Aminoglycosides cause irreversible ototoxicity through which primary mechanism?

Explanation

## Aminoglycoside Ototoxicity Mechanism **Key Point:** Aminoglycosides accumulate in the inner ear (cochlea and vestibule) and generate reactive oxygen species (ROS), leading to oxidative damage and irreversible destruction of cochlear and vestibular hair cells. ### Pathophysiology of Ototoxicity 1. **Aminoglycoside accumulation:** Aminoglycosides bind to ribosomes in mitochondria of cochlear hair cells, causing preferential uptake and accumulation. 2. **ROS generation:** The drug-ribosome complex catalyzes the formation of hydroxyl radicals and other free radicals. 3. **Hair cell apoptosis:** Oxidative stress triggers mitochondrial dysfunction, energy depletion, and programmed cell death of inner ear hair cells. 4. **Irreversibility:** Hair cell loss is permanent because mammalian cochlear hair cells do not regenerate. **High-Yield:** The ototoxicity is **dose-dependent and cumulative** — risk increases with: - High peak serum concentrations - Prolonged therapy (>7–10 days) - Pre-existing renal impairment (drug accumulation) - Concurrent use of other ototoxic agents (loop diuretics, NSAIDs, cisplatin) - Advanced age - Genetic predisposition (mitochondrial mutations) **Clinical Pearl:** Vestibulotoxicity (vertigo, ataxia) typically precedes auditory toxicity. Monitoring for dizziness or balance disturbance during therapy is an early warning sign. **Mnemonic — "OTOTOXIC drugs":** **O**xidative stress, **T**oxin accumulation in inner ear, **O**xidative phosphorylation disrupted, **T**iming (cumulative), **O**lder patients at risk, **X**enobiotics (aminoglycosides), **I**rreversible hair cell loss, **C**ochlear and vestibular damage.