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Ototoxicity

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Ototoxicity

Ototoxicity

Published in: Health & Medicine, Technology
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  • 1.  Definition  Damage to the cochlea or vestibular apparatus from exposure to a chemical source  Many sources  Mercury  Herbs  Streptomycin  Dihydrostreptomycin  Gentamicin  Others
  • 2.  Streptomycin, kanamycin, neomycin, amikacin, gentamicin, tobramycin, sisomycin, netilmicin  Enter into inner ear by unknown mechanism  Secreted into the perilymph by spiral ligament or endolymph by stria vascularis  Diffuse through round window membrane
  • 3.  Cochlear toxicity  Amikacin, kanamycin, neomycin, netilmicin  Vestibular toxicity  Streptomycin, gentamicin, sisomycin
  • 4.  Cochlear toxicity  Increase of 10-20 dB in thresholds of one or more frequencies  Incidence (6-13%), netilmicin lowest  Risk factors  Diuretics, renal failure, prolonged treatment, old age, preexisting SNHL  Infants less affected, once daily dosing
  • 5.  Cochlear toxicity presentation  High frequency SNHL first, then lower frequencies to profound loss  Not reversible  Damage usually heralded by tinnitus
  • 6.  Vestibular toxicity  Dynamic posturography can detect  Clinically  Ataxic gait, lose balance when turning  Bobbing oscillopsia
  • 7.  Prevention  Consider less ototoxic drugs (netilmicin)  Identify “high-risk” patients  Audiogram before and weekly after starting  ENG prior if possible  History and physical exam daily (Romberg, VA)  Adjust doses or switch drugs if toxic
  • 8.  Erythromycin  Clinically  Hearing loss with/without tinnitus– 2 days  All frequencies, recovery after stopping  Rarely permanent (hepatic)
  • 9.  Vancomycin  Believed to be ototoxic (no data)  Penicillin, sulfonamides, cephalosporins  May have topical toxicity in middle ear
  • 10.  Ethacrinic acid, furosemide, bumetaside  Clinically (6-7%)  Usually tinnitus, temporary and reversible SNHL, rare vertigo within minutes  High doses can cause permanent SNHL  Highest risk– coadministration of aminoglycosides
  • 11.  Most common OTC drugs in US  Mechanism  Normal histology (no hair cell loss)  Decreased blood flow, decreased enzymes  Clinically  Tonal, high frequency tinnitus (7-9 kHz)  Reversible mild to moderate SNHL (usually high frequency)– rarely permanent
  • 12.  Similar clinical findings with aspirin  Clinically  High-pitched tinnitus  Reversible, symmetric SNHL  Occasional vertigo  Mechanism  Decreased perfusion, direct damage to outer hair cells, biochemical alterations
  • 13.  Cisplatin  Incidence is high (62%-81%)  Pathologically  Outer hair cell degeneration  Clinically  Bilateral symmetric SNHL, usually high frequency– not reversible, cumulative  Risks factors– age extremes, cranial irradiation, high dose therapy, high cumulative dose
  • 14.  Polymixin B (Brummett)  Chloramphenicol (Patterson)  Neomycin (Brummett)  Gentamicin (Webster)  Ticarcillin (Jakob)  Vasocidin (Brown)  Ciprofloxacin (Lenarz)

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