Title:Drug Delivery to the Inner Ear: Strategies and Their Therapeutic Implications for Sensorineural Hearing Loss
Volume: 9
Issue: 3
Author(s): Teresa Rivera, Lorena Sanz, Guadalupe Camarero and Isabel Varela-Nieto
Affiliation:
Keywords:
Sensorineural deafness, intratympanic, intracochlear, local therapy, mutant mice, microcathether, round window,
osmotic pump, cochleostomy.
Abstract: Hearing aids or cochlear implants constitute almost exclusively the treatment options currently available to
patients suffering from sensorineural hearing loss and related conditions, such as noise-induced hearing loss, ototoxicity
or autoimmune inner ear disease. While some systemic treatments exist, they generally exert adverse secondary effects
and their efficacy is hampered by the blood-cochlear barrier that limits drug access to the inner ear. Hence, the new therapies
that are being developed for hearing loss focus on strategies for direct drug delivery to the inner ear. The passive and
active methods for local delivery can be categorized into two general groups: intratympanic or intracochlear. The intratympanic
approach is a non-invasive method that preserves hearing and takes advantage of the permeability of the round
window to gain access to the cochlea. However, this technique is limited by not knowing the dose of the drug that reaches
the cochlea, (a handicap whichmight be overcome by the use of tagged drugs). While direct access to the inner ear by
intracochlear administration avoids this problem, this method requires surgery. Currently, laboratory animals are being
used to explore which therapeutic approaches are best suited to address this problem. These include cochleostomy and the
insertion of devices that pump drugs into the inner ear without inducing cochlear damage. In this article, we review the
different techniques under evaluation in animal models of deafness, and their potential use for drug delivery and treatment
of human inner ear diseases.
