lecture on aminoglycosides

1. AMINOGLYCOSIDES
- DR. JERIN

2. Aminoglycosides
Aerobic, gram
negative bacilli
E.Coli, Salmonella,
Shigella
V.cholerae,
Pseudomonas
Streptomycin
Gentamicin
Amikacin
Kanamycin
Tobramycin
NeomycinOtotoxicity
Nephrotoxicity30s ribosomes
Bactericidal
Not absorbed
orally

3. INTRODUCTION
• Antibiotics of amino sugars joined by glycosidic linkages
• 2 types based on the source
• Soil actinomycetes
Genus Streptomyces
Streptomycin
Kanamycin
Tobramycin
Neomycin
Genus Micromonospora
Gentamicin
Netilmicin
Amikacin

4. ANTIBACTERIAL SPECTRUM :
• Narrow spectrum
• Aerobic gram negative bacilli
• E.coli
• Salmonella
• Shigella
• V. cholerae
• klebsiella

5. MECHANISM OF ACTION :
Penetrates the bacterial cell membrane through
aqueous pores
Reaches the periplasmic
spaces
Binds to 30s
ribosomes
Block initiation of protein
synthesis
Cause misreading of
mRNA & terminate
protein synthesis
Addition of
incorrect amino
acids
Inhibition of protein synthesis
BACTERICIDAL
EFFECT

6. RESISTANCE :
• Aminoglycoside inactivating enzyme
• Low affinity of ribosomes
• Decrease in permeability

7. Pharmacokinetics :
• Not absorbed from GIT
• Peak level is seen in 60min following IM administration
• Excreted through kidneys
• T
𝟏
𝟐
is 2-3hrs.

8. Adverse Effects :
• Ototoxicity :
 Both vestibular & auditory dysfunction
 The drug concentrates on the labyrinthine fluid of the inner ear & damages both
the cochlear hair cells & vestibular sensory cells
 Causes progressive & permanent deafness
 Vestibular symptoms : headache, nausea, vomiting, dizziness, vertigo, nystagmus,
ataxia
 Neomycin, Amikacin, Kanamycin – deafness
 Streptomycin, Gentamicin – vestibular toxicity
• Nephrotoxicity :
 Drug attains high concentration in the renal cortex & damages renal tubules
 These effects are reversible.
 Gentamicin, Neomycin, Tobramycin – Nephrotoxic
• Neuromuscular blockade
 Curare like effect.

9. Uses :
• Infections of gram negative bacteria
• Streptococcal & enterococcal endocarditis along with penicillin
• Tuberculosis – streptomycin, kanamycin, amikacin

10. Streptomycin :
• Least nephrotoxic among aminoglycosides.
• Uses :
• Tuberculosis
• Subacute bacterial endocarditis : along with
penicillin
• Plague, tularaemia & brucellosis : along with
tetracycline

11. Gentamicin :
• More potent & broader spectrum of action
• More nephrotoxic & vestibulotoxic
• Uses :
• UTI
• Pneumonia
• Meningitis
• SBE
• Topical : cream for burns & infected wounds.

12. Amikacin :
• Semisynthetic derivative
• Widest antibacterial spectrum
• RESISTANT TO AMINOGLYCOSIDE INACTIVATING ENZYME
• Uses :
• Nosocomial infection
• Tuberculosis

13. Neomycin :
• Both gram positive & negative spectrum
• Highly ototoxic
• Not given systemically
• Used topically
• Also used orally for action on gut

14. Thank you …