Ototoxicity

Detail description of the ototoxicity

1. OTOTOXICITY
Ms. SaheliCh
LECTURER
IACN

2. INTRODUCTION
•Ototoxicityis 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
# Ototoxicdrugs :
•Quinine and salicylates: Tinnitus and hearing loss mayoccur
due to effect of thisdrugs.
•Aminoglycosides: destroy the hair cells in the organ of corti.
•Loop diuretics: Permanent sensori neural hearingloss.
•Antiepileptics: Vestibulardisorder.
•Betablockers:Deafness.
•Antimalarial.
•Anticancer drugs.
•Analgesics.
•Topical drugs.

5. Aminoglycosides
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Streptomycin,Gentamicin,Tobramycin,Neomyc
inandKanamycin.
Cochleartoxicity:
Neomycin,Kanamycin,Amikacin.
Vestibulartoxicity:Gentamicin,Streptomycin
Pathogenesis:Selectivelydestroyouterhair
cells,theyevendestroyinnerhaircells.
Symptoms:hearingloss,tinnitus,vertigo

6. Normalinnerearhaircells Damagedinnerearhaircells

7. +
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Diuretics
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FurosemideandEthacrynicacid(loopdiuretics)
Knowntocauseedemaandcysticchangesin
striavascularisofcochlearduct.
TheedemaiscausedduetoblockageofNa&
Clionstransport.
Effect:mostlyreversiblebutpermanentdamage
mayoccur.

8. Antimalarials
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Quinine&Chloroquine
Ototoxiceffectisduetovasoconstrictioninthe
smallvesselsofthecochleaandstriavascularis.
Theeffectisreversiblewhichgenerallyappears
onprolongedmedication,butdeafnessis
permanentwithchloroquine.
Congenitaldeafnessandhypoplasiaofcochlea
havebeenreportedinchildrenwhosemothers
receivedthesedrugsduringpregnancy(1
trimester).
st

9. Anticancerdrugs
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Nitrogen
mustards(Cyclophosphamide,Ifosfamide),Cispla
tin,Carboplatincancausecochleardamage.
Ototoxiceffectisduetoouterhaircell
degenerationleadingtohighfrequencysensory
neuralhearingloss.

10. Analgesics
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NSAIDSlikeSalicylates,Indomethacin,Phenyl
butazone,Ibuprofen.
Ototoxiceffectisreversibleandisdueto
interferenceatenzymaticlevel.
Nostructuraldamagehencenormal
histology(nohaircellloss)
Siteoflesiontestingindicatescochlear
involvement.
Symptoms:tinnitusandb/lhearingloss
particularlyaffectinghigherfrequencies.

11. Topicaldrugs
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Topicaleardropsusedinthetreatmentofotitis
externamaybeabsorbedfromtheroundand
ovalwindowsintothefluidsofinnerearleading
toototoxicity.
Chlorhexidinewhichwasusedinthe
preparartionofearcanalbeforesurgeryhasalso
beenblamedforsuchdeafness.

12. Highriskgroups
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Patientshavingimpairedrenalfunction.
Elderlypatients(ageabove65yrs).
Patientssimultaneouslyreceivingotherototoxic
drugs[aminoglycosideswhenconcomitantly
usedwithdiureticshavesynergisticototoxicity].
Patientswhohavegeneticsusceptibilitytothese
groupofdrugs.
Patientsunderprolongedtreatment.

13. CLINICAL MANIFESTATION
•Thesignsandsymptomsrangefrommildtinnitusto
totalhearingloss,dependinguponeachperson,andthe
formandlevelofexposuretotheototoxin.
•Theycanincludeonesidedortwosidedhearingloss
andconstantorfluctuatingtinnitus.
•Highpitchedtinnitusisoftentheearliestsymptoms.
•Sensorineuraldeafness.
•Vertigo

14. DIAGNOSTIC EVALUATION
•Thediagnosisisbaseduponthepatientshistory,symptomsand
testresults.
•Thereisnospecifictestforototoxicity;thismakesapositive
historyforototoxinexposurecrucialtothediagnosis.
•Electrocochleography(abbreviatedECochGorECOG)isa
techniqueofrecordingelectricalpotentialsgeneratedin
theinnerearandauditorynerveinresponsetosound
stimulation,usinganelectrodeplacedintheearcanalor
tympanicmembrane.

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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Earlyrecognitionanddiscontinuationofdrugs.
Hearingaidincasesofseverehearingloss.
Tinnitustreatedbymildhypnotics.
Disequilibriumshouldbetreatedwith
reassuranceandregularphysiotherapyincluding
vestibularexercises,wearingofsoftthickpadded
shoes,avoidanceofwalkingindarknessand
unnecessaryheadmovement.

17. •Limit use of ototoxicdrugs.
•Periodic ophthalmic/ audiometric
examination
•Treat the underlyingcauses