Respiratory diseases remain a major problem in pediatrics and clinical medicine in general. They consistently lead in the structure of the overall morbidity of children and adolescents, occupying more than half of it. Over the past six years (2012–2017), the incidence of ARVI in the population of the Russian Federation has increased by 9.3%. Children under 17 continue to predominate in the age structure of the incidence , in 2017 their share increased compared to 2016 (72.52%) and amounted to 73.16%. In general, the incidence among the child population is 3.7 times higher than that of the total population. Like in previous years, in 2017 the maximum incidence was observed in the age groups 1-2 years – 119,128.09 per 100 thousand (2016 – 120,694.54) and 3-6 years – 115,807.03 per 100 thousand (2016 - 117,761.08). The high incidence of acute diseases of the respiratory tract is explained by a variety of etiological factors, as well as the ease of transmission of pathogens, their significant variability and contagiousness. Most ARIs are viral in nature (influenza, parainfluenza, metapneumovirus, respiratory syncytial virus, adenoviruses (more than 50 types), reoviruses, bocavirus, rhinovirus, coronaviruses, etc.), less often bacterial (pneumococcus, Haemophilus influenzae), and in some cases they can be caused by atypical flora (mycoplasma, chlamydia, legionella, pneumocystis), which during epidemic outbreaks can reach 25-50% in the etiological spectrum. Cough with ARVI is a frequent clinical symptom, regardless of the exposure level: the upper or lower respiratory tract. Therefore, the use of mucolytic and expectorant drugs is pathogenetically justified. Along with traditional (reflex action) expectorants, today the doctor's tool kit has been replenished with a number of modern mucoactive drugs. The cough is an unconditioned defense reflex with elements of conscious control. The main role of the cough is to clear and restore the airway. Effective mucociliary clearance is of great importance in ensuring this function.

In the clinical assessment of cough, it is necessary to pay attention to the following characteristics: its frequency; the number of cough shocks; rhythm; timbre (voiced/dull); sonority (silent, loud, quiet, rough); character; intensity (semicough, light, severe); periodicity (constant, periodic, paroxysmal); soreness; productivity; the nature of the sputum; time of appearance (morning, afternoon, evening, night cough); position of the body at the time of coughing; duration (episodic, paroxysmal, constant); period; the presence of factors provoking a cough (tobacco smoke, cold air, emotional overload, etc.); the presence of other symptoms.

 Cough can be divided into dry (nonproductive, low productive) and wet (productive, i.e, a cough that is accompanied by hyperproduction of bronchial mucus. In children under 5 years old, it is difficult to determine whether a cough is productive, since at this age they try not to cough up, but to swallow phlegm. Their cough is often accompanied by vomiting, and the color of the sputum can be determined in the vomit.

An ineffective cough is a cough that does not sufficiently perform its drainage function, which can contribute to the accumulation of mucus in the bronchi, activation of bacterial infection, deterioration of bronchial patency, and the development of atelectasis. The known complications, the development of which can result in severe cough, are emphysema, pneumothorax, heart rhythm disturbances, cough fainting syndrome, diaphragmatic hernia, urinary incontinence, rib fracture, etc.

In terms of duration, it is advisable to distinguish between acute cough - up to 4 weeks, subacute/prolonged - from 4 to 8 weeks, and chronic cough - more than 8 weeks. As a rule, acute cough with ARVI has a favorable course. At the onset of an acute respiratory infection, the cough is usually dry, but later is replaced by wet cough, spontaneously or under the influence of secretion-stimulating therapy, which in itself brings relief to the child. Most often, with ARVI, the cough disappears in 14 days, but in some cases the cough persists for 3-4 weeks. Most diseases accompanied by a lingering cough from 4 to 8 weeks are associated with acute viral and pertussis-like infections. It is therefore recommended that follow-up (up to 8 weeks) be undertaken to decide whether further in-depth studies are indicated.

For acute and chronic respiratory diseases, expectorant and mucolytic drugs are among the most commonly prescribed drugs in pediatric practice and not only. However, a number of unresolved issues lead to ongoing discussions on the optimal choice of mucoactive drugs. Therefore, the development of algorithms for mucolytic and expectorant therapy is especially relevant both scientifically and practically for a wide range of pediatricians, pulmonologists, allergists, and general practitioners. With ARI of the lower respiratory tract (tracheitis, bronchitis), accompanied by dry cough, as well as with a non-productive wet cough, drugs that stimulate secretion are prescribed, most often in the initial period of the disease. At the same time, traditional expectorant phytopreparations, secretolytics, or their combinations can benefit. Note that with a dry cough, antitussives are prescribed infrequently, in a short course, only with a significant effect on the well-being, the night's sleep of the child. In acute inflammatory processes in the respiratory tract, when there are still no evident structural changes in the goblet cells and ciliated epithelium, phytopreparations are most effective as expectorants. Traditional herbal expectorants for many centuries continue to be widely used in pediatric practice and beyond. Modern official phytopreparations contain a strictly dosed amount of constituent substances, which can ensure safety and sufficient effectiveness of treatment. Herbal expectorants, when taken orally, have a moderate irritating effect on the stomach receptors, thus activating the vomiting center of the medulla oblongata, reflexively enhancing the secretion of the salivary glands and mucous glands of the bronchi. The principle of these drugs are alkaloids and saponins, which promote mucus rehydration by increasing plasma extravasation, enhancing the motor function of the bronchi and expectoration by activating the gastropulmonary reflex, stimulating the peristaltic contractions of the bronchi and increasing the activity of the ciliated epithelium. It should be considered that the manifestation of the pharmacological effects of phytopreparations requires a longer period, and, therefore, the improvement occurs somewhat more slowly compared to their synthetic counterparts. The combination of various medicinal components in one drug can more effectively improve mucociliary clearance due to the synergism of their interaction, relieve a complex of pathological symptoms, and also reduce the number of drugs used, the risk of side effects, and at the same time increase the compliance of therapy.

Along with traditional (reflex action) expectorants, a number of mucoactive drugs of direct and indirect action are currently used, including mucolytics (acetylcysteine, erdosteine, proteolytic enzymes), secretolytics (bromhexine, ambroxol), mucoregulators (carbocysteines). The main purposes of the ongoing mucoactive therapy are to reduce the formation of sputum, its rehydration, dilution, and stimulation of excretion. However, they all of them have different chemical structures and mechanisms of action. N-acetylcysteine ​​derivatives are highly active mucolytic drugs, which have been widely used in clinical practice for over 50 years. Acetylcysteine ​​has a more pronounced ability to liquefy viscous purulent sputum than other mucolytics. It  reduces the sputum viscosity and elasticity and effectively lyses fibrin and blood clots. The action of acetylcysteine ​​is based on its ability to destroy disulfide bonds (S – S) to sulfhydryl groups (–SH) in mucoproteins of bronchial secretions, which depolymerizes secretions and facilitates the removal of sputum. Many in vitro studies have shown that acetylcysteine ​​effectively inhibits the formation of biofilms, destroys previously formed biofilms (both initial and mature), and reduces the viability of bacteria in biofilms. Naturally, when choosing a drug that can affect the secretory function of the mucous membrane or the bronchial secretion itself and its evacuation, an individual approach is required. Empirical (without establishing the cause) treatment of cough often fails to give the expected effect. In order to improve the drainage function of the bronchial tree, a set of therapeutic measures is used, including adequate hydration (for effective liquefaction and evacuation of sputum), inhalation and kinesitherapy, mucoactive drugs, and bronchodilators in case of broncho-obstructive syndrome. Thus, cough therapy for ARVI should be comprehensive, individually targeted, adequate for the etiology, nosology, severity of the course of the disease and should focus on all links of pathogenesis, as well as provide for compliance with the patient.

Source: Melnikova I.M., Mizernitskiy Yu.L. Individually oriented choice of mucolytic drug for coughing in a child with ARVI. Medical advice. 2019; 2: 224-230. DOI: https://doi.org/10.21518/2079-701X-2019-2-224-230