by Dr. Manura Nanayakkara

Created on: May 29, 2010   Last Updated: May 31, 2010

Aminoglycosides are a group of antibiotics that are used in serious infections as well as in topical infections. They include Gentamicin, Amikacin, Kanamycin, Neomycin, Paromomycin, Streptomycin, and Tobramycin. They are highly active against aerobic gram negative bacteria. Only intravenous forms and topical forms are available.

Mechanism of Action

These drugs are bactericidal in action. They inhibit protein synthesis of the bacteria by irreversibly binding to 30s ribosomal subunit of the susceptible bacteria.

Spectrum

Aminoglycosides are active against many gram negative aerobic bacteria and some gram positive aerobic bacteria. These drugs are active against tuberculosis causing mycobacteria as well (streptomycin has been dedicated for this purpose). They are not active against fungi or viruses.

What happened to the drug inside the body?

They are not absorbed by the gut. So only intravenous form is used in systemic infections. But neomycin is used to disinfect gut in liver failure. Excretion is principally via the kidneys. Accumulation inside the body occurs in kidney impairment.

Uses

Include severe bacterial endocarditis, Meningitis, Respiratory tract infections, severe urinary tract infections, and Tuberculosis.

Gentamicin

Gentamicin is the most widely used aminoglycoside. It has broad spectrum, but has poor activity against hemolytic streptococci and pneumococci.

Amikacin

Amikacin is more stable than gentamicin to bacterial enzyme inactivation. It can be used in gentamicin resistant infections.

Tobramycin

Tobramycin has similar activity to gentamicin. It is slightly more active against pseudomonas group of bacteria. It can even be administer by a nebulizer.

Neomycin

Neomycin is too toxic for systemic use. It is used only as topical preparations for skin infections and to reduce bacterial load during hepatic failure or before bowel surgery.

Side effects

Most side effects are dose related and include kidney damage and complete or partial deafness. They are common in elderly patients with kidney impairment. So doctors give aminoglycosides cautiously to patients with kidney diseases. Aminoglycosides impair neuromuscular transmission. Because of that it should not be given in myasthenia gravis patients.

They should not be combined with potentially ototoxic (Toxic to ears) diuretics.

Some serious sensitivity reactions like anaphylaxis are reported with aminoglycosides. If a patient is sensitive to one aminoglycoside, then possibilities are high that the patient is sensitive to other aminoglycosides as well.

Adverse Gastro intestinal effects such as nausea, vomiting, and diarrhea are common.

Pregnancy

Aminoglycosides can cause fetal harm when administered to pregnant women. So doctors give these drugs cautiously to pregnant women.

Fertility

Aminoglycosides do not reduce fertility.

Breast feeding

Small amount is present in breast milk. But it can be harmful. So doctors will not give them unless it is essential.

Sources

British National Formulary (www.bnf.org)

AHFS Drug Information

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