A simple and Cost-effective Method to Determine Dexamethasone in Murine Cochlea Using Solvent Extraction and Multiple Reaction Monitoring

Dexamethasone (DEX) is a glucocorticoid commonly used to treat idiopathic sudden sensorineural hearing loss (ISSNHL) and inner ear disorders like Meniere's disease. However, systemic administration of DEX is associated with significant side effects, such as hypertension and peptic ulcer, highlighting the need for safer and more effective intratympanic (IT) formulations and reliable methods for their in vivo evaluation. However, methods to determine DEX in the cochlea require a tissue lyser, uncommon in laboratories for instrumental analyses, and their analytical performances have not been validated. To address these issues, a simple and cost-effective method to determine DEX in murine cochlear tissue was developed using triamcinolone acetonide as the internal standard (IS), acetonitrile as a single extraction solvent, and LC-MS/MS as an instrumental method. The developed method was successfully validated through selectivity, linearity (r² ≥ 0.999 within 1–500 ng/mL), accuracy (ranging from 86.8% to 100.2%), precision (≤ 5.8%), matrix effect (91.56% to 104.46%), recovery (93.1% to 104.5%) and the lower limit of quantitation (1.0 ng/mL) following FDA guidelines. This method is expected to contribute to the development of novel formulations for IT delivery of DEX for inner ear disorders.