A 28-year-old woman presents with recurrent meningococcal meningitis (second episode in 18 months). Serology confirms complement deficiency. Which drug is the first-line prophylactic agent to prevent recurrent meningococcal disease in this patient?

Explanation

## Prophylaxis in Complement Deficiency–Associated Meningococcal Disease ### Clinical Context Patients with terminal complement deficiencies (C5–C9, properdin) have a markedly increased risk of recurrent *Neisseria meningitidis* infection. Prophylaxis is mandatory in these patients. ### Drug of Choice: Rifampicin **Key Point:** Rifampicin is the first-line prophylactic agent for meningococcal disease in complement-deficient patients because it achieves high cerebrospinal fluid (CSF) penetration and effectively eradicates nasopharyngeal carriage of *N. meningitidis*. **High-Yield:** Rifampicin dosing for prophylaxis: - Adults: 600 mg once daily for 2 days (or 10 mg/kg/day for 2 days) - Children: 10 mg/kg/day for 2 days - Eliminates carriage in >90% of cases ### Why Rifampicin Works 1. Excellent CSF penetration (achieves 20–40% of serum levels) 2. Bactericidal against meningococci 3. Eradicates nasopharyngeal carriage (prevents transmission and recurrent infection) 4. Short course (2 days) improves compliance ### Comparison with Other Agents | Agent | CSF Penetration | Eradicates Carriage | Role | |-------|-----------------|--------------------|-----------| | **Rifampicin** | Excellent (20–40%) | Yes (>90%) | **First-line prophylaxis** | | Penicillin V | Poor | No | Acute treatment only; does NOT eradicate carriage | | Ceftriaxone | Good | Partial (~50%) | Acute treatment; not ideal for prophylaxis | | Ciprofloxacin | Excellent | Yes (>95%) | Alternative if rifampicin contraindicated; less preferred in India due to resistance patterns | **Clinical Pearl:** Complement-deficient patients should also receive meningococcal vaccination (MCV4 or MenB), but vaccination alone is insufficient — chemoprophylaxis is still required. ### Additional Considerations - Vaccination status does not eliminate the need for prophylaxis - Close contacts of meningococcal cases also require prophylaxis (same regimen) - Counsel patient on drug interactions (rifampicin induces CYP3A4, affecting oral contraceptives and other drugs) [cite:Harrison 21e Ch 297]