Which one of the following is true regarding the use of gentamicin?
- It is bacteriostatic
- It has synergistic effects when used along with penicillin
- It is effective against anaerobes
- Nephrotoxicity is dose related
- Ototoxicity is rare
Gentamicin is a bactericidal broad spectrum aminoglycoside antibiotic. It is active against a range of Gram -ve organisms (including E.coli, Pseudomonas, Klebsiella, Proteus and Serratia amongst others) as well as the gram +ve Staphylococcus species (but NOT streptococci) .
Gentamicin enters bacterial cells where it inhibits bacterial protein synthesis by irreversibly binding to the 30s ribosomal subunit. There is a synergism between the beta lactam antibiotics (e.g. penicillins) and gentamicin since beta lactam antibiotics damage bacterial cell wall allowing better intracellular penetration of gentamicin.
Like other aminoglycosides, gentamicin is not active against anaerobes.
The therapeutic range of gentamycin is narrow and adverse effects common. Nephrotoxicity affects 5-25% who receive gentamycin for more than 3 days and ototoxicity similarly 10%. Adverse effects are influenced by dose, frequency and duration of treatment and are minimised by daily monitoring of blood levels followed by dose and frequency adjustment where required.