Amoxicillin (Amoxil/Dymox) for Bacterial Meningitis
Amoxicillin is used to treat bacterial meningitis, but only in specific clinical scenarios: it is essential for neonates under 1 month old (combined with cefotaxime) and for patients aged ≥60 years or immunocompromised adults (combined with a third-generation cephalosporin) to provide coverage against Listeria monocytogenes. 1
Age-Based Treatment Algorithms
Neonates (<1 month old)
- Amoxicillin/ampicillin PLUS cefotaxime is the standard empiric regimen 1
- Dosing for age <1 week: amoxicillin 50 mg/kg IV every 8 hours 1
- Dosing for age 1-4 weeks: ampicillin 50 mg/kg IV every 6 hours 1
- This combination covers Group B Streptococcus, E. coli, and Listeria monocytogenes 1
Adults ≥60 Years Old
- Amoxicillin 2g IV every 4 hours MUST be added to ceftriaxone/cefotaxime 1
- This age group has increased risk of Listeria monocytogenes meningitis 1
- Third-generation cephalosporins alone do NOT cover Listeria 1
Immunocompromised Adults (Any Age)
- Amoxicillin 2g IV every 4 hours added to cephalosporin regimen 1
- Risk factors requiring Listeria coverage include: diabetes mellitus, immunosuppressive drugs, cancer, alcohol misuse 1
Children and Adults <50 Years (Without Risk Factors)
- Amoxicillin is NOT routinely used 1
- Third-generation cephalosporin (ceftriaxone or cefotaxime) alone is sufficient 1
- Add vancomycin or rifampicin only if local pneumococcal resistance rates are elevated 1
Historical Context and Current Position
While amoxicillin was studied as monotherapy for bacterial meningitis in the 1970s-1980s and showed comparable efficacy to ampicillin for H. influenzae and S. pneumoniae meningitis 2, 3, current guidelines have relegated amoxicillin to a combination role rather than monotherapy 1. Third-generation cephalosporins have superior CSF penetration and broader coverage, making them the empiric backbone for most age groups 1.
Critical Pitfalls to Avoid
- Never use amoxicillin as monotherapy for meningitis in modern practice - third-generation cephalosporins are superior 1
- Do not omit amoxicillin in patients ≥60 years or immunocompromised - Listeria coverage is life-saving 1
- Do not substitute amoxicillin for the cephalosporin component - it lacks adequate coverage for common pathogens like S. pneumoniae and N. meningitidis in the current resistance era 1
- Ensure treatment begins within 1 hour of presentation regardless of imaging or lumbar puncture completion 1, 4
When Amoxicillin is Contraindicated
If clear anaphylaxis history to penicillins exists, use IV chloramphenicol 25 mg/kg every 6 hours as alternative empiric therapy 1