Oral Antibiotics: “Strong” and “Weak”

Myths and scientific facts about the effectiveness and safety of antibacterial drugs

Scientists claim that bacteria have existed on Earth for at least 3, 8×109 years, while antibiotics have been used in clinical practice only since the 40s of the last century. But even this time was enough for the drugs of this group to become overgrown with a lot of myths that interfere with effective antibiotic therapy. Despite the fact that treatment with antimicrobial agents is a priori impossible without the direct guidance of a doctor, a modern “reasonable patient”, influenced by near-scientific data, makes an “invaluable contribution” to the cause of antibiotic resistance and other negative consequences of incorrect use of antibiotics. A competent pharmaceutical specialist who has the correct information about antimicrobial agents and is ready to share it with the client can warn him against rash decisions.

Please note that it is necessary to use antibiotics as prescribed by a doctor. Buy antibiotics online at Antibiotics-antibacterials.net

Myth: Modern antibiotics are so “strong” that no bacteria can resist them

Truth. In fact, one of the most urgent problems of modern pharmacology and healthcare in general is the rapid development of resistant strains of bacteria, including those resistant to modern antibiotics of recent generations. The occurrence of resistance has been registered for each class of antimicrobial drugs without exception. It can develop at any stage of achieving a therapeutic effect (and even at several at once). The main mechanisms of sustainability development:

  • Initially resistant strains. For example, some gram-negative bacteria have external cell membranes that protect their cells from the action of a number of penicillins and cephalosporins.
  • Spontaneous mutations that lead to the appearance of organisms resistant to antibiotics.
  • The transfer of antimicrobial resistance genes is the most common and important mechanism for the development of antibiotic resistance.

Antibiotic resistance is a global problem that can have unpredictable consequences for each of us. Unfortunately, consumers themselves make a huge contribution to its existence. It is appropriate to remind customers with prescriptions for antibiotics about this, emphasizing that taking antimicrobial drugs only as prescribed by a doctor and strict compliance with the dose and regimen of antibiotic therapy can significantly reduce the risks of developing resistant strains.

Myth. To get cured faster, you need” strong ” broad-spectrum antibiotics

Truth. All registered antibacterial drugs can be safely attributed to powerful, that is, “strong”, but the severity of their antimicrobial effect depends on many factors united by the principles of antibiotic therapy:

  • The diagnosis is as accurate as possible. Knowledge of the diagnosis allows you to determine the suspected pathogen.
  • Determination of the pathogen, if possible.
  • Making an informed decision about the need to prescribe antibiotics.
  • Selection of the optimal antibiotic, taking into account the pharmacokinetics and spectrum of activity.
  • Selection of the optimal dose and course of treatment (the latter for most acute infections should be at least 5-10 days).
  • Monitoring the effectiveness of antibiotic therapy.

Control over the use of antibiotics, frankly speaking, is insufficient, the issue of incorrect selection of drugs is especially acute. It is known that it is carried out in two ways: etiotropic and empirical. In the first case, the antibiotic is used purposefully against a specific, precisely established pathogen. Without a doubt, this is rational and justified. However, the identification of the microorganism that caused the infection takes time, usually it takes several days. When the process is acute and the patient needs immediate help, the isolation of the pathogen is an unjustified luxury. In such a situation, empirical therapy is prescribed, selecting the drug taking into account the most likely pathogens [3]. For example, the most common causative agent of pneumonia is pneumococcus, cystitis is E. coli, and so on.

If the antibiotic was selected correctly and all the other principles of antibiotic therapy were followed, it will undoubtedly turn out to be “strong”. But the same drug, used incorrectly (regardless of at what stage the mistake was made), may show “weakness” and not have a therapeutic effect.

Myth: Although many sulfonamide drugs are almost a thing of the past, co-trimoxazole still retains its position among antimicrobial drugs

Truth. Sulfonamides were the first effective chemotherapeutic agents successfully used for the prevention and treatment of bacterial infections. And although the scope of their use has significantly narrowed with the advent of penicillin, and later other antibiotics, some of their representatives have long occupied a niche in the range of antimicrobial drugs. This is primarily a synergistic combination of trimethoprim and sulfamethoxazole, known as INN co-trimoxazole.

Co-trimoxazole is a powerful selective inhibitor of microbial dihydrofolate reductase, an enzyme that reduces dihydrofolate to tetrahydrofolate. Blocking this reaction provides a violation of the formation of purine and pyrimidine bases, nucleic acids and thus inhibits the growth and reproduction of microorganisms. However, in recent years, the number of bacterial strains resistant to co-trimoxazole has increased dramatically, and the prevalence of resistance continues to increase rapidly.

It is assumed that previously drug-sensitive microorganisms in the course of evolution acquired extra-chromosomal DNA molecules (plasmids) that encode an altered dihydrofolate reductase. Thanks to them, resistance to co-trimoxazole is formed in almost every third isolate of Escherichia coli in the urine. The situation with other strains of bacteria previously sensitive to the drug is not much better. In this regard, today the use of co-trimoxazole is sharply limited, and the drug has almost given way to more effective and safe antimicrobial drugs.

Myth: Oral cephalosporins are as “strong” as parenteral ones

Cephalosporins (CS) are one of the most extensive classes of antimicrobial drugs, presented both in oral and parenteral forms. At the same time, the severity of the antibacterial effect is primarily determined by belonging to one of the four generations. Antibiotics of the 1st generation cephalosporins-parenteral cefazolin and oral cephalexin-have the narrowest spectrum of activity, similar to the spectrum of aminopenicillins (ampicillin, amoxicillin).

Cephalosporins of the second generation (parenteral cefuroxime, oral cefaclor) are active against gram-negative bacteria, while they are close to their predecessors in their action on staphylococci and streptococci. Thus, the power of representatives of antibiotics of the first and second generations practically does not depend on the dosage form. But with the cephalosporins of subsequent generations, everything is not so simple.
It is known that antibiotics of the 3rd generation have a higher activity against Gram-negative bacteria, pneumococci and streptococci compared to CS-I and CS-II. However, their oral forms cefixime and ceftibutene definitely have a narrower spectrum of activity than parenteral ceftriaxone, ceftazidime and cefoperazone. In particular, oral medications do not work against penicillin-resistant pneumococci, which is associated with their relatively low bioavailability. Thus, the bioavailability of cefixime is only 40-50 %, while in parenteral forms it is close to 100 %.

Nevertheless, Cefixime is considered a powerful antibiotic, the use of which is justified for urinary tract infections, as well as otitis media and pharyngitis. Ceftibutene is used much less often: it is indicated only for the treatment of acute bacterial complications of chronic bronchitis, otitis media, pharyngitis and tonsillitis. A significant disadvantage of this drug is its low activity against Staphylococcus aureus. At the same time, parenteral cephalosporins of the third generation are widely used for the treatment of severe infections of the upper, lower respiratory tract, biliary tract, soft tissues, intestinal infections, sepsis and others.

Myth. Chloramphenicol is a “strong” safe antibiotic for intestinal infections

Truth. On the one hand, chloramphenicol really has a wide range of activity, including gram-positive and gram-negative cocci, gram-negative rods, including intestinal and hemophilic, as well as other pathogens of intestinal infections — salmonella, shigella, and so on. But, on the other hand, the drug is associated with an equally wide range of adverse reactions.

It is known that chloramphenicol inhibits hematopoiesis, causing thrombocytopenia, anemia and even fatal aplastic anemia (although only in 1 case per 10,000-40,000 patients). In addition, it has hepatotoxic, neurotoxic effects and shows other side effects. Due to the extremely unfavorable safety profile, chloramphenicol is considered a reserve antibiotic and is prescribed only in cases where the benefit of its use exceeds the risk of side effects. This happens, as a rule, if for some reason it is not possible to choose another antibacterial drug.

Myth: Tetracyclines are traditionally “weak” antibiotics, much less powerful than penicillins

Truth. In fact, tetracyclines have a wide range of antibacterial activity, and their modern representatives act against even more bacteria than their predecessors, including a number of pathogens resistant to other classes of antibiotics. Thus, tigecycline, which appeared on the market only in the mid-2000s, was developed as part of a program to combat the growing antibiotic resistance of such “complex” pathogens as staphylococcus aureus and E. coli.

Tetracyclines, including tetracycline and doxycycline, which have been used for decades, are able to penetrate into the cell, so they are still widely used today for the treatment of intracellular sexually transmitted infections (chlamydia, ureaplasmosis, mycoplasmosis). The indications for their appointment include a helicobacter infection — as part of eradication therapy. Due to their effectiveness against Propionibacterium acne, tetracyclines, along with macrolides, are used to treat acne. Minocycline, whose spectrum includes Neisseria meningitidis, is used to prevent meningococcal infection.

As a fly in the ointment, it should also be mentioned that most tetracyclines (with the exception of modern representatives) are characterized by a high level of secondary resistance of many bacteria and, moreover, cross-resistance of microorganisms. And this, of course, in many cases reduces their relevance.

Myth. Fluoroquinolones are too “strong” antibacterial drugs, so they are not used for the treatment of children

Truth. Fluoroquinolones are an extensive group of antimicrobial drugs, including representatives of four generations. Today, quinolones of the last three generations are used, and antibiotics belonging to the III (levofloxacin, sparfloxacin, gatifloxacin) and IV (moxifloxacin, clinafloxacin) generations have the greatest activity. Their spectrum of activity includes pneumococci, including penicillin-resistant, atypical pathogens (chlamydia, mycoplasma), most gram-negative bacteria, streptococci, anaerobes and others. The absolute advantages of modern quinolones include resistance to beta-lactamases, slow development of resistant strains, high bioavailability of oral forms of drugs, low toxicity, as well as the duration of action, which allows prescribing many drugs 1 time a day.

Fluoroquinolones are the drugs of choice for urinary, biliary, respiratory tract infections, sexually transmitted infections, gynecological diseases, and so on. But for all their advantages, fluoroquinolones also have a number of disadvantages, including the possibility of damage to the cartilaginous points of bone growth in children. However, this effect was revealed during toxicological studies on immature animals. According to clinical data, the total number of side effects of fluoroquinolones — both in quantity and quality-does not differ in children and adults.

Myth: Erythromycin is a “weak” macrolide, much inferior to modern representatives of this class of drugs

Truth. Erythromycin, as well as other macrolides, reversibly binds to the 50S subunit of ribosomes, disrupting the process of translocation and formation of peptide bonds between amino acid molecules and blocking the synthesis of proteins of sensitive bacteria. Despite the existence of modern representatives of the class — azithromycin, clarithromycin and others-erythromycin is still considered the drug of choice for the treatment of a number of infections, in particular, mycoplasma infection in children, legionellosis, diphtheria and whooping cough.

Along with the high activity, erythromycin is not sufficiently well tolerated. It is known that in 30-35% of patients it causes dyspepsia, and also has a number of other side effects. In this regard, in practice, modern representatives of this group are often preferred.

Myth. Amoxicillin is as strong an antibiotic as amoxicillin clavulanate – in fact, it is the same drug

Truth. Amoxicillin, along with ampicillin, refers to extended-spectrum aminopenicillins that act against gram-positive and gram-negative bacteria. It is still considered the most active among all oral lactam antibiotics against penicillin-sensitive and penicillin-resistant pneumonic staphylococci. However, it should be taken into account that a number of bacteria have developed resistance to penicillins and aminopenicillins in particular. So, resistant strains of hemophilic bacillus, pneumococcus, enterobacteria are widely distributed. The way out of this situation is the use of inhibitor-protected aminopenicillins, such as amoxicillin/clavulanate and ampicillin/sulbactam, resistant to the action of beta-lactamases and having, respectively, a wider spectrum of activity.

Thus, the appointment of aminopenicillins is justified for mild and uncomplicated infections, while inhibitor-protected drugs are indicated for severe and recurrent forms. In this case, the route of administration (parenteral or oral) is chosen depending on the severity of the infection.

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