Abstract
Dexamethasone is widely used in preclinical studies and clinical trials to treat inner ear disorders. The results of those studies vary widely, maybe due to the different dexamethasone formulations used. Laboratory (lab) and medical grade (med) dexamethasone (DEX, C22H29FO5) and dexamethasone dihydrogen phosphate-disodium (DPS, C22H28FNa2O8P) were investigated for biocompatibility and bio-efficacy in vitro. The biocompatibility of each dexamethasone formulation in concentrations from 0.03 to 10,000 µM was evaluated using an MTT assay. The concentrations resulting in the highest cell viability were selected to perform a bio-efficiency test using a TNFα-reduction assay. All dexamethasone formulations up to 900 µM are biocompatible in vitro. DPS-lab becomes toxic at 1000 µM and DPS-med at 2000 µM, while DEX-lab and DEX-med become toxic at 4000 µM. Bio-efficacy was evaluated for DEX-lab and DPS-med at 300 µM, for DEX-med at 60 µM, and DPS-lab at 150 µM, resulting in significantly reduced expression of TNFα, with DPS-lab having the highest effect. Different dexamethasone formulations need to be applied in different concentration ranges to be biocompatible. The concentration to be applied in future studies should carefully be chosen based on the respective dexamethasone form, application route and duration to ensure biocompatibility and bio-efficacy.
Highlights
More than 5% of the world’s population is living with a hearing disability [1,2]
The aim of the current study is to examine whether different formulations of dexamethasone show different levels of in vitro cytotoxicity and differences in bio-efficacy
600 μM, the tested dexamethasone concentrations were increased to 10,000 μM to detect a toxicity limit
Summary
Inflammation-suppressing substances, such as glucocorticoids, and especially dexamethasone, have been widely tested as a potential therapy to treat inner ear pathologies including sudden sensorineural hearing loss (SSNHL) [7–10], Menière’s disease [11–14], and acute tinnitus [15]. The CI electrode array is implanted into the cochlea of the inner ear, stimulating the primary auditory neurons and eliciting a hearing sensation. The benefit in speech perception and hearing of noises that patients have with a CI is tremendous, but in some cases, insertion trauma and foreign body reaction lead to an inflammation.
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