Aminoglycosides antibiotics

1. Presented by:
Swornim Gyawali
Roll no :25
2010 batch

2. • Group of natural or semisynthetic antibiotics having
Glycosidic bond
Glycosidic bond
Polybasic amino group
Amino
sugar
Amino
sugar
Streptidine
2-deoxy streptamine
Garosamine

3. CLASSIFICATION
Systemic Topical
• Streptomycin Neomycin
• Gentamycin Framycetin
• Kanamycin
• Tobramycin
• Amikacin
• Sisomicin
• Netilmicin
Note:
 all derived from soil actinomycetes
 Not absorbed orally, excreted unchanged in urine
 Primarily active against aerobic gm –ve bacilli.

4. MECHANISM OF ACTION:
• Bactericidal antibiotics
• Two main steps:
a) Transport of the aminoglycosides through bacterial cell wall & cytoplasmic
membrane (diffusion-outer coat-Gm –ve via porin channel)
b) Irreversibly Binding to ribosomes (mostly 30s and 50s,30s &50s interface)
resulting in inhibition of protein synthesis.
Note : cidial action is concentration dependent i.e rate of bacterial cell killing is
directly realted to the ratio of peak antibiotic concn to the MIC value

5. THERAPEUTIC USES OF THE AMINOGLYCOSIDES
aminoglycosi
de
doses uses Active against
Streptomycin 1g or 0.75g i.m BD*7
TB : 1g 1/2 wkly
2months
TB,SABE, Urinary tract
infections, peritonitis,
septicemias
M.tuberculosis,brucell
a,yersinia
pestis,Calym.granulo
matis
Gentamicin 3-5mg/kg/day or
Divided in 3 doses 8
hrly
Respi infecion in
critically
ill,pseudomonas,proteu
s,meningitis,SABE
Ps.aeruginosa,proteu
s,e.coli,klebsiella
Tobramycin 3-5mg/kg/day in 1-3
doses
Gram negative infections,
Pseudomonas
Pseudomonas,
proteus
Amikacin 3-5mg/kg/day in 1-3
doses
Pseudomonas ,proteus
and staph. infections
Pseudomonas
,proteus and staph.
Neomycin 0.25-1g QID oral
0.3-0.5% topical
Infected
wounds,burns,ulcers,co
njunctivitis,external ear
Gm –ve bacilli and
some Gm+ve cocci

7. TOXICITY:
• Ototoxicity: concentrated in labrinthine fluid
• Nephrotoxicity : attain high concn. In renal cortex
• Neuromuscular blockage: reduce Ach release
• Contact dermatitis
Contraindication:
• Perforated ear drum
• Pregnancy :foetal toxicity
• Kidney damage person

8. TAKE HOME MESSAGE:
1. All are sulfate salts which are highly soluble in water and solutions
are stable for months
2. They ionize in solution, not absorbed orally, distribute only
extracellularly and do not penetrate in brain and CSF
3. All are excreted unchanged in urine
4. All are bactericidal and more active at alkaline pH
5. Act by interfering bacterial protein synthesis
6. Active against aerobic gm –ve bacteria, but spectrum differs
7. Partial cross resistance, organisms resistant to one amino glycoside
may still respond to another
8. Narrow margin of safety
9. All exhibit ototoxity and nephrotoxicity.