Is streptomycin (antibiotic) ototoxic?

Streptomycin Ototoxicity

Streptomycin is definitively ototoxic, with vestibular toxicity exceeding its cochlear toxicity potential, causing irreversible damage to the vestibular branch of the eighth cranial nerve. 1, 2

Mechanism and Clinical Manifestations

Streptomycin causes ototoxicity through:

• Irreversible vestibulocochlear nerve damage 1
• Free radical generation within the inner ear 3
• Permanent damage to sensory cells and neurons 3

The clinical manifestations include:

• Vestibular symptoms: Vertigo, ataxia, nystagmus, disequilibrium (more common) 2
• Auditory symptoms: Tinnitus, hearing loss (particularly high-frequency) 1
• Early warning signs: Headache, nausea, vomiting 1

Risk Factors

The degree of ototoxicity is directly proportional to:

• Dose and duration of streptomycin administration 1
• Advanced age 2, 1
• Impaired renal function 2, 1
• Pre-existing auditory dysfunction 1
• Genetic predisposition (mitochondrial DNA variants, particularly m.1555A>G) 1, 4

Potentiating Factors

Ototoxicity risk increases with concurrent use of:

• Loop diuretics (furosemide, ethacrynic acid) 2, 1
• Mannitol 1
• Other aminoglycosides 1

Monitoring and Prevention

Recommended Monitoring

• Baseline audiometry and vestibular testing before treatment 2, 1
• Regular audiometric testing during treatment 5
• Monthly assessments of renal function 2
• Monthly questioning regarding auditory or vestibular symptoms 2
• Final audiometry review 2 months after the final dose 5

Definition of Ototoxicity on Audiogram

• 20 dB loss from baseline at any one test frequency, OR
• 10 dB loss at any two adjacent test frequencies 5

Prevention Strategies

• Use lowest effective dose for shortest duration possible 5
• Adjust dosing in patients with renal impairment 2
• Maintain adequate hydration during treatment 5
• Consider alternative antibiotics in high-risk patients 5
• Anti-free radical agents (e.g., salicylate) may attenuate ototoxic effects 3

Special Considerations

Pregnancy

Streptomycin is contraindicated in pregnancy due to:

• Readily crossing the placental barrier 1
• Risk of fetal hearing loss, especially in second and third trimesters 2, 1

Genetic Testing

Consider genetic testing for mitochondrial DNA variants in:

• Patients with family history of aminoglycoside ototoxicity 1
• Maternal history of hearing loss after aminoglycoside use 1

Clinical Approach to Suspected Ototoxicity

If symptoms of ototoxicity develop:

1. Immediately discontinue streptomycin 1
2. Perform audiometric and vestibular testing 2
3. Consider alternative antibiotics based on sensitivity testing
4. Early discontinuation may permit recovery before irreversible damage occurs 1

Despite its ototoxicity, streptomycin continues to have therapeutic applications in specific conditions, including tuberculosis treatment and management of Meniere's disease 6, but requires careful monitoring and risk assessment.