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Gentamicin C2.svg
Systematic (IUPAC) name
Clinical data
Trade names Genticyn, Garamycin, Magenta, Merigenta and others
AHFS/ monograph
MedlinePlus a682275
  • D
Legal status
Routes of
IV, eye drop, IM, topical
Pharmacokinetic data
Bioavailability limited oral bioavailability
Protein binding 0-10%
Biological half-life 2 hrs
Excretion renal
CAS Registry Number 1403-66-3 YesY
ATC code D06AX07 J01GB03 S01AA11 S02AA14 S03AA06 QA07AA91 QG01AA91 QG51AA04 QJ51GB03
PubChem CID: 3467
DrugBank DB00798 N
ChemSpider 390067 YesY
KEGG D08013 YesY
ChEBI CHEBI:27412 YesY
Chemical data
Formula C21H43N5O7
Molecular mass 477.596 g/mol
 N (what is this?)  (verify)

Gentamicin, sold under the brandname Garamycin among other, is an antibiotic used to treat many types of bacterial infections.[1] This may includes bone infections, endocarditis, pelvic inflammatory disease, meningitis, pneumonia, urinary tract infections, and sepsis among others. It is not effective for gonorrhea or chlamydia infections. It can be given intravenously, by injection into a muscle, or topically.[1] Topical formulations may be used in burns or for infections of the outside of the eye.[2] In the developed world it is often only used for two days until bacterial cultures determine what antibiotics the infection is sensitive to.[3] The dose required should be monitored by blood testing.[1]

Gentamicin can cause inner ear problems and kidney problems.[1] The inner ear problems can include problems with balance and problems with hearing. These problems may be permanent. If used during pregnancy it can cause harm to the baby.[1] It appears to be safe for use during breastfeeding.[4] Gentamicin is a type of aminoglycoside. It works by stopping the bacteria from making protein which typically kills the bacteria.[1]

Gentamicin was discovered in 1963.[5] It is made from the bacteria Micromonospora purpurea.[1] Gentamicin is on the World Health Organization's List of Essential Medicines, the most important medication needed in a basic health system.[6] It is available as a generic medication.[7] It wholesale cost is between 0.05 and 0.58 USD per day.[8]

Medical uses[edit]

Active against a wide range of bacterial infections, mostly Gram-negative bacteria including Pseudomonas, Proteus, Serratia, and the Gram-positive Staphylococcus.[9]

Gentamicin is not used for Neisseria gonorrhoeae, Neisseria meningitidis or Legionella pneumophila bacterial infections (because of the risk of the person going into shock from lipid A endotoxin found in certain Gram-negative organisms). Gentamicin is also useful against Yersinia pestis, its relatives, and Francisella tularensis (the organism responsible for tularemia seen often in hunters and/or trappers).[10]

Some Enterobacteriaceae, Pseudomonas spp., enterococci, Staphylococcus aureus and other staphylococci are resistant to gentamicin sulfate, to varying degrees.[11]

Side effects[edit]

Side effects of gentamicin toxicity vary between people. Side effects may become apparent shortly after or up to months after gentamicin is administered. Symptoms of gentamicin toxicity include:

  • Balance difficulty
  • Bouncing, unsteady vision
  • Ringing in the ears (tinnitus)
  • Difficulty multi-tasking, particularly when standing

Gentamicin is nephrotoxic. Risk factors for aminoglycoside nephrotoxicity include patient factors such as:

  • increased age
  • reduced renal function
  • pregnancy
  • hypothyroidism
  • hepatic dysfunction
  • volume depletion
  • metabolic acidosis
  • concurrent use of other drugs: vancomycin, NSAIDs, cisplatin, cyclosporin, cephalosporin, diuretics
  • Concurrent use of iodinated contrast agents

Treatment factors can also affect toxicity. Important factors such as dose, frequency, levels and duration of therapy can affect level of toxicity.

Psychiatric symptoms related to gentamicin can occur. These include anorexia, confusion, depression, disorientation and visual hallucinations.[12]

A number of factors and determinants should be taken into account when using gentamicin, including differentiation between empirical and directed therapy which will affect dosage and treatment period.[3] Many medical practitioners freely administer gentamicin as an antibiotic without advising people of the severe and permanent potential ramifications of its use. Gentamicin is well known to be a cheap, low-cost yet old medicine when compared with alternatives, and is typically US$3–6 per dosage less than alternatives.

Inner ear[edit]

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, usually if taken at high doses or for prolonged periods of time, but there are well documented cases in which gentamicin completely destroyed the vestibular apparatus after three to five days.[citation needed] A small number of affected individuals have a normally harmless mutation in their mitochondrial DNA encoding the 12S ribosomal RNA (m.1555 A>G), that allows the gentamicin to affect their cells.[13] The cells of the ear are particularly sensitive to this, sometimes causing complete hearing loss.[14] However, gentamicin is sometimes used intentionally for this purpose in severe Ménière's disease, to disable the vestibular apparatus. These side effects are most common when the drug is administered via drops directly to the ear.


Prevention of nephrotoxicity includes judicious use of IV fluids to correct and avoid volume depletion, correction of hypokalemia and hypomagnesemia. Once daily dosing has been shown to be less toxic than multiple daily doses. Gentamicin is usually dosed by ideal body weight. Various formulae exist for calculating gentamicin dosage. Trough and peak serum levels of gentamicin are monitored during treatment to individualize therapy and prevent excess exposure.[15]

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.[16]

Mechanism of action[edit]

Gentamicin is a bactericidal antibiotic that works by irreversibly binding the 30S subunit of the bacterial ribosome, interrupting protein synthesis. This mechanism of action is similar to other aminoglycosides[17] Gentamicin is a bactericidal antibiotic.


Gentamicin is composed of a number of related gentamicin components and fractions which have varying degrees of antimicrobial potency.[18] The main components of gentamicin include members of the gentamicin C complex: gentamicin C1, gentamicin C1a, and gentamicin C2 which compose approximately 80% of gentamicin and have been found to have the highest antibacterial activity. Gentamicin A, B, X, and a few others make up the remaining 20% of gentamicin and have lower antibiotic activity than the gentamicin C complex.[19] The exact composition of a given sample or lot of gentamicin is not well defined, and the level of gentamicin C components or other components in gentamicin may differ from lot-to-lot depending on the gentamicin manufacturer or manufacturing process. Because of this lot-to-lot variability, it can be difficult to study various properties of gentamicin including pharmacokinetics and microorganism susceptibility if there is an unknown combination of chemically related but different compounds.[20]


Gentamicin for injection

Gentamicin is produced by the fermentation of Micromonospora purpurea. It was discovered in 1963 by Weinstein, Wagman et al. at Schering Corporation in Bloomfield, N.J. working with source material (soil samples) provided by Rico Woyciesjes.[21] Subsequently it was purified and the structures of its three components determined by Cooper, et al., also at the Schering Corporation. It was initially used as a topical treatment for burns at the Atlanta and San Antonio burn units and was introduced into IV usage in 1971. It remains a mainstay for use in sepsis.

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) generally have their spellings ending in ~micin and not in ~mycin.


Gentamicin is also used in molecular biology research as an antibacterial agent in tissue and cell culture, to prevent contamination of sterile cultures. Gentamicin is one of the few heat-stable antibiotics that remain active even after autoclaving, which makes it particularly useful in the preparation of some microbiological growth media.


  1. ^ a b c d e f g "Gentamicin Sulfate". The American Society of Health-System Pharmacists. Retrieved Aug 15, 2015. 
  2. ^ Bartlett, Jimmy (2013). Clinical Ocular Pharmacology (s ed.). Elsevier. p. 214. ISBN 9781483193915. 
  3. ^ a b Moulds, Robert and Jeyasingham, Melanie (October 2010). "Gentamicin: a great way to start". Australian Prescriber (33): 134–135. 
  4. ^ "Gentamicin use while Breastfeeding". Retrieved 15 August 2015. 
  5. ^ Pucci, edited by Thomas Dougherty, Michael J.; Weinstein, Marvin J. (2011). Handbook of antibiotic discovery and development (2012 ed.). New York: Springer. p. 238. ISBN 9781461413998. 
  6. ^ "WHO Model List of EssentialMedicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014. 
  7. ^ Burchum, Jacqueline (2014). Lehne's Pharmacology for Nursing Care. Elsevier Health Sciences. p. 1051. ISBN 9780323340267. 
  8. ^ "Gentamicin Sulfate". International Drug Price Indicator Guide. Retrieved 15 August 2015. 
  9. ^ Gentamicin: Drug Information Provided by Lexi-Comp: Merck Manual Professional
  10. ^ Goljan, Edward F. (2011). Rapid Review Pathology 3rd ed. Philadelphia, PA: Elsevier. p. 241. ISBN 978-0-323-08438-3. 
  11. ^ "Gentamicin spectrum of bacterial susceptibility and Resistance" (PDF). Retrieved 15 May 2012. 
  12. ^ AJ Giannini, HR Black. Psychiatric, Psychogenic and Somatopsychic Disorders Handbook. Garden City, NY. Medical Examination Publishing Co.,1978. Pp.136-137. ISBN 0-87488-596-5.
  13. ^ Pandya, A (1993). Pagon, R. A.; Adam, M. P.; Ardinger, H. H.; Bird, T. D.; Dolan, C. R.; Fong, C. T.; Smith, R. J. H.; Stephens, K, eds. "Nonsyndromic Hearing Loss and Deafness, Mitochondrial". PMID 20301595. 
  14. ^ Gentamicin Toxicity at the American Hearing Research Foundation
  15. ^ Lopez-Novoa, Jose (2011). "New insights into the mechanism of aminoglycoside nephrotoxicity: an integrative point of view.". Kidney International 79: 33–45. doi:10.1038/ki.2010.337. PMID 20861826. Retrieved 2014-09-30. 
  16. ^ Sundin DP, Sandoval R, Molitoris BA: Gentamicin Inhibits Renal Protein and Phospholipid Metabolism in Rats: Implications Involving Intracellular Trafficking. J Am Soc Nephrol 12:114-123, 2001
  17. ^
  18. ^ Weinstein, Marvin J. "Biological Activity of the Antibiotic Components of the Gentamicin Complex." Journal of Bacteriology 94.3 (1967): 789-90. Web. 15 Oct. 2013.
  19. ^ Vydrin, A. F. "Component Composition of Gentamicin Sulfate Preparations." Pharmaceutical Chemistry Journal 37.8 (2003): 448-49. Web. 15 Oct. 2013.
  20. ^ Isoherranen, Nina, and Eran Lavy. "Pharmacokinetics of Gentamicin C1, C1a, and C2 in Beagles after a Single Intravenous Dose." Antimicrobial Agents and Chemotherapy 44.6 (2000): 1443-447. Web.
  21. ^ Weinstein, Marvin; Wagman (1963). "Gentamicin, A New Antimicrobial Complex from Micromonospora". J Med Chem 6: 463–464. doi:10.1021/jm00340a034.