The medical issues surrounding gentamicin administration and resulting ototoxicity and nephrotoxicity can be divided into 6 broad categories as set forth below. Links are provided to pages with a more in-depth analysis of each of these categories.
Physiologic Basis of Gentamicin Poisoning. Gentamicin is toxic to the hair cells of the inner ear, and to certain cells in the kidney. As a result, a person on gentamicin can suffer ototoxicity (damage to the inner ear) which is more precisely referred to as bilateral vestibulopathy, and acute renal failure (kidney damage). The bilateral vestibulopathy is usually permanent, and acute renal failure, or nephrotoxicity, is usually transient. Occasionally, gentamicin causes more damage to one ear than the other, leaving a person with a unilateral rather than bilateral total loss.
Appropriate Choice of Antibiotic. Although considered for decades to be a "big gun" in antibiotic therapy, newer anti-pseudomonal beta-lactame antibiotics have provided safer alternatives to gentamicin in most pseudomonal infections. Other superior alternative antibiotics exist for Staphylococcus aureus infections. Certain highly resistant infections might justify the judicious use of gentamicin as a primary antibiotic, at least for a short period of time. Emperic, short term use prior to obtaining definitive culture and sensitivity reports might also be justified.
Enterococcal Endocarditis.Infective endocarditis is defined as an infection of the endocardial surface of the heart, which may include one or more heart valves, the mural endocardium, or a septal defect. Infective endocarditis is caused by a variety of pathogens. Of particular interest here is endocarditis caused by the organisms Enterococcus faecalis and Enterococcus faecium, because it represents one of the few instances where the use of gentamicin is currently justified.
Appropriate Dosing of Gentamicin Appropriate dosing requires adjusting the actual amount of gentamicin given per day to the patient's particular infectious process and to the patient's physiologic parameters. Dosing considerations in monotherapy or true combination therapy are different than when using gentamicin for synergistic effect.
Appropriate Monitoring of Gentamicin. Monitoring is an ongoing process of obtaining serum gentamicin levels, obtaining serum creatinine and Blood Urea Nitrogen (BUN) levels, and carefully observing the patient for physical symptoms of ototoxicity. The requirements for appropriate monitoring are dependent on the dose of gentamicin given per day, the duration of expected treatment, the patient's age, and the patient's pre-treatment and ongoing renal function.
Length of Treatment Issues. The length of time that a patient is exposed to gentamicin is a significant factor in developing nephrotoxicity and ototoxicity. While the traditional notion of antibiotic therapy ensuring complete eradication of the target organism is important, the toxic nature of gentamicin dictates that its course be kept to an absolute minimum