Thursday, June 15, 2017

Neomycin vs Gentamicin : Topical

General principle

  • Aminoglycosides are effective against aerobic gram negative and some gram positive bacteria. Its mechanism of action is to inhibit protein synthesis by binding with ribosomal RNA, causing      misreading of the bacterial genetic code thus slow down the growth of microorganism.
  • The differences in susceptibility/resistance are subtle and related to resistance producing enzymes.
  • All aminoglycosides can cause nephrotoxicity, ototoxicity and vestibular toxicity. They also share toxicities like skeletal muscle paralysis and cardiac muscle weakness
Gentamicin
  • A product of a strain of Micromonospora purpurea.
  • Based on The Gulf Journal of Dermatology and Venereology , it has a similar “spectrum” to related antibiotics such as neomycin, but a rather greater activity than these against some species of bacteria
  • Almost all enterobacteria are sensitive to it, including species of Aerobacter, Escherichia, Klebsiella, Salmonella, Shigella, Proteus, and Pseudomonas
  •  Advantage : A high degree of activity against Pseudomonas aeruginosa
  • Most sensitive gram positive organism:  Staphylococci
  • It is bactericidal in concentrations little greater than those inhibiting growth
Neomycin
  • Neomycin sulfate is the sulfate salt of neomycin B and C
  • Produced by the growth of Streptomyces fradiae
  • With the exception of P. aeruginosa, it is bactericidal against most gram 
  • negative bacteria; however, it lacks activity against anaerobes
  • It is active against some gram-positive bacteria, including staphylococci, but is not effective against streptococc
  • Frequently combined with other topical antimicrobials to improve its coverage against gram-positive bacteria


Topical Antibiotic
Gentamicin
Neomycin
Indication        
     - Treatment of burns
     - Bedsore
     - Impetigo
     - Folliculitis
     - Nasal carriers of staphylococci
     - Any other localized infection
     -  Adjunctive treatment of    burns 
     - Superficial infection
     - Prophylaxis against infection  in minor wounds and postoperative wound
     - Superinfection in chronic  dermatoses
Sensitive organism
Gram Negative (-)
- Almost all enterobacteria –  (Aerobacter, Escherichia,   
  Klebsiella,Salmonella,    Shigella, Proteus and Pseudomonas)
- A high degree of activity against Pseudomonas Aeruginosa
Gram positive (+)
Most sensitive: Staphylococci
Moderate sensitive: Streptococci 
  (except S. faecalis) & Pneumococci 
Gram negative (-)
Bactericidal against most 
  gram negative bacteria
- Lack of activity against 
  anaerobes.
Gram positive (+)
     - Active against some gram- positive bacteria, including Staphylococci
      - Not effective against Streptococci
Formulation
      Gentamicin 0.1% cream
            Gentamicin 0.1%ointment
     Neomycin0.5% Cream 
     Neomycin 0.5% Ointment
Availability in Hospital Keningau
      Unavailable (alternatively can use     Gentamicin 0.3% eye ointment)

      Neomycin 0.5% Cream

Dosage/Application
Adult & child > 1 year : Apply to affected skin 2 times daily
Apply sparingly to affected area up to 2 times daily (for short term us, 1-2 weeks)
Others
Side effect:
Redness, itchiness, swelling
Special precaution: Avoid prolonged use
Side effect:
Skin sensitization or contact dermatitis. The sensitivity disappears once treatment is discontinued

Special precaution:
Super infection can may occur on prolonged use


Conclusion

  • In fact, gentamicin and neomycin are aminoglycosides that demonstrate the same mechanism of action in inhibiting protein synthesis by binding with ribosomal RNA thus slowing the bacteria growth

  • The advantage of gentamicin over neomycin is, its broad spectrum activity and the ability to cover Pseudomonas Aeruginosa-caused infection while neomycin is unable to cover it 

  • Nevertheless, both neomycin and gentamicin still have the same bactericidal mechanism even to different organisms and due to that similar characteristic, they can be used interchangeably to treat skin infections






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