3rd August 2023

Aminoglycosides

Mechanism of action

Like tetracyclines inhibit bacterial growth by binding to the 30s subunit of the bacterial ribosome, preventing the translation of RNA into proteins, but unlike tetracyclines, they are bactericidal, directly killing bacteria.

The mechanism of action is also concentration-dependent, meaning the higher doses of antibiotic given, the more effective against bacteria they are.

Spectrum of activity

Has some activity against Gram positive bacteria but is best known for its broad spectrum against Gram negative bacteria, and due to its effectiveness is generally used to treat severe infections. They are most effective against rapidly-multiplying bacteria, hence why they are effective in severe infections. However, they are not effective against anaerobes.

Examples include gentamicin (the most commonly used), tobramycin, amikacin, streptomycin and neomycin. Gentamicin, tobramycin, and amikacin also have activity against Pseudomonas aeruginosa. Aminoglycosides cannot be absorbed enterally and hence are generally given intravenously.

Important side effects, interactions and monitoring

Gentamicin generally has hospital-specific guidelines for administration and monitoring. It is increasingly given on a once-daily regime. Serum monitoring is essential to adjust the dose and avoid toxicity, especially in elderly patients or those with renal impairment.

The most important side effects of gentamicin to be aware of, is nephrotoxicity and ototoxicity, with the former necessitating regular monitoring of renal function.