Academic journal article The Volta Review

Audiological Management of Patients Receiving Aminoglycoside Antibiotics

Academic journal article The Volta Review

Audiological Management of Patients Receiving Aminoglycoside Antibiotics

Article excerpt

Aminoglycoside antibiotics, commonly prescribed for adults and children to treat a wide range of bacterial infections, are potentially ototoxic, often causing irreversible damage to the auditory and vestibular systems. Ototoxic hearing loss usually begins at the higher frequencies and can progress to lower frequencies necessary for understanding speech. Individual susceptibility to aminoglycoside ototoxicity is determined by multiple physiologic and genetic factors. Children are especially vulnerable to ototoxic-induced damage, which can affect speech and language development even when limited to the high frequencies. Monitoring hearing loss during and after treatment by conventional and ultra-high frequency audiometry allows early detection of ototoxic hearing loss. Objective measures such as auditory brainstem responses (ABRs) and otoacoustic emissions (OAEs) can provide information about auditory function for individuals unable to provide reliable behavioral data, including young children. Early detection and subsequent alteration of treatment, as well as the potential future use of otoprotectants, may minimize or prevent ototoxic hearing loss.

Aminoglycoside antibiotics were developed in the 1940s as a first-line therapy for aerobic gram-negative bacterial infections. Streptomycin was widely used for the effective treatment of tuberculosis. Antibiotics developed subsequently, such as neomycin, gentamicin, tobramicin, amikacin, kanamycin and netilmicin, successfully treat many bacterial infections including those associated with meningitis, wounds, osteomyelitis and cystic fibrosis. In pédiatrie populations, gentamicin is commonly prescribed for the medical management of neonates in the neonatal intensive care unit, and tobramycin is used for children with cystic fibrosis. In addition to their effectiveness, aminoglycoside antibiotics demonstrate a low incidence of Clostridium difficile diarrhea compared to other antibiotics, are relatively inexpensive and present a low risk of allergic reactions (Edson & Terrell, 1999). Despite the advantages of these medications, many are highly ototoxic, causing damage to the auditory and/or vestibular systems. For this reason, the use of some aminoglycoside antibiotics have been limited or replaced by alternative, less ototoxic antibiotics, such as third generation cephalosporins. However, the re-emergence of tuberculosis and the rise in resistant organisms has recently increased the use of aminoglycoside antibiotics having ototoxic potential.

Ototoxicity is most often associated with antibiotics administered intravenously in adults, but these drugs can also be administered in aerosolized solutions or as topical preparations. Examples of drug administration in children include intravenous administration of gentamicin for sepsis in neonates (see Pillers & Schleiss, 2005, this issue) and aerosolized nebulizer treatments of tobramycin for cystic fibrosis, nosocomial pnemonia and sometimes bronchiectasis. Aerosolized solutions appear to be less ototoxic than injected preparations, and topical skin applications are rarely ototoxic unless they involve large, compromised areas such as in burn victims. However, the ototoxic potential of aminoglycoside ear drop formulations is a current area of debate.

Topical ear drops containing tobramicin or corticosporin with neomycin are standard treatment for otitis externa or otitis media with perforation. Antibiotics can enter the inner ear by diffusion across the round window membrane. Many animal studies have documented ototoxicity even from a single dose of corticosporin drops (Roland, 2004), however, the human ear appears to be less susceptible to topical preparations of aminoglycosides possibly due to a thicker and less accessible round window membrane. A perforation of the tympanic membrane, or surgical placement of a ventilation (pressure equalization) tube for the treatment of chronic otitis media, potentially allows the antibiotic to be delivered directly into the middle ear space, increasing the likelihood of transmission across the round window membrane (Bath, Walsh, Bance, & Rutka, 1999). …

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