Polymyxins

Polymyxins is one of the first class of antibacterial medications which were synthesized at the beginning of 1940th years. They are characterized by a broad spectrum of antibacterial activity and high toxicity. Polymyxin B for parenteral use is considered to be reserve medication used for the treatment of pseudomonal infection. Previously Polymyxin was used orally for the treatment of intestinal infections. Currently, their use is limited, most commonly they are used in the form of local pharmaceutical forms.

Action mechanism.
Polymyxins exert bactericidal action which relates to interfering with the consistency of cytoplasmatic membrane in microbial cell.

Spectrum of activity
Polymyxins are active against gram-negative bacteria such as Shigella, Klebsiella, enterobacteria, Pseudomonas aeruginosa. Fusobacteria and bacteroides are moderately sensitive to Polymyxins.

Indications
Polymyxin B

  • Pseudomonal infections in case of resistance to penicillins, cephalosporins, aminoglycosides, fluoroquinolones
  • Severe gram-negative infection (except for proteus) caused by many resistant hospital strains
  • Bacterial eye infections (locally)
  • Otitis externa (locally)

Polymyxin M
Local treatment of Pseudomonas infections of infected wounds and burns.

Contraindications

  • Hypersensitivity to any of the medication ingredients
  • Renal failure
  • Myasthenia
  • Botulism
  • Pregnancy
  • Breastfeeding

Cautions
Pregnancy. Polymyxin B penetrates placenta and may exert toxic action on fetus.
Breastfeeding. The medication should be used with caution in breastfeeding mothers.
Geriatrics. The medication should be used with caution in this category of patients because of high risk of neurotoxicity and nephrotoxicity.
Urinary system. Polymyxin B is excreted by kidney in unchanged form therefore the dose should be corrected in patients with renal failure.

Side effects
Urinary system: nephrotoxicity that initially manifests in increased levels of creatinine and urea in the blood. Also the medication may cause severe proteinuria and hematuria

  • Nervous System: paresthesias, vertigo, weakness, peripheral neuropathy, confusion, hearing and mental disorders
  • Possible neuromuscular blockade with a threat of paralysis of respiratory muscles. The risk factors include renal failure, myasthenia gravis
  • Hematologic reactions: thrombocytopenia
  • Metabolic disorders: hypokalemia, hypocalcemia
  • Local reactions: pain and tissue damage in the injection site
  • Allergic reactions: rash, hives, bronchospasm, hypotension, collapse

Drugs interactions
Polymyxin B should not be combined with aminoglycosides and amphotericin b as well as muscle relaxants and anesthetics. This refers to Polymyxin B which is used in the form of eye and ear drops.

Information for patients
It is necessary to take the medication exactly as prescribed by your doctor. In case of application of ear drops it is necessary to warm the bottles in the arms. Consult your doctor if the symptoms do not improve within 7 days.

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