A wide variety of drugs can be ototoxic.
Factors affecting ototoxicity:
Ototoxic drugs should not be used for otic topical application when the tympanic membrane is perforated because the drugs might diffuse into the inner ear.
Can be used 7-10 days without being ototoxic, even if the patient has a perforated TM.
Some mitochondrial DNA mutations predispose to aminoglycoside ototoxicity.
due to interference with K ions in endolymph
Streptomycin:
Vertigo tends to be temporary
Severe loss of vestibular sensitivity may persist, sometimes permanantly. Loss of vestibular sensitivity causes difficulty walking, especially in the dark, and oscillopsia (a sensation of bouncing of the environment with each step).
About 4 to 15% of patients who receive 1 g/day for > 1 week develop measurable hearing loss, which usually occurs after a short latent period (7 to 10 days) and slowly worsens if treatment is continued. Complete, permanent deafness may follow.