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All macrolides demonstrate a similar mechanism of action based on the inhibition of RNA-dependent synthesis of protein molecule elongation in sensitive microorganisms. Antibiotics reversibly bind to the 50S subunit of the bacterial ribosome, resulting in the blockade of transpeptidation and/or translocation, the growing tRNA-polypeptide chain is prematurely cleaved off, causing the termination of the assembly of the protein molecule. The nature of the antimicrobial action of Biaxin is bacteriostatic in most cases, but under certain conditions (depending on the type of microorganism, the concentration of the antibiotic and the size of the inoculum), a bactericidal effect is possible against microorganisms such as S. pneumoniae and S. pyogenes.

The antimicrobial effect against H. influenzae and S. pneumoniae of azithromycin and to some extent Biaxin depends on the concentration created in the focus of infection, and for other macrolides - on maintaining the concentration above the minimum suppressive concentration (MPC) for at least 40-50% of the time interval between doses.

Biaxin, like a number of other macrolides, has anti-inflammatory, immunomodulatory and mucoregulatory properties that manifest independently of its antibacterial activity. Among other things, macrolides, including Biaxin, contribute to reducing the hyperreactivity of the bronchial tree, have a beneficial effect on the clearance of bronchial and nasal secretions. Studies show that their use leads to a decrease in sputum production in patients with excessive secretion, which is typical for diseases such as COPD, diffuse panbronchiolitis, chronic sinusitis.

The widespread use of macrolides causes an increase in resistance among strains of S. pneumoniae and S. pyogenes — the main pathogens of community-acquired pneumonia and acute tonsillitis/pharyngitis, respectively. It is known that the resistance of microorganisms to macrolides is mainly (more than 90%) determined by two main mechanisms: modification of the target of their action (this occurs due to the production of the enzyme Erythromycin resistance methylase by microorganisms) and active excretion of the drug (efflux) from the microbial cell.

Under the action of methylase, 14-, 15- and 16-membered macrolides, lincosamides and streptogramin B lose their ability to bind to ribosomes (MLSB phenotype), and the microorganism acquires a high level of resistance (MPC >32-64 mg/L). This resistance mechanism is characteristic of S. pneumoniae, S. aureus, S. pyogenes and a number of other microorganisms.

Another common mechanism of resistance to macrolides is due to the removal of the drug from the microbial cell (M-phenotype). As a result, resistance to 14- and 15-membered macrolides is formed, but less pronounced (MPC = 1-32 mg/l) than in cases of MLSB resistance phenotype. Strains with the M-phenotype of resistance retain sensitivity to 16-membered macrolides, ketolides, lincosamides, streptogramines of group B. Efflux is characteristic of S. pneumoniae, S. pyogenes, S. epidermalis, S. aureus, Enterococcus spp.

It is interesting to note the fact that the risk of selection of drug-resistant microorganisms (for example, S. pneumoniae) depends on the duration of the half-life of a macrolide, being less in Biaxin (half-life - 5-6 hours) compared with Azithromycin (half-life - 35-76 hours). This is due to the long-term preservation of azithromycin in the body in low (sub-inhibitory) concentrations, which are not able to suppress the growth of microorganisms, but, nevertheless, can cause mutations that contribute to the development of resistance.

Methylation of the erythromycin hydroxygroup at the C6 position improves acid resistance, which allows Viaxip to be better absorbed from the gastrointestinal tract (gastrointestinal tract). In addition, at low pH values, Biaxin does not break down into elements responsible for the occurrence of a significant part of the side effects, which is observed, in particular, when using erythromycin. When ingested, Biaxin is rapidly absorbed into the gastrointestinal tract, its maximum concentrations in the blood are reached after 1-2 hours. Bioavailability is 52-55%, increases slightly when taken with food, in elderly patients. The serum concentration of the antibiotic when taken orally varies from 1 mg / l (taking 250 mg 2 times a day) to 2-3 mg / l (when using 500 mg 2 times a day); 42-70% of the drug binds to plasma proteins.

An important feature of Biaxin is the ability to accumulate in polymorphonuclear neutrophils, macrophages, monocytes — the concentrations of the drug in alveolar macrophages exceed extracellular ones by 94 times, and in mononuclears - by 20 times [15]. The maximum accumulation of the drug is observed in the lung tissue, fluid lining the mucous membrane of the bronchi and alveoli, bronchial secretions, saliva, tonsils, middle ear, sinuses, gastrointestinal mucosa, prostate, conjunctiva and eye tissues, skin, bile, urethra, uterus, appendages and placenta. In particular, the concentration of the drug in the fluid lining the alveoli - hundreds of times, and in alveolar macrophages — thousands of times higher than that in the blood serum.

Biaxin is intensively (by 78%) metabolized in the liver by oxidative N-demethylation and hydroxylation with the participation of the cytochrome P450 system; the main metabolite (20%) is microbiologically active 14-GCM. About 20-30% of the administered dose is excreted through the kidneys unchanged, 10-15% - in the form of metabolites. The half-life (T1 / 2) when taken at a dose of 250 mg 2 times a day is 3-4 hours and increases to 7-8 hours when the dose is increased to 500 mg 2 times a day. With renal insufficiency (glomerular filtration <30 ml / min), there is a significant increase in T1/ 2 (up to 30-45 h), therefore, correction of the dosage regimen of the drug is necessary. In severe liver diseases, the proportion of renal excretion of Biaxin increases; T1/2 may increase slightly, but correction of the drug administration regimen is not required. Severe liver dysfunction is accompanied by a significant decrease in the formation of 14-GCM.

The most typical when using Biaxin are undesirable drug reactions (NLR) from the gastrointestinal tract - diarrhea, nausea, taste changes, occurring with a frequency of about 3% in adults. Sometimes, against the background of taking the drug, there is an increase in the activity of hepatic transaminases. Most NLR when taking Biaxin are poorly expressed and are transient in nature. Compared with erythromycin, it is characterized by a significantly lower frequency of NLR from the gastrointestinal tract in adults and less often causes NLR, leading to discontinuation of the drug (13% compared to 32%, respectively; p<0.01). Preparations of the macrolide group do not have cross-allergic reactions with antibiotics containing the b-lactam ring (penicillins, cephalosporins), which allows them to be used in people with allergic reactions to b-lactam antibiotics. Cases of allergic reactions to macrolides are extremely rare.

According to the results of the international multicenter study PROTEKT (2002), the prevalence of S. pneumoniae strains resistant to erythromycin was 31.5%. In Europe, the resistance of pneumococci to macrolides in 2000-2001 varied widely - from 12.2% (Great Britain) to 36.6% and 58.1% (Spain and France, respectively). However, in the Russian Federation, there are data on the resistance of clinical strains of S. pneumoniae obtained during the multicenter PEGASUS study (1999-2005) showed that the resistance of pneumococcus to macrolides remains low: the frequency of detection of strains that are not sensitive to 14- and 15-membered macrolides (Erythromycin, Biaxin, Azithromycin) is 6-9%, to 16-membered macrolides (spiramycin, midecamycin) and lincosamides is 4.5%.

From 61 to 95% of H. influenzae strains, both producing and not producing b-lactamases, are sensitive to Biaxin. At the same time, the average values of MIC50 and MIC90 Biaxin are about 2 times higher than those of azithromycin, however, a possible underestimation of the activity of the drug should be taken into account here, since the activity of the 14-GCM metabolite is similar to that of azithromycin. In relation to a number of H. influenzae strains, the combined inhibitory activity of Biaxin and 14-GCM turns out to be friendly, and in some cases synergistic.

In relation to M. catarrhalis, there were no significant differences between the values of MPC for different macrolides, while both Biaxin and erythromycin demonstrate high activity against this microorganism.

According to modern epidemiological studies conducted in Europe and North America, COPD affects from 4 to 10% of the adult population. At the same time, COPD ranks 4th in the overall structure of mortality among people over 45 years of age (second only to cardiovascular, cerebrovascular diseases and pneumonia), annually causing the death of more than 2.75 million people. In terms of economic costs, COPD occupies a leading place among respiratory diseases. In particular, in the United States, the annual health care costs for the treatment of COPD patients in 2002 amounted to $18 billion, and the total economic damage from the disease exceeded $32 billion. According to official data of the Ministry of Health and Social Development of the Russian Federation, 2.4 million COPD patients have been registered in Russia, but data from selective epidemiological studies suggest that their number may be about 16 million people.

It has been established that patients with COPD suffer from 1 to 4 or more exacerbations of the disease during the year, and it is the frequency of exacerbations that is one of the most important factors determining the quality of life of COPD patients, the rate of disease progression and economic losses.

According to modern concepts, up to 75-80% of COPD exacerbations are of an infectious nature, and the most likely pathogens are untyped strains of H. influenzae, as well as S. pneumoniae and M. catarrhalis, whose specific gravity, according to various researchers, is 13-46%, 7-26% and 9-20%, respectively. Biaxin, as already noted above, has high activity against pneumococcus and M. catarrhalis, and due to the active metabolite of 14-GCM, it also demonstrates clinically significant activity against H. influenzae. The clinical and microbiological efficacy of the antibiotic in the treatment of infectious exacerbation of COPD has been confirmed by the results of numerous studies.

In this regard, the results of a meta-analysis performed by I.I. Siempos and co-authors (2007) are indicative, during which a comparative assessment of the effectiveness and safety of the use of macrolides, respiratory fluoroquinolones and amoxicillin/clavulanate in the treatment of patients with exacerbation of chronic bronchitis of bacterial nature was carried out. The authors analyzed 19 randomized controlled trials in which macrolides demonstrated comparable efficacy with b-lactam antibiotics and fluoroquinolones in the treatment of patients with infectious exacerbation of COPD (Fig. 3, 4). However, it was noted that the use of fluoroquinolones was characterized by higher microbiological efficacy and a lower frequency of relapses of chronic bronchitis compared with macrolides, whereas the use of Amoxicillin / clavulanate was accompanied by the highest frequency of adverse drug reactions compared with other drugs.

In this regard, the position of Biaxin (along with azithromycin and amoxicillin) as the drug of choice for the treatment of patients suffering a simple (uncomplicated) exacerbation of COPD seems logical.

Biaxin has been registered by the Food and Drug Administration (FDA) In 1991, and for more than 15 years of clinical use, it continues to be a highly effective antibacterial drug for the treatment of community-acquired respiratory tract infections. Optimal pharmacokinetic characteristics of the drug, activity against topical microorganisms allow it to be used with predictable success in the treatment of patients with uncomplicated infectious exacerbation of COPD.