A 28-year-old construction worker from Kerala presents with high fever, jaundice, oliguria, and pulmonary hemorrhage on day 10 of illness. Blood and CSF cultures are positive for Leptospira interrogans. What is the drug of choice for severe leptospirosis (Weil's disease) with renal and CNS involvement?

Explanation

## Drug of Choice for Severe Leptospirosis (Weil's Disease) **Key Point:** Penicillin G is the drug of choice for severe leptospirosis (Weil's disease) with multi-organ involvement, particularly when renal failure, jaundice, or CNS manifestations (meningitis) are present. ### Clinical Context: Weil's Disease Weil's disease represents the severe, immune-phase manifestation of leptospirosis (typically after day 7 of illness), characterized by: - Renal failure (oliguria/anuria) - Hepatic dysfunction (jaundice) - Pulmonary hemorrhage - Leptospiral meningitis - Hemorrhagic manifestations ### Rationale for Penicillin G | Feature | Penicillin G | Doxycycline | Cephalosporins | |---------|-------------|------------|----------------| | **Phase of use** | Immune phase (late) | Leptospiremic (early) | Immune phase (alternative) | | **Route** | IV only | Oral | Oral/IV | | **CNS penetration** | Excellent (meningitis) | Poor | Good | | **Renal clearance** | Requires adjustment | Minimal adjustment | Requires adjustment | | **First-line status** | Yes (severe disease) | Yes (early disease) | Alternative | **High-Yield:** The timing of antibiotic therapy is critical—doxycycline works in the leptospiremic phase (days 1–7), while penicillin G is effective in the immune phase (after day 7) when antibodies develop and leptospires sequester in tissues. **Clinical Pearl:** Penicillin G achieves high CSF concentrations and is essential for leptospiral meningitis. The patient's day 10 presentation with meningitis (CSF culture positive) mandates penicillin G. **Mnemonic:** **WEIL = Weeks 2 + Penicillin** — Weil's disease (second week) requires Penicillin G, not doxycycline. ### Dosing for Severe Leptospirosis - **Penicillin G:** 18–24 million units daily IV in divided doses for 7–10 days - **Alternative (if penicillin allergy):** Ceftriaxone 1 g IV 6-hourly or cefotaxime 2 g IV 4–6 hourly **Warning:** Doxycycline is ineffective in the immune phase because leptospires are no longer in the bloodstream; they have sequestered in tissues and CSF. Starting doxycycline on day 10 would be inappropriate and ineffective.