Should you continue using streptomycin in the presence of hearing loss?

Discontinue Streptomycin Immediately When Hearing Loss Occurs

Streptomycin should be discontinued immediately if any signs of hearing loss or vestibular dysfunction occur, as continued use can lead to irreversible ototoxicity. 1 The ototoxic effects of streptomycin are directly proportional to the dose and duration of administration, with vestibular toxicity being more prominent than cochlear toxicity.

Mechanism and Risk of Streptomycin-Induced Ototoxicity

Streptomycin, an aminoglycoside antibiotic used in treating non-tuberculous mycobacterial (NTM) infections, has significant ototoxic potential:

• Vestibular dysfunction manifests as headache, nausea, vomiting, and disequilibrium 1
• Cochlear damage presents as hearing loss, particularly affecting high frequencies first 1
• Risk factors for increased ototoxicity include:
  • Advanced age
  • Impaired renal function
  • Pre-existing auditory dysfunction
  • Concurrent use of other ototoxic medications (especially loop diuretics) 1, 2
  • Genetic predisposition (mitochondrial DNA variants, particularly m.1555A>G) 1

Monitoring Recommendations

The British Thoracic Society guidelines recommend comprehensive monitoring for patients receiving streptomycin:

• Baseline audiometry before starting treatment 3
• Regular audiometric testing during treatment (frequency based on risk and symptoms) 3
• Patient education about symptoms requiring immediate discontinuation (tinnitus, vestibular disturbance, hearing loss) 3
• Ototoxicity on audiogram is defined as a 20 dB loss from baseline at any one test frequency or a 10 dB loss at any two adjacent test frequencies 3

Management of Streptomycin-Induced Hearing Loss

When hearing loss is detected:

1. Discontinue streptomycin immediately 3, 1
2. Seek expert advice to consider a regimen change 3
3. Be aware that hearing loss that has already occurred is likely to be permanent 3, 4
4. Consider alternative antimicrobials for NTM treatment

Alternative Treatment Considerations

For patients with NTM pulmonary disease requiring aminoglycoside therapy:

• Some experts prefer amikacin over streptomycin due to a perceived difference in the severity of vestibular toxicity 3
• For older patients or those requiring long-term parenteral therapy, dose reduction may be necessary (8-10 mg/kg two to three times weekly, with maximum 500 mg for patients older than 50 years) 3
• Alternative regimens without aminoglycosides may be considered, particularly for patients with mild disease or medication intolerance 3

Important Caveats

• Vestibular symptoms generally appear early but may be reversible if detected early and the drug is discontinued 1
• Gross vestibular symptoms usually disappear 2-3 months after stopping the drug, but some impairment may persist 1
• Hearing loss can worsen even after the drug is withdrawn 2
• Studies have shown that prolonged streptomycin administration in adults causes significant persistent hearing loss, especially in high frequencies 5

Conclusion

The evidence clearly indicates that streptomycin should be discontinued at the first sign of hearing loss or vestibular dysfunction. The risk of permanent ototoxicity outweighs the potential benefits of continuing therapy, especially when alternative treatment options are available. Regular monitoring and patient education about warning symptoms are essential components of care when administering streptomycin.