Is streptomycin (streptomycin) used to treat central nervous system (CNS) tuberculosis (TB)?

Streptomycin in CNS Tuberculosis Treatment

Streptomycin should not be used as a first-line agent for CNS tuberculosis due to its poor penetration into the cerebrospinal fluid, but may be considered as a fourth drug option in the initial phase of treatment when the meninges are inflamed. 1, 2

Role of Streptomycin in CNS TB Treatment

Streptomycin has historically been used in tuberculosis treatment, but its use in CNS tuberculosis is limited by several important factors:

CSF Penetration

• Streptomycin has poor penetration into the cerebrospinal fluid, even in patients with meningitis 1, 3
• It only penetrates in adequate concentrations when the meninges are inflamed in the early stage of treatment 1, 2
• According to pharmacokinetic studies, streptomycin and other aminoglycosides have poor CSF penetration compared to other anti-TB medications 3

Recommended Treatment Regimen for CNS TB

The standard treatment regimen for CNS tuberculosis consists of:

1. Initial phase (first 2 months):

   • Rifampicin
   • Isoniazid
   • Pyrazinamide
   • Fourth drug (ethambutol OR streptomycin) 1, 2

2. Continuation phase (next 10 months):

   • Rifampicin
   • Isoniazid 2

Drug Selection Considerations

When selecting the fourth drug for the initial phase:

• Isoniazid, pyrazinamide, and prothionamide/ethionamide penetrate well into the CSF 1, 3
• Rifampicin penetrates less well 1, 3
• Ethambutol and streptomycin have poor CSF penetration 1, 3

Clinical Guidance for Streptomycin Use

When to Consider Streptomycin

• As a fourth drug option in the initial phase of treatment 1, 2
• In cases where ethambutol cannot be used due to contraindications 1
• When visual acuity cannot be monitored in unconscious patients (Stage III meningitis), as ethambutol requires visual monitoring 1

Dosing Recommendations

According to the FDA label for streptomycin 4:

• Adults: 15 mg/kg daily (maximum 1g) or 25-30 mg/kg twice/thrice weekly (maximum 1.5g)
• Children: 20-40 mg/kg daily (maximum 1g) or 25-30 mg/kg twice/thrice weekly (maximum 1.5g)

Important Cautions

• Streptomycin is contraindicated in pregnancy due to risk of fetal hearing loss 1, 4
• Reduced doses are required in patients with renal impairment 1, 4
• In patients older than 60 years, the dose should be reduced due to increased toxicity risk 4
• Monitor for ototoxicity (vestibular and hearing disturbances) and nephrotoxicity 4

Alternative Approaches

For CNS tuberculosis treatment, drugs with better CSF penetration should be prioritized:

• Fluoroquinolones (particularly levofloxacin and moxifloxacin) demonstrate high CSF penetration and may be more useful than streptomycin for CNS TB 5, 6
• Ethionamide has good CSF penetration with concentrations equal to those in serum 1
• Corticosteroids are recommended as adjunctive therapy for moderate to severe disease (stages II and III) 1, 2

Treatment Duration

• CNS tuberculosis requires longer treatment duration (12 months) compared to pulmonary TB (6 months) 1, 2
• If pyrazinamide is omitted or cannot be tolerated, treatment should be extended to 18 months 1, 2

Conclusion

While streptomycin is listed as a potential fourth drug option in the initial treatment phase of CNS tuberculosis, its poor CSF penetration makes it less ideal than alternatives with better CNS penetration. The decision to use streptomycin should be based on drug susceptibility patterns, patient-specific factors, and the availability of alternatives with better CSF penetration.