Aminoglycosides

This group includes:

- Amikacin

- Kanamycin

- Gentamicin

- Neomycin

- Netilmicin

- Framycetin

- Tobramycin

- Streptomycin

- Spectinomycin

The aminoglycosides are active against aerobic Gram-negative bacilli, including pseudomonas. These antibiotics have no activity against anaerobes, and alone they are inactive against streptococci. When the aminoglycosides are used in combina­tion with penicillin or ampicillin, o synergistic effect is obtained against most streptococcal. including enterococci. Although the aminoglycosides are active against most staphylococci, they should not be considered first choice agents and should not be used alone to treat staphylococcal infections.

These agents are thus used in the treatment of serious infections with aerobic Gram-negative bacilli, including pseudomonas, complicated urinary tract infections, entero­coccal endocarditis (in combination with o penicillin). Amikacin can also be used in combination therapy in the treatment of resistant tuberculosis. Amikacin is particularly effective when used against bacteria that are resistant to other aminoglycosides, since its chemical structure makes it less susceptible to several inactivating enzymes. Depending on local patterns of resistance, amikacin may therefore be the preferred agent for serious infections caused by Gram-negative bacilli.

Streptomycin is now seldom used except in antituberculosis therapy, whereas specti­nomycin is used only to treat gonorrhoeae caused by penicillin-resistant gonococci.

The principal side effects of the aminoglycosides are otovestibular- and nephrotoxic­ity. They should be avoided when possible in the elderly and those with impaired renal function. Serum/plasma levels should be monitored in all patients receiving treatment for longer than 2 days. Once daily administration is as effective as divided doses and is the regimen of choice as the aminoglycosides' ability to kill microorganisms effectively is "concentration dependent".

These may be administered by the intravenous (IV) or intramuscular (IM) route. it should be noted that comparative studies have confirmed the efficacy of single daily dosage.

Iintramuscular (IM) administration: Standard IM injection technique

Predose (trough) level: Take serum (clotted blood) specimen within 15 minutes before the next dose.

Postdose (peak) level: Take serum (clotted blood) specimen l hour (60 minutes) after IM administration.

Intravenous (IV) administration: Bolus (IV"push") is not recommended. The preferred practice is to infuse the aminoglycoside in 5% dextrose or 0.9% NaCI over 15 to 30 min­utes.

Predose (trough) level: Take serum (clotted blood) specimen within 15 minutes before the next dose

Postdose (peak) level: Take serum (clotted blood) specimen 30 minutes after comple­tion of the rapid IV infusion.

Note: Once daily dosing of aminoglycosides makes monitoring of peak levels unnec­essary. The peak levels in the table refer to serum concentrations for 8 hourly dosing of gentamicin, netilmicin or tobramycin, and 12 hourly dosing of amikacin.