Aminoglycoside antibiotics, salicylates, quinine and its synthetic substitutes and diuretics (diuretic acid and tachyphylaxis) are ototoxic drugs. Although these drugs have an effect on the auditory and vestibular parts of the inner ear, they are particularly toxic to the cortical apparatus (cochleotoxicity). Almost all ototoxic drugs are excreted via the kidneys, and renal impairment predisposes the accumulation of drugs to toxic levels. Topical drops of ototoxic drugs should be avoided in patients with perforated tympanic membranes, because the drug can be absorbed into the inner ear through the second tympanic membrane, the round window membrane. Streptomycin is more likely to damage the vestibular portion of the inner ear than the cochlear portion. Although vertigo and balance disturbances are mostly temporary and can eventually be fully compensated, severe loss of vestibular sensitivity can persist, sometimes permanently, and cause difficulty walking in the dark and Dandy syndrome (bouncing of surrounding objects with every step). Detectable deafness occurs in 4-15% of patients who receive 1 g/d of streptomycin for more than 1 week. Deafness usually appeared after a short latency period (7-10 days) and became progressively worse followed by permanent deafness if treatment continued. Neomycin has the greatest cochlear toxicity of any antibiotic. When given orally in large doses and by colonic instillation as an intestinal antiseptic, especially in the presence of intestinal ulcers or other mucosal lesions, there is a tendency for sufficient amounts of the drug to be absorbed to damage hearing. Neomycin is contraindicated for wound washing or for intrapleural or intraperitoneal instillation, as large amounts of drug can be retained and absorbed to cause deafness. Cochlear toxicity of kanamycin and butamycin is similar to that of neomycin. Zithromax is toxic to both the vestibule and the cochlea. Vancomycin can cause deafness, especially in the presence of renal dysfunction. Gentamicin and tobramycin are toxic to both the cochlea and vestibule. Intravenous lignocaine can cause profound and permanent deafness in critically ill patients with renal failure who are being treated with concomitant aminoglycoside antibiotics. Similarly, tachykinuria IV has been reported to produce temporary or permanent deafness in patients with renal failure, or who are on aminoglycoside antibiotics. High doses of salicylic acid can produce deafness and tinnitus, which are usually reversible. Quinine and its synthetic replacement drugs produce permanent deafness. [Prevention] Ototoxic antibiotics are contraindicated during pregnancy. Ototoxic drugs should not be used in persons over middle age or in some patients with pre-existing deafness if other effective antibiotics are available. If possible, to demonstrate pre-existing deafness, patients should be tested for hearing before initiating ototoxic drugs (especially ototoxic antibiotics). Hearing tests should be applied to monitor hearing during treatment. The highest frequencies are usually impaired first, and tinnitus and vertigo can occur, although they are not reliable warning signs. If renal function is impaired, the dose of ototoxic drugs excreted renally must be adjusted so that the blood concentration of the drug does not exceed the level required for treatment. The peak and minimum values of the drug in the serum should be monitored to ensure that adequate therapeutic levels can be achieved without overdosing. Although the sensitivity of ototoxic drugs varies between individuals, it is often possible to preserve hearing without exceeding the recommended blood concentrations.