Gentamicin

Systematic (IUPAC) name
2-[4,6-diamino-3- [3-amino-6-(1-methylaminoethyl) tetrahydropyran-2-yl] oxy-2-hydroxy- cyclohexoxy]-5-methyl- 4-methylamino-tetrahydropyran-3,5-dio

Excretion renal
Half life 2 hours
Routes IV/IM
Protein binding 0-10%
Bioavailability limited oral bioavailability
FormulaC21H43N5O7
Mol. mass 477.596 g/mol



Molecular model showing how Gentamicin binds to bacterial DNA
Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative bacteria. However, gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila bacterial infections.
It is synthesized by Micromonospora, a genus of Gram-positive bacteria widely present in the environment (water and soil). To highlight their specific biological origins, gentamicin and other related antibiotics produced by this genus (verdamicin, mutamicin, sisomicin, netilmicin, retymicin) have generally their spellings ending in ~micin and not in ~mycin. Gentamicin is a bactericidal antibiotic that works by binding the 50S subunit of the bacterial ribosome, interrupting protein synthesis.


Like all aminoglycosides, when gentamicin is given orally, it is not systemically active. This is because it is not absorbed to any appreciable extent from the small intestine. It appears to be completely eliminated unchanged in the urine. Urine must be collected for many days to recover all of a given dose because the drug binds avidly to certain tissues. It is administered intravenously, intramuscularly or topically to treat infections.

E. coli has shown some resistance to gentamicin, despite being Gram-negative. Gentamicin is one of the few heat-stable antibiotics that remain active even after autoclaving, which makes it particularly useful in the preparation of certain microbiological growth media.Treatment of susceptible bacterial infections, normally Gram-negative bacteria including Pseudomonas, Proteus, Serratia, and Gram-positive Staphylococcus.

Side effects
All aminoglycosides are toxic to the sensory cells of the ear, but they vary greatly in their relative effects on hearing versus balance. Gentamicin is a vestibulotoxin, and can cause permanent loss of equilibrioception, caused by damage to the vestibular apparatus of the inner ear if taken at high doses or for prolonged periods of time. Gentamicin has on occasion impaired or even wholly destroyed hearing. In most instances, the affected individual has undergone treatment for 2 weeks or more. A small number of affected individuals have a normally harmless mutation in their mitochondrial RNA, that allows the gentamicin to affect their cells. The cells of the ear are particularly sensitive to this. Gentamicin is sometimes used intentionally for this purpose in severe Ménière's disease, to disable the vestibular apparatus.
Gentamicin can also be highly nephrotoxic, particularly if multiple doses accumulate over a course of treatment. For this reason gentamicin is usually dosed by body weight. Various formulae exist for calculating gentamicin dosage. Also trough and peak serum levels of gentamicin are monitored during treatment, generally before and after the third dose is infused. Gentamicin, like other aminoglycosides, causes nephrotoxicity by inhibiting protein synthesis in renal cells. This mechanism specifically causes necrosis of cells in the proximal tubule, resulting in acute tubular necrosis which can lead to acute renal failure.
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