Antibiotics: Antibacterial Drugs

Products

Antibiotics (singular: antibiotic) are commercially available in the form of tablets, dispersible tablets, capsules, as infusion preparations, suspensions and syrups for children, and as granules, among others. There are also some topical preparations, such as creams, ointments, eye drops, eye ointments, ear drops, nasal ointments and sore throat tablets. The first active ingredient from this group to be marketed was arsphenamine (Salvarsan) in 1910, an arsenic compound for the treatment of syphilis developed under the direction of Paul Ehrlich. Penicillin was discovered in September 1928 at St. Mary’s Hospital in London by Alexander Fleming. And in the 1930s, sulfamidochrysoidine (Prontosil), the first sulfonamide, came on the market. Tetracyclines and cephalosporins were discovered in the 1940s and macrolides in the 1950s. Some antibiotics are combined with agents that reverse resistance. The best-known examples are beta-lactamase inhibitors such as clavulanic acid.

Structure and properties

Many antibiotics can be classified into groups based on chemical structural elements. These include, for example, the beta-lactam antibiotics, the tetracyclines, the quinolones, and the macrolides. It is often forgotten that many antibiotics have a natural origin and were isolated primarily from fungi or bacteria. Semi- and fully synthetic derivatives have been produced from the natural starting materials.

Effects

Antibiotics have bacteriostatic to bactericidal properties, meaning they inhibit the growth of bacteria or kill them. They interact selectively with specific bacterial structures. Typical mechanisms of action include, for example:

  • Inhibition of protein synthesis
  • Inhibition of cell wall synthesis
  • Inhibition of DNA replication
  • Blockade of folic acid metabolism
  • Damage to macromolecules such as DNA and proteins.
  • Disruption of the cell membrane

Antibiotics differ in their spectrum of activity, for example, with respect to Gram-positive, Gram-negative, aerobic, anaerobic, and intracellular bacteria.

Indications

For treatment and, less commonly, prevention of bacterial infectious diseases with susceptible pathogens. Other indications exist for some agents. For example, tetracyclines are used for acne and rosacea. Some antibiotics are also approved for parasitic diseases such as malaria.

Dosage

According to the prescribing information. Drugs are usually administered perorally, parenterally, or topically. When administered, the possible influence of food on bioavailability or tolerability must be considered. Liquid antibiotic suspensions must be shaken before use. Antibiotics are usually given for a specific duration of therapy (e.g., 3 days, 5 days, 7 days, 10 days, 14 days) or sometimes as a single dose. Antibiotics can be combined with probiotics to prevent gastrointestinal symptoms. If these contain live bacteria, they must be given at a time interval. Antibiotics can make the skin sensitive to sun or UV radiation. Therefore, severe sunburn may occur during sunbathing. Therefore, the skin should be well protected during treatment.

Active ingredients

This list shows a selection of important representatives. For complete information, see drug groups and active ingredients: Aminoglycosides:

  • Gentamicin
  • Neomycin
  • Streptomycin
  • Tobramycin

Beta-lactam antibiotics:

Quinolones:

  • Ciprofloxacin
  • Levofloxacin
  • Moxifloxacin
  • Norfloxacin

Fenicole:

  • Chloramphenicol

Folic acid antagonists:

Glycopeptide antibiotics:

  • Vancomycin
  • Teicoplanin

Lincosamide:

  • Clindamycin

Macrolides:

  • Azithromycin
  • Clarithromycin
  • Erythromycin

Nitrofurans:

  • Nitrofurantoin

Nitroimidazoles:

  • Metronidazole
  • Ornidazole

Oxazolidinones:

  • Linezolid

Phosphonic acid derivatives:

  • Fosfomycin

Pleuromutilins:

  • Retapamulin

Polymyxins:

  • Colistimethate

Polypeptide antibiotics:

  • Bacitracin
  • Gramicidin
  • Tyrothricin

Rifamycins:

  • Rifabutin
  • Rifampicin
  • Rifamycin
  • Rifaximin

Steroid antibiotics:

  • Fusidic acid

Tetracyclines:

  • Doxycycline
  • Minocycline

Tuberculostatics Cyclic lipopeptides:

  • Daptomycin

Contraindications

Contraindications depend on the active ingredient used. A selection:

  • Hypersensitivity, also to related substances.
  • Some representatives must not be used in children and adolescents, pregnant women and during lactation.

Full precautions can be found in the drug label.

Interactions

Prior to therapy, potential drug-drug interactions must be considered. Antacids, minerals, and trace elements may reduce the absorption of antibiotics, for example, tetracyclines and quinolones. Some agents interact with CYP450 isoenzymes, such as macrolides, the quinolones, and the rifamycins. Antibiotic treatment may affect the safety of hormonal contraceptives because the enterohepatic circulation is disturbed by the change in intestinal flora. Therefore, contraception should be used with an additional method, such as a condom. Beta-lactam antibiotics are organic anions that undergo active tubular secretion at the kidney. Interactions are possible via this mechanism.

Adverse effects

The most common and typical possible adverse effects of antibiotics include:

  • Gastrointestinal disturbances such as diarrhea, nausea, vomiting, abdominal pain, loss of appetite
  • Hypersensitivity reactions (allergic reactions) to anaphylaxis.
  • Candida infections of the mucous membrane, e.g. vaginal fungus and oral thrush
  • Skin rashes
  • Central nervous disorders such as headaches and dizziness

Depending on the active ingredients, numerous other side effects are possible, such as prolongation of the QT interval, psychiatric disorders, ototoxicity, liver dysfunction and renal dysfunction (selection). Bacteria can develop resistance to the agents due to selection pressure. As a result, antibiotics lose their effectiveness. Multi-resistant bacteria are resistant to multiple antibiotics.