per rectum).

parenteral routes introductions are divided into:

injection;
intracavitary;
inhalation;
transdermal (skin).

There is a less common classification of routes of administration:

routes of administration with violation of the integrity of the skin (injections, infusions);
routes of administration without violating the integrity of the integument, this includes all enteral routes, inhalation, dermal 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 to introduce drugs into the body is ingestion(orally, per os ) . Inside you can enter various dosage forms: solid(tablets, powders) and liquid(infusions, decoctions, solutions, etc.). This method of administration is natural, for in the same way we introduce food into the body. This route of administration does not require sterilization, special training patient or medical personnel. Absorption of the drug when administered orally occurs on large area(more than 120 m 2), which, with intensive blood circulation, makes it possible to quickly be absorbed active substances(15-20 min.) and provide the necessary pharmacological effect. The introduction inside is especially convenient when long-term treatment chronic patients. When treating patients with drugs taken by mouth, it is very important to prevent possible destruction and modifying them in the stomach or intestines. Many drugs are coated with enteric coatings to avoid contact with the aggressive hydrochloric acid of the stomach. Medicinal Substances (PM) different structure and origin interact with a variety of components found in the gastrointestinal tract, including digestive enzymes and food. Therefore, it is important to know what changes the drug undergoes when administered orally under the influence of the food itself, digestive juices, and, finally, to have an idea of the effect constituent parts food for drug absorption. It is advisable to administer drugs 30-40 minutes before. before meals or 1-2 hours after it. Medications designed to improve digestion - in 15 minutes. or during meals, lipophilic (fat-soluble) drugs - after meals. It is better to drink medicines with ½ or 1/3 cup of boiled or filtered water.

Some drugs for getting very fast therapeutic effect injected into the body sublingually(under the tongue). The mucous membrane of the oral cavity has an abundant blood supply, so the drug is quickly and well absorbed, the effect occurs after 1-2 minutes. In this case, the drug is released and absorbed into the system of the superior vena cava, enters the general circulation, bypassing the gastrointestinal tract and liver. Can be administered sublingually easily soluble tablets, solutions, drops(on a piece of sugar), keep them in your 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. Validol, Nitroglycerin are administered sublingually to stop angina attacks. Painkiller Buprenorphine is available in sublingual tablets under the brand name "Ednok". The disadvantage of this route of administration is the small suction 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 LS buccal(cheekly), which ensures their prolonged effect and constant concentration in the blood. Absorbable films, cheek patches or buccal tablets, applications contain lipophilic non-polar substances, are well absorbed through the buccal muscles by passive diffusion. With the introduction of Sustabukkal, its effect is manifested in 3-5 minutes. and continues until 6 o'clock. Other examples are turbutaline sulfate buccal mucoadhesive patch, Gramicidin C buccal tablets, Loracept, etc.

IN medical practice drugs are often injected rectally(through the rectum). Absorbed in the lower part of the rectum, the drug enters the lower hemorrhoidal veins and then into the general circulation, bypassing the liver. This is especially important when prescribing drugs that break down in the liver. With the correct shallow introduction, after which the patient manages to lie down a little on his side, the absorption occurs evenly and completely. Rectal route of administration ensures maximum bioavailability and rapidity pharmacological effect medicines. However, it must be remembered that deep administration is accompanied by the entry of drugs into the superior hemorrhoidal vein and further through the portal vein into the liver. This drug undergoes first pass through the liver (first pass metabolism), inactive metabolites are partially formed and its bioavailability is reduced. Used to administer drugs by the rectal route suppositories And microclysters. This method is promising and most convenient in comparison with oral administration of drugs for young children and the elderly. He found the most wide application in pediatric, gerontological and proctological practice, with various diseases lower divisions digestive tract (hemorrhoids, fissures anus, spastic colitis, chronic constipation). For direct action on the rectal mucosa and pararectal tissue, drugs are administered V rectal suppositories , which provides the desired local effect.

The disadvantages of the rectal route of administration include the inconvenience of administration, especially if the drug must be administered at work, on a train, on an airplane or other in public places, because it requires a special individual setting. To reduce the pronounced individual fluctuations in the rate and completeness of its absorption of the drug, it is desirable to administer it after a cleansing enema or spontaneous bowel movement. It must be borne in mind that the rectum does not produce digestive enzymes, therefore, high-molecular medicinal substances of a protein, fatty and polysaccharide structure will be poorly absorbed in it.

Continued in MA 11/12

Medicines can be introduced into the body in a different way depending on their properties and the purpose of therapy. Route of introduction to to a large extent determines the rate of onset, the duration and strength of drug action, the spectrum and severity of side effects.

There are enteral (through the gastrointestinal tract) and parenteral (bypassing the gastrointestinal tract) routes of drug administration. Enteral: through the mouth (oral), under the tongue (sublingual) and through the rectum (rectal).

The introduction of drugs through the mouth is the most convenient and natural way for the patient. Absorption of drugs taken by mouth occurs mainly by simple diffusion of non-ionized molecules in the small intestine, less often in the stomach. At the same time, before entering the general circulation, the drugs pass through two biochemically active barriers - the intestines and the liver, where they are affected by hydrochloric acid, digestive (hydrolytic) and hepatic (microsomal) enzymes, and where most drugs are destroyed (biotransformed). The rate and completeness of absorption of drugs from the gastrointestinal tract depends on the time of the meal, its composition and quantity. So, on an empty stomach, acidity is less, and this improves the absorption of alkaloids and weak bases, while weak acids absorbed better after meals. Medications taken after a meal may interact with food ingredients, affecting their absorption. For example, calcium chloride, taken after a meal, can form with fatty acids insoluble calcium salts, limiting the possibility of its absorption into the blood.

Reception on an empty stomach also affects the manifestation of a side effect. For example, a nicotinic acid can cause angioedema, antibiotics lincomycin and fusidine sodium - complications from the gastrointestinal tract, etc. With the oral route of administration, side effects of drugs often manifest themselves in the oral cavity (allergic stomatitis and gingivitis, irritation of the mucous membrane of the tongue - "penicillin glossitis", "tetracycline tongue ulcers", etc.). Sometimes this route of administration is not possible due to the condition of the patient (diseases gastrointestinal tract, unconsciousness of the patient, violation of the act of swallowing, etc.). Some drugs, when administered orally, are destroyed in the acidic environment of the stomach (penicillins, insulins). Oil solutions (for example, preparations of fat-soluble vitamins) are absorbed only after emulsification, which requires fatty and bile acids. Therefore, in diseases of the liver and gallbladder, their introduction inside is ineffective.

Rapid absorption of drugs from the sublingual region (with sublingual administration) is provided by rich vascularization of the oral mucosa. With this method of administration, the drug is not destroyed by gastric juice and liver enzymes, the action occurs quickly (after 2-3 minutes). This allows you to enter sublingually some drugs for emergency, urgent care (nitroglycerin - for pain in the heart; clonidine - for hypertensive crises etc.) or drugs that break down in the stomach (some hormonal drugs). Sometimes, for quick absorption, drugs are used on the cheek (buccally) or on the gum in the form of films (trinitrolong).

The rectal route of administration is used less frequently (mucus, suppositories): in diseases of the gastrointestinal tract, in the unconscious state of the patient. Absorption from the rectum is faster than when administered orally. About 1/3 of the drug enters the general circulation, bypassing the liver, since the inferior hemorrhoidal vein flows into the system of the inferior vena cava, and not into the portal. The speed and strength of action with this method of administration is higher than with the introduction through the mouth.

Parenteral routes of administration: on the skin and mucous membranes, injections, inhalations.

When applied externally (lubrication, baths, rinses), the drug forms a complex with a biosubstrate at the injection site - a local effect (anti-inflammatory, anesthetic, antiseptic, etc.), in contrast to the resorptive one that develops after absorption.

Injections are administered medicinal substances that are not absorbed or destroyed in the gastrointestinal tract. This route of administration is also used in emergency cases to provide emergency assistance. When administered subcutaneously, the drug is absorbed through the capillaries and enters the general circulation. The effect develops in 10-15 minutes, its magnitude is greater, and the duration is shorter than when administered through the mouth.

Even faster absorption and, therefore, the effect occurs when administered intramuscularly. These injections are less painful than subcutaneous injections.

When administered intravenously, the drug immediately enters the blood (absorption as a component of pharmacokinetics is absent). In this case, the endothelium is in contact with a high concentration of the drug. To avoid toxic manifestations potent drugs are diluted with isotonic or glucose solution and administered, as a rule, slowly. Intravenous injections often used in emergency care. If the drug cannot be administered intravenously (for example, in burnt patients), to obtain quick effect it can be inserted into the thickness of the tongue or into the floor of the mouth.

To create a high concentration (for example, cytostatics, antibiotics) in certain body, the drug is injected into the leading arteries. The effect will be higher than with intravenous administration, and side effects will be less. For meningitis and for spinal anesthesia, subarachnoid drug administration is used. In cardiac arrest, adrenaline is administered intracardiac. Sometimes drugs are injected into the lymphatic vessels.

Inhalation of drugs (bronchodilators, antiallergic drugs, etc.) is used to affect the bronchi (local action), as well as to obtain a quick (comparable to intravenous administration) and a strong resorptive effect, since there are a large number of capillaries in the pulmonary alveoli, and intensive absorption of drugs occurs here. This way you can enter volatile liquids, gases, as well as liquid and solids in the form of aerosols.

Pharmacology: lecture notes Valeria Nikolaevna Malevannaya

2. Routes of drug administration

There are enteral and parenteral routes of drug administration. enteral route- the introduction of the drug inside through the mouth ( per os), or orally; under the tongue ( sub lingua), or sublingually; into the rectum ( per rectum), or rectally.

Taking the drug through the mouth. Advantages: ease of use; comparative safety, absence of complications inherent in parenteral administration.

Disadvantages: slow development of the therapeutic effect, the presence of individual differences in the rate and completeness of absorption, the effect of food and other drugs on absorption, destruction in the lumen of the stomach and intestines (insulin, oxytocin) or when passing through the liver.

Take medicinal substances inside in the form of solutions, powders, tablets, capsules and pills.

Application under the tongue (sublingually). The drug enters the systemic circulation, bypassing the gastrointestinal tract and liver, starting to act after a short time.

Insertion into the rectum (rectal). A higher concentration of drugs is created than with oral administration.

Suppositories (suppositories) and liquids are administered using enemas. The disadvantages of this method: fluctuations in the speed and completeness of the absorption of drugs, characteristic of each individual, inconvenience in use, psychological difficulties.

parenteral route- This different kinds injections; inhalation; electrophoresis; surface application of drugs to the skin and mucous membranes.

Intravenous administration (in / in). 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 action; the possibility of using substances that are destroyed, non-absorbable from the gastrointestinal tract. Disadvantages: with prolonged intravenous administration along the vein, pain and vascular thrombosis may occur, the risk of infection with hepatitis B viruses and human immunodeficiency.

Intra-arterial administration (in / a). It is used in cases of diseases of certain organs (liver, limb vessels), creating high concentration drug only in the relevant organ.

Intramuscular administration(in / m). Aqueous, oily solutions and suspensions of medicinal substances are administered. The therapeutic effect occurs within 10-30 minutes. The volume of the injected substance should not exceed 10 ml.

Disadvantages: the possibility of the formation of local soreness and even abscesses, the danger of accidentally entering the needle into a blood vessel.

Subcutaneous administration. Enter water and oil solutions. Do not inject subcutaneous solutions of irritating substances that can cause tissue necrosis.

Inhalation. Gases (volatile anesthetics), powders (sodium cromoglycate), aerosols are administered in this way. Inhalation of an aerosol achieves a high concentration of a medicinal substance in the bronchi with a minimal systemic effect.

Intrathecal administration. The drug 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 drugs are applied to the surface of the skin or mucous membranes.

electrophoresis It is based on the transfer of medicinal substances from the surface of the skin to deep-lying tissues using galvanic current.

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