Meningitis: Treatment, Drug of Choice, and Drug Details

Overview

• Type (bacterial, viral, fungal, tubercular)
• Patient age and immune status
• Causative organism (if known)

1. BACTERIAL MENINGITIS

Empiric Therapy (Before Culture Results)

2. PATHOGEN-SPECIFIC (Definitive) THERAPY

A. Streptococcus pneumoniae (Pneumococcal Meningitis)

• Susceptible strains (cefotaxime/ceftriaxone MIC ≤1.0 mcg/mL): Ceftriaxone or Cefotaxime alone
• Penicillin-resistant or cephalosporin-resistant strains: Vancomycin + Ceftriaxone (or Cefotaxime)
• Highly resistant strains: Vancomycin + Rifampin IV
• Note: When dexamethasone is co-administered, CSF vancomycin levels may be reduced - monitor closely.

B. Neisseria meningitidis (Meningococcal Meningitis)

• Drug of choice: Penicillin G IV or Ampicillin (susceptible strains)
• Resistant strains or empiric: Ceftriaxone (7-day course is sufficient)
• Chemoprophylaxis for close contacts: Rifampin oral (or ciprofloxacin, ceftriaxone single dose)

C. Listeria monocytogenes

• Drug of choice: Ampicillin 2g IV every 4 hours (for confirmed cases)
• For meningitis/endocarditis or severe T-cell impairment: Add Gentamicin (2 mg/kg IV load, then 1.7 mg/kg q8h; adjust for renal function)
• Duration: At least 3 weeks for meningitis; 2 weeks for bacteremia without CNS involvement
• Penicillin allergy alternative: TMP-SMX (5 mg/kg of trimethoprim component IV q6-8h) - as effective as ampicillin + gentamicin
• Cephalosporins are NOT effective against Listeria

D. Haemophilus influenzae

• Drug of choice: Cefotaxime or Ceftriaxone
• Alternative: Cefepime, or Chloramphenicol + Ampicillin (if susceptible)
• Duration: 10-day course

E. Staphylococcal Meningitis

• MSSA: Nafcillin or Oxacillin
• MRSA or penicillin allergy: Vancomycin is the treatment of choice
• If CSF cultures remain positive after 48h IV vancomycin: Add intrathecal vancomycin (preservative-free)
• If beta-lactams and vancomycin cannot be used: Linezolid, Daptomycin, or TMP-SMX
• Add Rifampin in severe/refractory cases, or when intracranial hardware is present

F. Gram-negative bacilli / P. aeruginosa (Post-neurosurgical)

• Meropenem or Cefepime + Vancomycin
• Ceftazidime can be used for Pseudomonas coverage
• Meropenem is active against L. monocytogenes, P. aeruginosa, and penicillin-resistant pneumococci

3. ADJUNCTIVE THERAPY - DEXAMETHASONE

• Indication: Suspected or proven pneumococcal meningitis; H. influenzae in children
• Dose: 10 mg IV every 6 hours for 4 days (adults); alternatively 0.15 mg/kg IV q6h x 4 days in children
• Timing: Must be given before or with the first antibiotic dose to be effective
• Benefits: Reduces CSF inflammation, decreases mortality in adults, reduces hearing loss and neurologic sequelae in children
• Caution: Concomitant dexamethasone reduces CSF vancomycin penetration - consider stopping if non-pneumococcal pathogen is confirmed

4. VIRAL MENINGITIS

• Most cases (especially enteroviral) are self-limiting - no specific antiviral needed
• Herpes simplex encephalitis/meningitis: Drug of choice = Acyclovir 10 mg/kg IV every 8 hours (add empirically when HSV is in the differential)
• Varicella-zoster meningitis: Acyclovir IV
• CMV: Ganciclovir + Foscarnet (in immunocompromised)

5. FUNGAL MENINGITIS

Cryptococcus neoformans (most common fungal meningitis, esp. in HIV)

• Induction: Amphotericin B deoxycholate 0.7-1 mg/kg/day IV + Flucytosine 25 mg/kg PO q6h x 2 weeks
• Consolidation: Fluconazole 400 mg/day x 8 weeks
• Maintenance: Fluconazole 200 mg/day (lifelong in HIV patients)

6. TUBERCULOUS (TB) MENINGITIS

• Regimen: RIPE - Rifampin + Isoniazid + Pyrazinamide + Ethambutol (intensive phase 2 months)
• Continuation: Rifampin + Isoniazid x 9-12 months (total 12 months treatment)
• Adjunctive: Dexamethasone (reduces mortality and severe disability)

7. INCREASED ICP MANAGEMENT

• Head elevation to 30-45 degrees
• Intubation and hyperventilation (PaCO2 25-30 mmHg)
• Mannitol IV
• ICU monitoring; ICP monitoring device for accurate measurement

Summary: Drug of Choice by Organism