Ototoxicity

Ototoxicity describes a toxin that affects the ear and its associated structures - the cochlea, the auditory nerve and/or the inner ear. They can affect both hearing and balance. The effect may be temporary and will disappear when the toxin is processed by the body, or can be permanent and last even though no trace of the toxin remains. Ironically, the majority of ototoxic chemicals are pharmaceuticals and this side effect has been known since the 19th century.
Ototoxic drugs are generally only used as drugs of last resort for very serious conditions. However, they can range from antibiotics to diuretics and chemotherapy agents. 
Ototoxicity usually manifests with hearing loss, vertigo and tinnitus. If these symptoms begin during treatment, a physician must balance the serious side effect with the consequences of discontinuing treatment.
Ototoxicity at Wikipedia