Aminoglycosides

Aminoglycosides: It is a group of drugs that contain two or more amino sugar joined through glycosidic linkagevto the central Hexose nucleus.

Name the aminoglycoside antibiotics:

1)      Streptomycin.

2)      Neomycin.

3)      Kanamycin.

4)      Gentamicin.

5)      Tobramycin(best for pseudomonas).

6)      Amikacin.

7)      Netilmicin.

8)      Sisomicin.

All aminoglycosides are given by injection expect Neomycin.

Common properties:

[A]Physical & chemical properties:

1)      They have a hexose ring to which 2 or more amino sugars are attached by glycosidic linkage.

2)      They are more water soluble,less lipid soluble.

3)      They are highly polycataonic drugs(+ve change)

4)      They are more active in alkaline pH(extracellular pH).

[B]Pharmacokinetic properties:

1)      Absorption:Poorly absorbed from GIT.Usually administered IV or IM.

2)      Distribution:Limited distribution,mostly extracellularly.They are highly concentrated to renal cortex.

3)      Metabolism:They are not metabolized in the body.

4)      Excretion:By kidney(through glomerulus)

5)      Plasma :2-3 hours.

[C] Pharmacodynamic properties:

1)      Bactericidal,Pus has to be removed for the action of aminoglycosides because pus area is oxygen less and aminoglycosides require Oxygen for their action.

2)      Combine with 30 s ribosomol subunit of bacteria.

[D]Resistant properties:Micro-organisms usually develop resistance against theses drugs.

[E]Adverse effects:Low theraputic index-Less safe and exhibit common toxic effects:

a)      Ototoxicity.

b)      Nephrotoxicity.

c)       Myotoxicity.

[F]Clinical use:

1)      Local use-as gut sterilizer.

2)      Mostly used against gram negative entric bacteria.

3)      They are almost always used in combination with a beta-lactum antibiotic in order to extend coverage.  

                     (Ref: Katzung-11th,P-807-810)

Pharmacological effects:

[A]Bactericidal.

[B] Adverse effects:They exhibit common toxic effects:

·         Ototoxicity.

·         Nephrotoxicity.

·         Myotoxicity.

Indication of Amynoglycoside/Streptomycin:

1)      UTI.

2)      TB(Steptomycin).

3)      Bacillary dysentery.

4)      Enterobacteriaceae infection.

5)      Abdominal infection.

6)      Pelvic sepsis.

7)      Septiecmia.

8)      Plague(steptomycin).

9)      Brucellosis(steptomycin).