Aminoglycosides typically have a suffix ending with “-mycin”, except for Amikacin which ends in “cin”. The most common drugs can be remembered by the acronym “GNATS,” which represents Gentamicin, Neomycin, Amikacin, Tobramycin and Streptomycin.
Gentamicin is used for gram negative infections such as Pseudomonas aeruginosa and Proteus mirabilis, but isn't used for Neisseria or Legionella. Its clinical use is limited due to its side effects of ototoxicity and nephrotoxicity, and it cannot be given orally due to its lack of small intestinal absorption. Combined with vancomycin or a beta-lactam antibiotic, gentamicin can be used to treat serious infections caused by gram positive cocci (Staphylococcus aureus, Enterococcus, and some streptococci).
Neomycin is a popular topical aminoglycoside for eye, ear, and skin infections. It is not used as a systemic treatment, as it is highly ototoxic and nephrotoxic. It is used to reduce the risk of infection during intestinal surgery by eliminating intestinal bacteria.
This aminoglycoside is used for Pseudomonas, Enterobacter and Serratia infections. Like other drugs in its class, it can lead to nephrotoxicity and ototoxicity, so patients should be carefully monitored if they have renal disease.
Tobramycin is used for gram negative infections. It has slightly better coverage than gentamicin when treating pseudomonal infections of the lungs. It cannot be given orally, but has use in ophthalmic infections for bacterial conjunctivitis (Tobrex). This drug leads to nephrotoxicity and ototoxicity.
Streptomycin was the first aminoglycoside discovered, and has use for mycobacterium tuberculosis infections and Yersinia pestis. This drug has the side effects of nephrotoxicity and ototoxicity.
Unlike bacteriostatic agents, which simply stop bacteria from reproducing, bactericidal agents actually cause bacterial cell death. They work by inhibiting synthesis of proteins and bacterial enzymes used for DNA replication and cell division. The lack of bacterial enzymes leads to breaks in the DNA, killing the bacteria directly. A higher concentration of medication leads to quicker eradication of the infection.
Aminoglycosides are typically used for the treatment of serious infections due to aerobic gram negative bacilli. The most frequent use of these antibiotics include empiric therapy for serious infections including septicemia, complicated intraabdominal infections, UTIs, and nosocomial URIs.
The aminoglycoside Neomycin is often used for bowel surgery prep to suppress bowel flora and decrease the risk of infection after surgery. Remember, aminoglycosides are not absorbed well into body through the GI tract, so the risk of side effects is much lower when using it for bowel surgery preparation.
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