Antibiotics: classification, side effects and interactions


Classification of antibiotics

According to the mechanism of action, they are divided into:

(a) antibiotics that inhibit cell wall synthesis, including penicillins, cephalosporins, fosfomycin and cycloserine.
Antibiotics acting on the wall are bactericides that act exclusively on bacteria in the active phase of their multiplication.
(b) antibiotics that inhibit protein synthesis, including aminoglycosides, tetracyclines, chloramphenicol and macrolides.
c) antibiotics that inhibit the replication mechanism and transcription of nucleic acids, including rifampicin and quinolones
d) antibiotics that alter the cytoplasmic membrane of bacteria or fungi, such as polymyxins.
(e) antibiotics acting as antimetabolites (sulphonamides, trimethoprim).

Families of antibiotics that are most commonly used are:

  • Beta-lactam compounds (which contain 1st, 2nd, 3rd and 4th generation penicillins and cephalosporins)

Penicillins are widely used to treat certain infections of the skin, breast and urinary tract. For example, a bladder infection (cystitis) is treated with penicillin.
The antibiotic most commonly used for cystitis and urinary tract infections is amoxicillin.
About 1 person in 15 will have an allergic reaction after ingestion and a very small number of patients will develop a serious allergic reaction (anaphylaxis).
Another problem resulting from the extensive use of these drugs is that some bacterial strains develop resistance to drugs.
Cephalosporins are broad-spectrum antibiotics, which means that they are effective in treating a variety of infections, including some serious ones, such as:
1) Septicemia – infection of the blood
2) Pneumonia
3) Meningitis – infection of the outer skin of the brain and spinal cord
4) Cystitis
In particular, cefixime is used.

  • Tetracyclines

Tetracyclines are another type of broad-spectrum antibiotic that is used for a variety of infections. Some trade names are: demeclocycline, doxycycline and minocycline.
They are widely used in the treatment of the so-called rosacea, which causes skin redness and severe acne.

  • Macrolides

Macrolides are a type of antibiotic used to treat infections of the lungs and thorax.
They can be a useful alternative for people who have an allergy to penicillin or in the treatment of antibiotic-resistant bacteria.

  • quinolones

They are effective in urinary tract infections, bacterial diarrhea, soft tissue, abdominal and respiratory infections.
Among these one finds: ciprofloxacin, norfloxacin.

  • Aminoglykoside

Aminoglycosides are a group of bactericidal antibiotics that are extensively used against gram-negative enterobacteria. They are irreversible inhibitors of protein synthesis. Some trade names are: gentamicin (Refobacin), tobramycin (TobraZid) and amikacin (Amikacin Fresenius).
Aminoglycosides are poorly absorbed in the digestive tract and are therefore administered intramuscularly and intravenously.
All are ototoxic (harmful to hearing) and nephrotoxic (harmful to kidneys), especially when used for more than 5 days, in high doses and in elderly patients.
Aminoglycosides are often given in combination with beta-lactam antibiotics to expand the spectrum of action.

Side effects

Most antibiotics (with the exception of aminoglycosides) do not cause serious problems and side effects are rather rare. The most common are:

  • Indisposition
  • Gastrointestinal disorders such as nausea, vomiting and diarrhea
  • Headache
  • Vertigo
  • Insomnia

General information and interactions

Some antibiotics are not suitable for people with certain pathologies, pregnant women or nursing mothers.
Antibiotics can also interact with other medications, including the birth control pill. It is therefore important to talk to the doctor when taking other medications.
For example, penicillin and ampicillin react with grapefruit: this can reduce the absorption capacity of the antibiotic.

Tetracyclines interact with minerals such as calcium, magnesium and aluminum, as well as with dairy products: these can reduce absorption and thus reduce the effectiveness of antibiotics.
In addition, tetracyclines also interact with anticoagulants.

Erythromycin reacts with theophylline, a drug used to treat asthma, by accumulating in blood levels.
Erythromycin also interacts with statins, which are drugs used to lower cholesterol. It increases the risk of muscle pain and interacts with anticonvulsants such as carbamazepine by enhancing its effects.

Fluoroquinolones interact with mineral salts such as calcium, magnesium and aluminum: these can reduce the effectiveness of the antibiotic.

The simultaneous use of antibiotics and alcohol can lead to side effects such as stomach pain, dizziness and drowsiness.
It should be remembered that some medicines for colds and mouthwash also contain alcohol. Therefore, one should pay attention to the description and avoid such funds while taking antibiotics.
Although alcohol does not reduce the effectiveness of the drug, it can decrease the patient’s energy and slow down the healing process of the condition.

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