ototoxin

An ototoxin is any substance that damages the structures of the inner ear, particularly the cochlea or vestibular apparatus, leading to hearing loss, tinnitus, or balance problems. Ototoxic effects can arise from drugs, environmental chemicals, or occupational exposures, and are often dose-related.

Ototoxins most frequently damage sensory hair cells or their supporting cells. In mammals, outer hair cells are especially vulnerable, and injury may involve oxidative stress, mitochondrial dysfunction, or disruption of ion transport in the endolymphatic system. Damage can be reversible if exposure is halted early, but is often permanent with continued exposure.

Common examples include aminoglycoside antibiotics (such as gentamicin, amikacin), platinum-based chemotherapy (cisplatin, carboplatin), loop diuretics (furosemide), high-dose aspirin or other NSAIDs, and certain solvents or industrial chemicals (for example toluene). Individual risk depends on age, renal function, genetic factors, and prior hearing loss.

Diagnosis is usually by audiometry, with additional tests like otoacoustic emissions or vestibular assessment as needed. Baseline testing before starting known ototoxins and periodic monitoring during treatment help guide dose adjustments and may prompt drug changes. Management emphasizes exposure avoidance, rehabilitation for residual deficits, and use of hearing aids or vestibular therapy.

Prevention focuses on minimizing exposure, monitoring organ function (notably kidneys), and thorough patient education. In humans and animals, limited hair cell regeneration means recovery is often partial. Research continues into protective strategies and the development of less ototoxic therapies.