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Intra Tympanic Medications
Dr. T. Balasubramanian M.S. D.L.O.
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Why ?
• Focused application
• High drug levels where it is needed most
• Use of smaller quantity of the drug
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Round window anatomy
• Round window is about 70 µ thick
• Consists of 3 layers
• Acts as a semi permeable membrane
• Blood labyrinthine barrier
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What drugs can be used ?
• Gentamycin
• Lignocaine
• Steroids
• Inner ear cells could be potential targets for gene therapy
• Calpain inhibitors (leupeptin)
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Lignocaine as I.T. infusion
• Silences the hyper functional neuronal pathways which causes tinnitus
• Causes intense vertigo and nausea
• Effect does not last long hence abandoned
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Indications for intra tympanic steroids
• Idiopathic sudden s/n loss
• Idiopathic rapidly progressive s/n loss
• Otologic manifestations of systemic auto immune disease
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SSNHL
• New onset unilateral hearing loss developing within 72 hours
• Patient feels a sudden pop with development of tinnitus
• Hearing drops precipitously
• Hearing fluctuations are common
• Medical emergency
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Causes of SSNHL
• Traumatic
• Immunologic
• Toxic
• Circulatory
• Neurologic
• Metabolic
• Viral
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Pharmacology of steroids
• Genomic actions
• Non genomic immediate actions
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Action of steroids in the ear
• Anti inflammatory action
• Increases cochlear vascularity
• Reduces degeneration of stria vascularis due to its anti oxidant effects
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What steroid to use ?
• ? Methyl prednisolone
• ? Hydrocortisone
• ? Dexamethosone
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Why Methyl prednisolone ?
• Methyl prednisolone reached high concentration in the inner ear fluids
• This high concentration is retained for a longer period of time.
• The anti inflammatory potential of Methyl prednisolone was the best
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Mode of administration
• Through a middle ear catheter
• Through a grommet
• Continuous infusion pump
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Factors affecting the transfer of drug through round window
• Size of the particle• Charge• Presence of facilitating substances• Thickness of the round window membrane• Presence of inflammation in the round
window membrane
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Facilitators
• Histamine
• Prostaglandins
• Leukotrienes
• E.coli endotoxin
• Staphylococcal exotoxin
• Ethacrinic acid
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Aminoglycosides
• Gets preferentially concentrated in the endolymph
• Damages type I cells preferentially in the ampullar area
• Delivered using Silverstein micro wick technique through a grommet
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Silverstein Micro wick technique
• Made of polyvinyl acetate• Passed through a ventilation tube• The wick is 1mm in diameter and 9 mm long• Drugs can be self administered• Wick must be replaced once a month lest it is
difficult to remove and becomes adherent to round window
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Complications of IT medications
• Persistent perforation
• Mastoiditis
• Deafness
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Role of reactive oxygen species
• Reactive oxygen species causes extensive damage to stria vascularis
• They are extremely toxic to cellular and sub cellular structures
• It is generated by noise trauma and also by aging
• Aminoglycosides cause trauma to cochlea by releasing R.O.S.
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R.O.S. blockers
• Gluthathione
• D. Methionine
• Resveratrol
• Oxygen
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Role of gene therapy
• Improves neuronal survival
• Prevents oxidative stress
• Regenerates auditory and vestibular hair cells
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Gene therapy
• Direct delivery of genes
• Cochlea is suited because it is isolated from the remaining body by the blood labyrinth barrier
• Perilymph permits virus to reach the cochlea hence genes can be transmitted using a virus or non virus vectors
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