Drugs particularly notorious for ototoxicity include the aminoglycoside antibiotics (streptomycin, kanamycin, neomycin, gentamicin, and viomycin), salicylates, the diuretics ethacrynic acid and furosemide, and quinine or chloroquine. Although both the vestibular and auditory portions of the inner ear can be affected, streptomycin, gentamicin, and viomycin are especially toxic to the vestibular system, while neomycin, kanamycin, and amikacin are more toxic to the auditory system.
Salicylates in large doses can cause a reversible hearing loss, tinnitus, and vertigo. The symptoms generally appear with plasma concentrations of about 35 mg/dL. Ethacrynic acid, when administered IV, is associated with permanent hearing loss; coadministered aminoglycoside appears to be an aggravating factor. Furosemide may cause temporary hearing loss. Quinine and chloroquine are associated with both permanent and temporary hearing losses, the former occurring with large doses. Chemotherapeutic agents, particularly nitrogen mustard and cisplatin, are implicated in sensorineural hearing loss.
The elderly, especially those with hearing loss or renal dysfunction, should not be treated with ototoxic drugs unless no suitable alternative exists. In such a case, a baseline and follow-up audiogram should be obtained to document any drug-related changes. Vestibular effects may be insidious, particularly when patients are bedridden. A bedside test of the vestibulo-ocular reflex may help in early detection of vestibular dysfunction.
Although the perilymph of the inner ear tends to concentrate and retain certain ototoxic drugs, regular serum monitoring for therapeutic blood levels helps avoid ototoxicity.