Recommended Antibiotic Doses for Bacterial Meningitis
The recommended empiric antibiotic regimen for bacterial meningitis in adults under 60 years is ceftriaxone 2g IV every 12 hours or cefotaxime 2g IV every 6 hours, while adults 60 years or older should receive the same plus amoxicillin 2g IV every 4 hours. 1
Empiric Therapy Recommendations
Adults under 60 years:
- Preferred choice: Ceftriaxone 2g IV every 12 hours OR Cefotaxime 2g IV every 6 hours 1
- Alternative: Chloramphenicol 25 mg/kg IV every 6 hours (if cephalosporins contraindicated) 1
Adults 60 years or older:
- Preferred choice: Ceftriaxone 2g IV every 12 hours OR Cefotaxime 2g IV every 6 hours PLUS Amoxicillin 2g IV every 4 hours 1
- Alternative: Chloramphenicol 25 mg/kg IV every 6 hours AND Co-trimoxazole 10-20 mg/kg (of trimethoprim component) in four divided doses 1
Special considerations:
- Add vancomycin 15-20 mg/kg IV every 12 hours OR rifampicin 600 mg twice daily if penicillin-resistant pneumococci is suspected (e.g., recent travel to areas with high resistance rates) 1, 2
- For pediatric patients with meningitis: 100 mg/kg/day of ceftriaxone (not exceeding 4 grams daily) or cefotaxime 200 mg/kg/day divided every 6 hours 3, 4, 5
Pathogen-Specific Therapy
Streptococcus pneumoniae:
- Penicillin-sensitive (MIC ≤ 0.06 mg/L): Benzylpenicillin 2.4g IV every 4 hours OR continue ceftriaxone/cefotaxime at doses above 1, 6
- Penicillin-resistant but cephalosporin-sensitive: Continue ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 6 hours 1, 6
- Penicillin and cephalosporin-resistant: Continue ceftriaxone/cefotaxime PLUS vancomycin 15-20 mg/kg IV every 12 hours PLUS rifampicin 600 mg IV/orally twice daily 1, 6, 2
Neisseria meningitidis:
- Continue ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 6 hours 1
- Alternative: Benzylpenicillin 2.4g IV every 4 hours 1
Staphylococcal meningitis:
- Methicillin-susceptible: Nafcillin or oxacillin 6
- Methicillin-resistant: Vancomycin 15-20 mg/kg IV every 8-12 hours, consider adding rifampicin 600 mg twice daily 6, 2
Duration of Therapy
- Pneumococcal meningitis: 10 days if recovered by day 10; 14 days if not recovered by day 10 or if penicillin/cephalosporin resistant 1, 6, 7
- Meningococcal meningitis: 7-10 days 1
- Staphylococcal meningitis: 14 days 6, 7
- Enterobacteriaceae: 21 days 7
Monitoring and Adjustments
- Monitor clinical response daily (fever, neck stiffness, mental state) 7
- For vancomycin therapy, maintain serum trough levels of 15-20 μg/mL 2
- Consider repeat CSF analysis if no clinical improvement after 48-72 hours 7, 2
Important Caveats and Considerations
- Third-generation cephalosporins are the empirical antibiotics of choice in most settings with low resistance rates due to their bactericidal activity and meningeal penetration 1
- The addition of vancomycin is crucial when penicillin-resistant pneumococci cannot be ruled out, particularly in regions with high resistance rates 2, 8
- For post-neurosurgical meningitis, consider vancomycin plus either cefepime, ceftazidime, or meropenem 6
- In neonates, ceftriaxone should be administered over 60 minutes to reduce the risk of bilirubin encephalopathy 3
- For infants under 3 months, ampicillin plus cefotaxime is recommended as empiric therapy to cover Listeria monocytogenes 9
- Vancomycin should not be used as monotherapy due to variable CSF penetration 10