Aminoglycosides

WIKIDRUGS ANTIBIOTICS

This is a large group of antibiotics that are made up of a sugar group and an amino group. As this is a large and diverse group we shall firstly discuss general characteristics and then one by one go through each drug to show and explain their differences.

General Group Characteristics

Mechanism of Action

The drug must first enter the bacterial cell which it does via a oxygen-dependent active transport system. Thus it is unable to work against any anaerobic species. Once inside the cell it disrupts protein synthesis by acting directly on the ribosome. Unlike the other antibiotics that act at the level of protein synthesis these drugs are bactericidal and are concentration dependent killers. They will act synergistically with any antibiotic that disrupts cell wall synthesis, ie any of the beta-lactams.

Spectrum of Activity

• They are active mainly against gram-negative species, including some of the hardier species.
• They are inactive against anaerobes, this is because their action is dependent on oxygen-dependent active transport systems.
• They tend not to work well in purulent material.
• If the local tissue environment is acidic the efficacy of the drug will be reduced.

Pharmacokinetic Considerations

Aminoglycosides: Very hydrophilic molecules, weak bases. • Not absorbed from GI tract.

• Distribute poorly (confined to extracellualr fluid mostly – volume of distribution 0.2 l/kg).

• Renally excreted – accumulate in proximal tubular cells