Ototoxicity

OTOTOXICITY—DANIEL TODD, MD
A GENERAL TERM TO REFER TO THE COMBINATION OF COCHLEO- AND VESTIBULOTOXICITY
ALWAYS EXACERBATED BY IMPAIRED RENAL FUNCTION (OTO AND NEPHRO TOXICITY OFTEN GO HAND IN HAND)
LOOP DIURETICS—BESIDES BEING COCHLEOTOXIC THEMSELVES ALSO HEIGHTEN THE TOXICITY OF OTHER MEDS
ALWAYS CUMULATIVE—WORSE WITH PRE-EXISTING SNHL
OFTEN IRREVERSIBLE—-IF EFFECTS STILL PRESENT AFTER 2-3 WEEKS THE DAMAGE IS PROBABLY PERMANENT
COCLEOTOXICITY—-THE MOST COMMON!!!!!
MOST COMMON MECHANISM=DAMAGE TO THE TYPE I (>TYPE II) OUTER (>INNER) COCHLEAR HAIR CELLS PRIMARILY IN THE BASAL TURN (>APEX)[HIGHER FREQUENCIES] OF THE COCHLEA (ALSO SOME DAMAGE TO REISSNER’S MEMBRANE AND OTHER SUPPORTING CELLS
AMINOGYLCOSIDES-GENERAL-ABX WITH BACTERIOCIDAL ACTIVITY AGAINST GRAM – ORGANISMS, ESPECIALLY PSEUDOMONAS
-ACT BY BLOCKING RIBOSOMAL PROTEIN SYNTHESIS AND RESULTS IN BUILD-UP OF TOXIC BY- PRODUCTS
-CROSSES PLACENTA BUT NOT BBB
-POOR GI ABSORPTION
-EXCRETED BY KIDNEYS WITH MINIMAL METABOLISM
-HAS SYNERGISTIC EFFECT WITH B-LACTAMASE RESISTANT ABX
DIHYDROSTREPTOMYCIN —GIVEN ONLY IN THE LATE 40’S, EARLY 50’S FOR TB!
NEOMYCIN – COCHLEA/VEST.  AND NEPHROTOXIC
KANAMYCIN
AMIKAMYCIN
TOBRAMYCIN, NETILMYCIN
QUININE, QUINIDINE, CHLOROQUIN –CINCHONISM (FROM THE CINCHONA TREE)—HA, BLURRED VISION, VERTIGO, N/V, SNHL, TINNITUS
VANCOMYCIN    -EFFECTS ARE POTENTIATED BY GENTAMICIN AND ERYTHROMYCIN
ERYTHROMYCIN    -MOSTLY GIVES REVERSIBLE DOSE DEP SNHL LIKE ASA
CISPLATIN, BLEOMYCIN
-MAY GIVE EITHER A HIGH FREQUENCY SNHL OR VESTIBULAR SYMPTOMS; ALSO NEPHROTOXIC
-DOSE DEPENDENT TOXICITY THAT AFFECTS MAINLY THE OUTER HAIR CELLS—?HYDRATION RELATED
-EFFECT POTENTIATED BY LOOP DIURETICS
NITROGEN MUSTARDS, CHLORAMPHENICOL, MINOCYCLINE, LEAD, BENZENE, CO, DISULFIDE, POVIDONE, IODINE
OTHER MECHANISMS:
STRIAL DEGENERATION—AN IONIC GRADIENT CANNOT BE MAINTAINED
DIURETICS    -LASIX AND ETHACRYNIC ACID—–
-OCCUR WITH RAPID, LARGE, IV BOLUS ADMINISTRATIONS
-REVERSIBLE IF DOSE LOWERED
DOSE DEPENDENT REVERSIBLE TOXICITY WITH VASCULAR INVOLVEMENT (STRIA VASCULARIS)
ASA/SALICYLATES
-REVERSIBLE SNHL AND TINNITUS(SALICYSM)
-NOISE EXPOSURE MAY ACT AS A POTENTIATING FACTOR
VESTIBULOTOXICITY—PRIMARILY THE TYPE I (>TYPE II) HAIR CELLS OF THE CRISTAE AMPULLARIS OF THE UTRICLE (>SACCULE)
SYMPTOMS=DYSEQUILIBRIUM LEADING TO OSCILLOPSIA
UNCOMFORTABLE IN THE DARK (RELY VERY MUCH ON THEIR EYES)
+ RHOMBERG
– VOR
INABILITY TO FIXATE ON IMAGE!
DANDY’S SYNDROME OF JUMBLING PANORAMA AND BOBBING OSCILLOPSIA
ILLEGIBLE “E” TEST= ABNL VOR—-DO A HEAD SHAKE AND THE PATEINT WILL DROP MORE THAN 2 LINES ON A SNELLEN CHART—PT READING CHART WHILE SHAKING HEAD!
ABNL REFIXATION SACCADES=ABNL VOR
ABNL ROTORY CHAIR TESTING=THE MOST SENSITIVE INDICATOR OF VESTIBULOPATHOLOGY—-VOR GAIN IS DECREASED AT LOW FREQUENCIES
STREPTOMYCIN – VEST. > COCHLEA
GENTAMICIN – MOST OTOTOXIC WITH VEST. > COCHLEA
TOBRAMYCIN – INTERMEDIATE TOXICITY TO BOTH
-RISK FACTORS    -OLD AGE
-POOR RENAL FXN
-HIGH PEAK AND TROUGH LEVELS
-PREVIOUSLY GIVEN AMINOGLYCOSIDES
-PRE-EXISTING OTOLOGICAL DZ
-EFFECTS COMPOUNDED IF GIVEN SIMULTANEOUSLY WITH LOOP DIURETICS, INDOCIN, OR
VANCOMYCIN
-OTHER TOXICITY    -NEPHROTOXIC- MAY LEAD TO PROTEINURIA OR AZOTEMIA
-CAN ACT AS A NEUROMUSCULAR BLOCKADE
-ALLERGIC RXN
TESTING -SOME ADVOCATE AT LEAST WEEKLY IF NOT BIWEEKLY AUDITORY TESTING WITH DRUG BEING USED—-CONCENTRATE ON THE HIGHER FREQUENCIES
-CONSIDER ROTARY CHAIR TESTING
Rx: PT EDUCATION—-AVOID FURTHER INSULT
AVOID VESTIBULAR SUPPRESSANTS
VESTIBULAR REHAB

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