Detail description of the ototoxicity

1. OTOTOXICITY
Ms. Saheli Ch
LECTURER
IACN

2. INTRODUCTION
• Ototoxicity is quite simply, ear poisoning.
• (Oto= ear, toxicity= poisoning), which results from
exposure to drugs or chemicals that damage the inner
ear or the vestibulo-cochlear nerve (the nerve sending
balance and hearing information from the inner ear to
the brain).

3. DEFINITION

4. CAUSES
# Ototoxic drugs :
• Quinine and salicylates: Tinnitus and hearing loss may occur
due to effect of this drugs.
• Aminoglycosides: destroy the hair cells in the organ of corti.
• Loop diuretics: Permanent sensori neural hearing loss.
• Antiepileptics: Vestibular disorder.
• Betablockers: Deafness.
• Antimalarial.
• Anticancer drugs.
• Analgesics.
• Topical drugs.

5. Aminoglycosides
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Streptomycin, Gentamicin, Tobramycin, Neomyc
in and Kanamycin.
Cochlear toxicity:
Neomycin, Kanamycin, Amikacin.
Vestibular toxicity: Gentamicin, Streptomycin
Pathogenesis: Selectively destroy outer hair
cells, they even destroy inner hair cells.
Symptoms: hearing loss, tinnitus, vertigo

6. Normal inner ear hair cells Damaged inner ear hair cells

7. +
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Diuretics
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Furosemide and Ethacrynic acid (loop diuretics)
Known to cause edema and cystic changes in
stria vascularis of cochlear duct.
The edema is caused due to blockage of Na &
Cl ions transport.
Effect: mostly reversible but permanent damage
may occur.

8. Antimalarials
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Quinine & Chloroquine
Ototoxic effect is due to vasoconstriction in the
small vessels of the cochlea and stria vascularis.
The effect is reversible which generally appears
on prolonged medication, but deafness is
permanent with chloroquine.
Congenital deafness and hypoplasia of cochlea
have been reported in children whose mothers
received these drugs during pregnancy(1
trimester).
st

9. Anticancer drugs
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Nitrogen
mustards(Cyclophosphamide, Ifosfamide), Cispla
tin, Carboplatin can cause cochlear damage.
Ototoxic effect is due to outer hair cell
degeneration leading to high frequency sensory
neural hearing loss.

10. Analgesics
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NSAIDS like Salicylates, Indomethacin, Phenyl
butazone, Ibuprofen.
Ototoxic effect is reversible and is due to
interference at enzymatic level.
No structural damage hence normal
histology(no hair cell loss)
Site of lesion testing indicates cochlear
involvement.
Symptoms: tinnitus and b/l hearing loss
particularly affecting higher frequencies.

11. Topical drugs
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Topical ear drops used in the treatment of otitis
externa may be absorbed from the round and
oval windows into the fluids of inner ear leading
to ototoxicity.
Chlorhexidine which was used in the
preparartion of ear canal before surgery has also
been blamed for such deafness.

12. High risk groups
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Patients having impaired renal function.
Elderly patients(age above 65 yrs).
Patients simultaneously receiving other ototoxic
drugs [aminoglycosides when concomitantly
used with diuretics have synergistic ototoxicity].
Patients who have genetic susceptibility to these
group of drugs.
Patients under prolonged treatment.

13. CLINICAL MANIFESTATION
• The signs and symptoms range from mild tinnitus to
total hearing loss, depending upon each person, and the
form and level of exposure to the ototoxin.
• They can include one sided or two sided hearing loss
and constant or fluctuating tinnitus.
• High pitched tinnitus is often the earliest symptoms.
• Sensorineural deafness.
• Vertigo

14. DIAGNOSTIC EVALUATION
• The diagnosis is based upon the patients history, symptoms and
test results.
• There is no specific test for ototoxicity; this makes a positive
history for ototoxin exposure crucial to the diagnosis.
• Electrocochleography (abbreviated ECochG or ECOG) is a
technique of recording electrical potentials generated in
the inner ear and auditory nerve in response to sound
stimulation, using an electrode placed in the ear canal or
tympanic membrane.

15. • Electronystagmography (ENG) is a diagnostic test to
record involuntary movements of the eye caused by a
condition known as nystagmus. It can also be used to
diagnose the cause of vertigo, dizziness or balance
dysfunction by testing the vestibular system.
• Monitoring drug concentrations in the body.
• BERA ( Brain stem evoked response audiometry): is an
non-invasive method of hearing assessment which
detects electrical activity from the inner ear to the
inferior colliculus.

16. Management
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Early recognition and discontinuation of drugs.
Hearing aid in cases of severe hearing loss.
Tinnitus treated by mild hypnotics.
Disequilibrium should be treated with
reassurance and regular physiotherapy including
vestibular exercises, wearing of soft thick padded
shoes, avoidance of walking in darkness and
unnecessary head movement.

17. • Limit use of ototoxic drugs.
• Periodic ophthalmic/ audiometric
examination
• Treat the underlying causes