OTOTOXICITY or Ototoxic drugs

Definition: Damage to the inner ear caused by drugs/chemicals leading to sensorineural hearing loss (SNHL), tinnitus, and sometimes vertigo.

1. Aminoglycoside Antibiotics

Mechanism: Binds to ribosome → interferes with protein synthesis → death of cochlear cells.

Type	Drugs	Target Site
Vestibulotoxic	Streptomycin, Gentamicin, Tobramycin.	Type I Hair Cells (Crista Ampullaris).
Cochleotoxic	Neomycin, Kanamycin, Amikacin, Sisomycin, Dihydrostreptomycin.	Outer Hair Cells (Basal coil → Apex).

2. Diuretics (Loop Diuretics)

• Drugs: Furosemide, Bumetanide, Ethacrynic acid.
• Mechanism: Blocks Na+/Cl- transport in Loop of Henle → Oedema/Cystic changes in Stria Vascularis.
• Effect: Usually Reversible. (Permanent if renal failure present).

3. Salicylates (Aspirin) & NSAIDs

• Symptoms: Tinnitus, Bilateral SNHL (High frequencies).
• Mechanism: Enzymatic interference (No morphological hair cell damage seen).
• Effect: Reversible upon discontinuation.
• Other NSAIDs: Naproxen, Piroxicam, Ketorolac.

4. Quinine & Chloroquine

Effect: Vasoconstriction in small vessels of cochlea/stria vascularis.

• Usually reversible (Higher doses → Permanent).
• Teratogenic: Congenital deafness/hypoplasia if mother takes in 1st trimester.

5. Cytotoxic Drugs

• Drugs: Nitrogen mustard, Cisplatin, Carboplatin.
• Damage: Outer hair cells of cochlea (Permanent).

6. Deferoxamine

• Use: Iron-chelating agent (Thalassaemia).
• Effect: High-frequency SNHL (Sudden or Delayed).
• Reversibility: Permanent (sometimes reversible).
• Toxicity is to nerves; children affected more.

7. Topical Ear Drops

Absorption occurs through Oval and Round windows if TM is perforated.