Local drug application to the inner ear offers a number of advantages over systemic delivery. Local drug therapy currently encompasses extracochlear administration (intratympanic injection); intracochlear administration, particularly for gene and stem cell therapy; as well as various combinations with auditory neurosensory prostheses, either evaluated in preclinical or clinical studies, or off-label. To improve rehabilitation with cochlear implants (CI), one focus is the development of drug-releasing electrode carriers, e. g., to deliver glucocorticosteroids, antiapoptotic substances, or neurotrophines to the inner ear. By protecting neuronal structures from insertion trauma, reducing fibrosis in the inner ear, and by stimulating growth of neuronal structures in the direction of the electrodes, the performance of CIs should be improved. Controlled drug release after extracochlear or intracochlear application in conjunction with a CI can be achieved by, e.g., use of a biocompatible, resorbable controlled-release drug delivery systems. Two case reports are presented. In order to treat worsened speech discrimination and increased impedance, these CI-wearing patients successfully underwent intracochlear placement of a biocompatible, resorbable drug delivery system for controlled release of dexamethasone. The drug levels reached in inner ear fluids after different types of local drug application strategies can be calculated using computer models. The intracochlear drug concentrations calculated in this way were compared for different dexamethasone application strategies.
Keywords: Cochlea; Cochlear implant; Drug therapy; Impedance; Inner ear.