In the clinic, there are many conditions affecting the ear that can benefit from treatment with locally-applied drugs. They include:-
1) Meniere's disease - which has symptoms of rotatory vertigo (the sensation of spinning), hearing loss to sounds of low pitch, tinnitus (hearing roaring or whistling sounds when in a quiet room) and a feeling of "fullness" or pressure in the ear.
2) Sudden hearing loss - If you wake up one morning and the sensitivity of hearing in one or both ears has declined. You feel deaf and cannot hear quiet sounds (such as the ticking of a clock). Typically you need to urgently contact your ENT (ear nose & throat) doctor or otologist.
In either of these cases, doctors are now commonly using intratympanic therapy, which is a procedure where drug solution is injected through the eardrum (tympanic membrane) into the middle ear space. From the middle ear the drug (shown green below) can spread into the inner ear. This allows drug to reach the inner ear at much higher concentrations than they would if given systemically (such as by intravenous injection or orally).
The drugs commonly used are steroids (dexamethasone-phosphate or methylprednisolone-hemisuccinate) or gentamicin, which is used to suppress dizziness caused by a hyperactive or unstable balance system.
In our research, we are interested in how much of the applied drug gets into the inner ear, whereabouts in the ear the drug distributes to, and how long the drug remains in the ear. Others have numerous new therapies "in-the-pipeline" which may treat a wider range of inner ear disorders.
In general, we have found that applied drugs are lost very rapidly from the middle ear so that entry into the inner ear occurs only briefly. Many drugs are lost quickly from perilymph so they do not get chance to distribute to apical regions and only briefly treat basal regions of the ear. However, new delivery methods are becoming available that now allow drugs to be distributed throughout the human cochlea, albeit using more invasive surgical techniques. Improving the quantitaive reliability of drug applications to the ear will undoubtedly improve their effectiveness.