Studies On Dexamethasone-loaded Tympanic Delivery Systems For Treating Inner Ear Diseases Via The Round Window

Treatment of inner ear diseases is an expanding scientific field and remains a serious challenge for inner ear researchers. The keys to successful pharmacological treatment are knowledge of the pathophysiology of the diseases, well-defined therapeutic drugs, and reasonable administration of drugs applied to the pathological site. The barrier system in the inner ear (blood-inner ear barrier, BIB) is functionally similar to the BBB (blood-brain barrier) in regulating the transport of various substances from blood to inner ear tissue and maintaining the microhomeostasis and functional integrity of the inner ear. Tight junctions serve as the structural basis of BIB and extend the normal function that limits the passage of certain drugs into the inner ear. There is an increasing interest in the r.w. administration to the inner ear. The Round window (r.w.) is probably the most important interface between the middle ear and inner ear that can be used for local pharmacological therapy of inner ear diseases. The r.w. administration of drugs involves the delivery of medication directly into the inner ear via the r.w. membrane. Among several means of r.w. administration, the intratympanic administration is more convenient, and applied in clinical trials. However, the common problems existing in the intratympanic administration include the short retention time of ordinary drops in tympanum due to be quickly removed through Eustachian tube, resulting in frequent administration. Another is the probability of producing adverse effect when the drugs get into gastrointestinal tract after expelling through Eustachian tube. These promote more effective tympanic drug delivery systems with better compliancy to be developed.Thermosensitive in situ gels refer to the polymer solutions can be administrated as liquid, which undergo a phase transition to a non-crosslinked semisolid gel upon exposure to physiological temperature and release the drug.