What is the empiric treatment for meningitis/encephalitis?

Empiric Treatment of Meningitis/Encephalitis

The empiric treatment for meningitis/encephalitis should include ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours as the cornerstone therapy, with additional agents based on age and risk factors. 1

First-Line Empiric Treatment Algorithm

For Adults <60 Years:

• Ceftriaxone 2g IV every 12 hours OR Cefotaxime 2g IV every 6 hours 2, 1
• If penicillin-resistant pneumococci is suspected (e.g., recent travel to areas with high resistance rates):
  • Add Vancomycin 15-20 mg/kg IV every 12 hours OR Rifampicin 600 mg twice daily 2

For Adults ≥60 Years or Immunocompromised:

• Ceftriaxone 2g IV every 12 hours OR Cefotaxime 2g IV every 6 hours
• PLUS Amoxicillin/Ampicillin 2g IV every 4 hours (for Listeria coverage) 2, 1
• If penicillin-resistant pneumococci is suspected:
  • Add Vancomycin 15-20 mg/kg IV every 12 hours OR Rifampicin 600 mg twice daily 2

For Severe Penicillin/Cephalosporin Allergy:

• Chloramphenicol 25 mg/kg IV every 6 hours 2, 1
• For patients ≥60 years: Add Co-trimoxazole 10-20 mg/kg (of trimethoprim component) in four divided doses 2

Adjunctive Therapy

Corticosteroids:

• Dexamethasone 10mg IV every 6 hours for 4 days, starting before or with the first antibiotic dose 1
• Consider stopping if the causative organism is neither H. influenzae nor S. pneumoniae

Duration of Treatment

Based on Identified Pathogen:

• Pneumococcal meningitis:
  • Penicillin-sensitive: 10 days 2, 1
  • Penicillin-resistant: 14 days 1
• Meningococcal meningitis: 7 days 1
• Culture-negative cases: at least 14 days 1

Treatment Modifications Based on Culture Results

For Pneumococcal Meningitis:

• If penicillin-sensitive (MIC ≤0.06 mg/L): Continue ceftriaxone/cefotaxime OR switch to benzylpenicillin 2.4g IV every 4 hours 2
• If penicillin-resistant but cephalosporin-sensitive: Continue ceftriaxone/cefotaxime 2
• If resistant to both penicillin and cephalosporins: Continue ceftriaxone/cefotaxime PLUS vancomycin 15-20 mg/kg IV every 12 hours PLUS rifampicin 600 mg twice daily 2, 1, 3

Special Considerations

Administration:

• Administer ceftriaxone intravenously over 30 minutes (60 minutes in neonates) 4
• Avoid mixing ceftriaxone with calcium-containing solutions 4

Common Pitfalls to Avoid:

1. Delayed antibiotic administration: This significantly increases mortality risk. Start empiric therapy immediately after obtaining CSF samples (if possible) or even before lumbar puncture if there will be a delay 1

2. Inadequate Listeria coverage: Failing to add ampicillin/amoxicillin in patients ≥60 years or immunocompromised 2, 1

3. Overlooking resistant organisms: Not adding vancomycin when there's risk of resistant pneumococci 1, 3, 5

4. Premature discontinuation: Stopping antibiotics too early before completing the recommended duration based on the identified pathogen 1

5. Failure to adjust therapy: Not modifying treatment based on culture results and susceptibility patterns 2, 1

The combination of vancomycin and ceftriaxone has been shown to be synergistic against resistant pneumococcal strains, making this combination particularly effective for empiric therapy until susceptibility results are available 3, 5. Studies have demonstrated that CSF from patients receiving ceftriaxone alone may be unable to kill intermediately ceftriaxone-resistant or fully resistant pneumococcal strains when the concentration of ceftriaxone in the CSF is suboptimal 5.

While newer agents like meropenem and cefepime have shown efficacy in bacterial meningitis 6, 7, the current guidelines still recommend third-generation cephalosporins as first-line agents due to their established efficacy and safety profile 2, 1.