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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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