Polymixins

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Polymixin B
  • Polymixins (polymixin E): basic peptides which are amphipathic (containing lipophilic and lipophobic groups).
  • Active against gram-negative bacteria.
  • Bacteriocidal for many gram-negative rods including Pseudomonas.
  • Disrupt bacterial cell membranes through strong interactions with phospholipid components.
  • Gram-positive bacteria, Proteus, Neisseria are resistant to polymixins.
  • Polymixin B sulfate used topically for treatment of external otitis and corneal ulcers due to Pseudomonas aeruginosa.
  •  Systemic use of polymixins not recommended becasue of poor tissue distribution, significant nephrotoxicity and neurotoxicity and the availability of more effective other antibacterial drugs.
Polymixin E: Active Against:
  • Pseudomonas aeruginosa
  • Escherichia coli

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  • Enterobacter
  • Klebsiella
Chambers, H.F.and Hadley, W. K. Micellaneous Antimicrobial Agents: Disinfectants, Antiseptics adn Sterilants, in Basic and Clinical Pharmacology,(Katzung, B. G., ed) Appleton-Lange, 1998, pp 803-804.
Robertson, D.B, and Maibach, H.I. Dermatologic Pharmacology , in Basic and Clinical Pharmacology,(Katzung, B. G., ed) Appleton-Lange, 1998, p 1000.
Kapusnik-Uner, J.E., Sande, M.A. and Chambers,J.F. Antimicrobial agents: Tetracyclines, Chloramphenicol, Erythromycine, and Miscellaneous Antibacterial Agents, In, Goodman and Gillman's The Pharmacologial Basis of Therapeutics,(Hardman, J.G, Limbird, L.E, Molinoff, P.B., Ruddon, R.W, and Gilman, A.G.,eds) The McGraw-Hill Companies, Inc.,1996, pp.1143-1144.
Gramicidin
  •  Gramicidin: peptide antibiotic which alters membrane permeability-effective against gram-positive organisms
  • Gramicidin may be used in combination with neomycin, polymyxin B or both.
  • Available only for topical usage
  •  Systemic toxicity
Gramicidin Active Against:
  • Streptococci
  • Pneumococci
  • Staphylococci
  • Most anaerobic cocci

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  • Neisseriae
  • tetanus bacilli
  • diphtheria bacilli
Robertson, D.B, and Maibach, H.I. Dermatologic Pharmacology , in Basic and Clinical Pharmacology,(Katzung, B. G., ed) Appleton-Lange, 1998, p 1000.

 

Clinical Applications of Polymixin B
  • Skin, mucous membrane, eye and ear infections (for sensitive organism).
  • For example, external otitis (Pseudomonas) or corneal ulcers (Pseudomonas aeruginosa
  • Sometimes used by aerosol as an adjunct to other antibiotics in difficult cases of Pseudomonas pneumonia.

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