Ampicillin belongs to the group of beta-lactam antibiotics. In terms of structure and action, it is classified as a semi-synthetic penicillin with an extended range of action. In which conditions is ampicillin used? What are the possible side effects of its use?

Action and indications for the use of ampicillin

The general mechanism of action of beta-lactam antibiotics is based on the presence of a beta-lactam ring in their molecule. Bacteria have a penicillin binding protein (PBP) in their structure, which binds to the beta-lactam ring, blocking the activity of bacterial cytoplasmic membrane transpeptidases and inhibiting the synthesis of peptidoglycan, necessary for the synthesis of the correct structure of the bacterial cell wall. By blocking the biosynthesis of the bacterial cell wall, the bacteria die.

The scope of action of ampicillin includes:

  • benzylpenicillin-sensitive bacteria,
  • Salmonella spp.,
  • Shigella spp.,
  • Escherichia coli,
  • Haemophilus influenzae,
  • Bordetella pertussis (Haemophilus pertussis),
  • Proteus mirabilis.

Ampicillin can be used both orally and intravenously, and the indications for its use include the treatment of such conditions as:

  • acute paranasal sinusitis and otitis media,
  • streptococcal pharyngitis,
  • community acquired pneumonia,
  • COPD exacerbation,
  • urinary tract infection caused by enterococci,
  • eradication of H. pylori,
  • endocarditis,
  • meningitis.

Bacterial resistance mechanisms

Bacteria have developed various mechanisms of resistance to antibiotics from the beta-lactam group. We can distinguish:

  • PBP receptor resistance(change of PBP structure, synthesis of new structured PBP, no PBP).
  • G (-) bacteria may havetransport resistancenatural (no possibility to cross the outer membrane e.g. by particle size) or acquired (after the first contact - P. aeruginosa)
  • Enzymatic resistance- production of beta-lactamases:
    • G + bacteria → secretion of beta-lactamases outside the cell
    • G- bacteria → trapped inperiplasmic space, do not pass through the outer membrane. They can be constitutively encoded (constant level regardless of the presence of an antibiotic - natural immunity) or induced (synthesis takes place in the presence of beta-lactam, induction depends on the type of compound and is temporary or permanent
    • Penicillinases and cephalosporinases are broad-spectrum beta-lactamases
  • Efflux- active antibiotic removal via pump systems

Enzymatic resistance can be inhibited by the use of beta-lactamase inhibitors such as:

  • clavulanic acid,
  • sulbaktam
  • or tazobaktam.

Aminopenicillins are usually found in combination with clavulanic acid.

Ampicillin dosage

Ampicillin dosage depends on the type of microorganism causing the infection, the susceptibility of the microorganism to ampicillin, the severity and location of the infection.

The amount of aminopenicillin dose will also depend on the route of administration and the age and weight of the patient.

Precautions and contraindications for ampicillin use

Be especially careful in the case of:

  • renal failure (creatinine clearance control and possibly dose reduction necessary),
  • hypersensitivity and anaphylaxis reactions to penicillin drugs,
  • suspected infectious mononucleosis,
  • pregnancy and breastfeeding (use only if the doctor deems it absolutely necessary).

Prolonged or unjustified use of ampicillin is not recommended due to increased bacterial resistance to this antibiotic and the formation of insensitive strains.

Patients using oral anticoagulants should pay special attention to the prothrombin time when using ampicillin, as the dose of the anticoagulant may need to be changed.

Ampicillin and probenecid should not be used simultaneously, and in the case of methotrexate, care should be taken to increase the risk of its toxicity.

Side effects of ampicillin

The most common side effects associated with the use of ampicillin include:

  • candidiasis of the skin and mucous membranes,
  • nausea,
  • vomiting,
  • dizziness,
  • headache,
  • diarrhea,
  • disorders of the blood and lymphatic system.

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