The progress of topical drug delivery to the inner ear for the inhibition of inflammation and fibrosis following cochlear implantation

Abstract

Nowadays, more than 300 000 deaf people around the world benefit from cochlea implantation. With the extension of cochlear implantation indications, it has become a research focus for how to apply the anti-inflammatory and anti-fibrotic drugs safely and effectively to better retain residual hearing, as well as to protect hair cells and the spiral ganglion cells from apoptosis. Due to the blood-labyrinth barrier, perioperative systemic steroids are often unable to achieve satisfactory drug concentration in the inner ear. Also, given that higher doses of steroids will cause more serious side effects and sometimes steroids are strictly limited to apply on some patients with certain diseases, the attention has been attracted on topical drug delivery to the inner ear. In this review, the methods of topical drug delivery to the inner ear are divided into four categories: transtympanic injection of liquid solutions, tympanic implantation of drug delivery systems, intracochlear injection and modified implant electrode. The results in each category and up to date progress are reviewed.