1. Administration:

The highly polar, polycationic structure of the aminoglycosides prevents adequate absorption after oral administration Therefore, all aminoglycosides (except neomycin must be given parenterally to achieve adequate serum levels. [Note: The severe nephrotoxicity associated with neomycin precludes parenteral administration, and its current use is limited to topical application for skin infections or oral administration to prepare the bowel prior to surgery.] The bactericidal effect of aminoglycosides is concentration and time dependent They also have a postantibiotic effect. Because of these properties, once daily dosing with the aminoglycosides can be employed. This results in less toxicity, and is less expensive to administer. The exceptions are pregnancy, neonatal infections, and bacterial endocarditis, in which these agents are administered in divided doses every 8 hours. [Note: The dose that is administered is calculated based on lean body mass, because these drugs do not distribute into fat.]