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

References
1.  https://medlineplus.gov/druginfo/meds/a682274.html
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4018441/
3. https://www.oregon.gov/oha/healthplan/EvidenceBasedReports/ps-2010-03-antibiotics-topical.pdf
4. Dermatologic Therapy, Vol. 25, 2012, 6–11. Update on Topical Antibiotics in Dermatology. http://apollohealing.com/wp-content/uploads/2015/07/Topical-Antibiotics-in-Dermatology-.pdf
5. Dermatology Pocket Guide: Application of Topical Product, Jabatan Farmasi Hospital Bukit Mertajam, First Edition 2016.
6. The Gulf Journal of Dermatology and Venereology, Volume 17, No.1, April 2010. Topical antibiotics in dermatology: An update http://apollohealing.com/wp-content/uploads/2015/07/Topical-Antibiotics-in-Dermatology-.pdf