No absorption is possible when an aminoglycoside is ingested orally, but of course, an oral aminoglycoside exists, just like oral vancomycin, because you don’t care for it to get into the blood because you want it to work in the GI tract anyway. This is useful for pre-operative bowel sterilization: two antibiotics are given the day before surgery: Neomycin with erythromycin.
This is another drug class where we must monitor the peak and trough levels just like with vancomycin to make sure we don’t develop ototoxicity and nephrotoxicity.
Aminoglycoside examples (injectables):
- Amikacin (Amikin)
- Gentamicin (Garamycin)
- Tobramycin (Nebcin)
- Neomycin
When we deal with intravenous aminoglycosides, we’re usually using gentamicin. Some hospitals say we can’t use tobramycin and amikacin unless there’s resistance to gentamicin. We don’t want to overuse these to not create resistance. However, if it’s a nosocomial infection, you could automatically assume it’s a resistant organism and go straight to using tobramycin/amikacin.
Neomicin is found in an ointment that’s very well known with all of you: Triple antibiotic ointment called Neosporin. It has 3 antibiotics in it, neomycin, bacitracin and polymyxin B.
We could also use amonglycosides for eye and ear infections as drops.
Recap
- No oral absorption
- Nephrotoxic and Ototoxic
- Monitor therapy with peak and trough levels
- Good gram-negative coverage
- Synergistic with penicillins, cephalosporins
- Tobramycin and amikacin reserved for resistance to gentamicin
- Neomycin used orally for bowel sterilization
- Use
- Intravenously for systemic gram negatives
- Topical
- Ophthalmic and otic
