Steroid intracochlear distribution differs by administration method: Systemic versus intratympanic injection

Abstract

OBJECTIVE: Steroids have been widely used to treat inner-ear diseases such as sudden sensorineural hearing loss, tinnitus, and Meniere's disease. They can be given via either systemic or intratympanic (IT) injection. The purpose of the present study was to explore differences in intracochlear steroid distribution by the administration method employed (systemic vs. IT injection). STUDY DESIGN: Animal study. METHODS: Twenty-three Sprague-Dawley rats were given fluorescein isothiocyanate-labeled dexamethasone (FITC-DEX) three times (on successive days) via intraperitoneal (IP) or IT injection. Cochlear uptake of FITC-DEX was evaluated via immunohistochemistry and flow cytometry at 6 hours, and 3 and 7 days after the final injection. RESULTS: FITC-DEX uptake was evident in spiral ganglion cells (SGs), the organ of Corti (OC), and the lateral walls (LWs), the basal turns of which were stained relatively prominently in both groups. Animals receiving IP injections exhibited higher FITC-DEX uptakes by the SGs and OC, whereas IT injection triggered higher-level FITC-DEX accumulation by the OC and LWs. Flow cytometry revealed that intracochlear FITC-DEX uptake by IT-injected animals was higher and more prolonged than in animals subjected to IP injections. CONCLUSION: We thus describe differences in cochlear steroid distributions after systemic and IT injections. This finding could help our understanding of the pharmacokinetics of steroids in the cochlea. LEVEL OF EVIDENCE: NA.