Gentamicin Peak, Serum

Laboratory assay overview

Gentamicin is an aminoglycoside antibiotic used in the treatment of gram-positive and gram-negative bacterial infections, especially Pseudomonas, Proteus, Klebsiella and Staphylococcus. Gentamicin is potentially nephrotoxic and ototoxic. Serial monitoring of peak and trough serum levels may provide the clinician with information to maintain safe and therapeutic levels.

Laboratory assay overview

This aminoglycoside is used to treat serious infections caused by aerobic gram-negative bacilli (eg, a number of the Enterobacteriaceae, P aeruginosa ). These include lower respiratory tract, intra-abdominal, soft tissue, bone or joint, wound, and complicated urinary tract infections; bacteremias; and meningitis (by intrathecal administration). Gentamicin often is the preferred aminoglycoside for general use in hospitals where the prevalence of bacterial resistance to this agent is low (based on locally generated antimicrobial susceptibility profiles). Its major advantage over tobramycin, amikacin, and netilmicin is lower cost. The empiric use of gentamicin or tobramycin is not justified in hospitals where gentamicin resistance is common; amikacin is the aminoglycoside of choice in these locales. The combination of gentamicin plus penicillin G (or ampicillin) exhibits synergistic activity against enterococci (eg, Enterococcus faecalis ) and viridans streptococci and frequently is the regimen of choice for the treatment of endocarditis caused by these organisms. Streptomycin is an alternative to gentamicin for streptomycin-susceptible strains of enterococci. Enterococcal clinical isolates with high-level resistance to gentamicin and other aminoglycosides (minimum inhibitory concentrations, >2000 μg/mL) have been reported. Therapy for endocarditis caused by these gentamicin-resistant enterococci is not established, but some isolates do remain susceptible to streptomycin, which may be given with penicillin to treat this infection. Gentamicin is recommended by the American Heart Association for parenteral prophylactic use with ampicillin or vancomycin in patients who are at high risk of developing bacterial endocarditis but are unable to take the standard oral regimen prior to undergoing invasive procedures involving the oral cavity and upper respiratory, gastrointestinal, or genitourinary tract.