Some symptoms observed in sick people can also occur in physiological conditions (for example, palpitations occur not only with damage to the cardiovascular system, but also with excitement, physical stress). Symptoms can be an expression of not only morphological changes (for example, enlargement of the liver, spleen), but also functional disorders (motor, secretory and others). Distinguish between symptoms characteristic of the defeat of any one system (for example, a cough is typical for damage to the respiratory system), and symptoms that occur when several systems are affected (for example, shortness of breath is typical for damage to the respiratory and cardiovascular systems).
The correct diagnosis is facilitated by a critical assessment of the identified symptoms, especially during questioning, given the possibility of aggravation, simulation and dissimulation. If a patient has several symptoms, one should try to establish their single mechanism of occurrence and determine the syndrome. The Medical Encyclopedia contains detailed descriptions of the symptoms of various diseases.
By the time of onset, the symptoms are divided into early and late (appear, respectively, in the early and late stages of the disease). The appearance of new symptoms during the course of the disease may raise the suspicion of a complication. According to their prognostic value, symptoms are divided into favorable, unfavorable and threatening.
According to the mechanism of therapeutic and prophylactic action, the medical reference book of medicines divides them into two large groups: some have this effect, changing the functions of certain physiological systems of the body, others - destroying microbes and parasites - causative agents of diseases.
There are also substitution therapy, when drugs are introduced into the body that make up for the lack of substances formed in the body and take part in the regulation of physiological functions. For example, the introduction of hormonal drugs in case of loss of the endocrine function of the corresponding gland. The effect of drugs on the body can be manifested at the site of its application, before it is absorbed into the blood.
In this case, the drug is absorbed rather slowly. This method of using drugs does not ensure the completeness of the entire dose taken into the bloodstream, since the drug can be more or less inactivated even before absorption under the influence of digestive juices, and after absorption - under the influence of liver enzymes. The sublingual way of using drugs has also become widespread: the drug is kept under the tongue until it is completely absorbed. With this method, the medicine enters the bloodstream, bypassing the stomach and liver.
When the drug is administered through the rectum, a greater completeness of absorption of the substance is provided than when it is introduced into the stomach, since the drug is not destroyed by enzymes in the rectum, and after absorption from the rectum it partially enters the bloodstream without entering the liver.
Chemical transformations of drugs in the body occur mainly in the liver, but to a greater or lesser extent they can be carried out in other tissues as well. The excretion of drugs is usually carried out by the kidneys. Gaseous substances and volatile liquids are released with exhaled air. Often, the glands of the gastrointestinal tract and sweat glands are also involved in the elimination of drugs from the body. When prescribing medications to nursing mothers, the possibility of excreting substances through the mammary glands should be taken into account.
As a result of repeated injections of drugs that are slowly excreted from the body and are slowly inactivated in it, their accumulation in concentrations exceeding therapeutic ones is possible. This phenomenon is described in the medical encyclopedia and is called cumulation. The body gradually loses sensitivity (addiction) to some drugs when they are repeated. In such cases, you have to gradually increase the dose.
To drugs that act on the central nervous system and cause a state of euphoria (pleasant mood), pathological addiction may occur (see Drug addiction). Stopping the drug that has caused the addiction leads to a number of severe disorders of the physical and mental state of the body.
The effect of drugs depends on the state of the body. The age of the patient is of great importance. As a rule, children are more sensitive to drugs. Accordingly, in a medical reference book in a special table, the highest permissible doses of poisonous and potent substances for children of different age groups are given.
In old age, drug sensitivity also increases. Therefore, it is customary when prescribing certain drugs to persons over 60 years of age to reduce the dose to 50%.
Individuals have an unusually high sensitivity to certain drugs, which is called idiosyncrasy.
With idiosyncrasy, the body's reaction to the effects of drugs is of an allergic nature, manifested by urticaria, edema of the mucous membranes, swelling of the joints, and fever (see Medicinal disease). With extreme caution, medications should be prescribed to pregnant women, as they can disrupt the processes of laying and development of tissues and organs of the fetus, which leads to congenital deformities.