Gentamicin

A bactericidal, easily water-soluble antibiotic complex from the group of aminoglycosides, extracted from cultures of Micromonospora purpurea and M. echinospora. Gentamicin is used as a sulphate salt for bacterial infections. The active ingredient contains several very similar fractions C1 (25-35%), C1a (20-31%) and C2 (40-45%).

The basic structure of all aminoglycosides consists of a central hexose core, which is glycosidically linked to 2 amino sugars. Aminoglycosides carry free OH and NH2 groups: the OH groups make the mixture hydrophilic. The NH2 groups give the mixture slightly basic and nucleophilic properties in neutral and alkaline environments.

Gentamicin has a bactericidal effect by binding to the 30s subunit of the bacterial ribosome, preventing the reading of mRNA and thus inhibiting protein biosynthesis. In high doses gentamicin has a cytotoxic effect.

Gentamicin is mainly effective against Gram-negative bacteria, including problem germs. Gentamicin is used against the following germs: Staphylococci, Enterobacter aerogens, Pseudomonas aeruginosa, Haemophilus influenzae, Escherichia coli, Proteus mirabilis, Klebsiella, Gonococci, Salmonella.

Systemic use: Gentamicin has a relatively narrow therapeutic range.

Topical applications: Gentamicin-containing topicals are offered in ophthalmology and dermatology. Its use in wound treatment no longer appears to be necessary as there is a strong problem of resistance.

Gentamicin is used as an implantable chain (Septopal®) in infected bones and soft tissue. It is also used as a component of bone cement in joint implants.

Indications are severe and most severe infections that cannot be controlled by other (better tolerated antibiotics), e.g.:

Severe respiratory tract, urinary tract and soft tissue infections; severe intra-abdominal infections, sepsis, meningitis, endocarditis, infections of the eye with threatening ophthalmia.

Gentamicin should always be used in combination with a betalactam antibiotic (e.g. piperacillin). A combination with ampicillin is considered the standard therapy for listeria meningitis.

• Systemic: The initial dose in adults is 120 mg or 1.5-2 mg/kgkgKG, regardless of kidney function. Maintenance dose: 1-2mg/kgkgkgkg every 8h. In case of renal insufficiency the dose is reduced accordingly.
• Topical skin: Cream/powder (0.1-0.2%): Apply thinly 2-3 times/day in the area of the affected skin areas.
• Topical conjunctiva: Eye drops/ointment (0.5%): Apply 1 trp. 4-6 times/day or 0.5-1 cm ointment into the conjunctival sac.

Remember! Topical application only if there is no therapeutic alternative! Max. Therapy duration: 14 days.

Topical application: Irritations, sensitization.

Systemic: Gentamicin is ototoxic (in 1-3 % of cases) and nephrotoxic. In the inner ear, depending on the concentration, it can lead to balance disorders (up to 14 %) and hearing loss.

The multi-organ toxicity limits the use of this antibiotic to severe, mostly nosocomial infections. Serum levels should be monitored (max. 15-20 mg/l), especially in problem cases (e.g. in newborns).

Gentamicin cream 0,1%

If aminoglycoside antibiotics are obtained from Streptomyces species, a "y" is inserted in the name extension (-ycin). If aminoglycoside antibiotics are obtained from Micromonospora species, an "i" is inserted in the suffix (-icin) (gentamicin)

1. Baltch AL et al (2007) Antimicrobial Activities of Daptomycin, Vancomycin, and Oxacillin in Human Monocytes and of Daptomycin in Combination with Gentamicin and/or Rifampin in Human Monocytes and in Broth against Staphylococcus aureus. Antimicrobial agents Chemother 51: 1559-1562